Kawasaki, Shinji; Lin, Chengtian; Kuhns, Philip L; Reyes, Arneil P; Zheng, Guo-qing
2010-09-24
We report the results of the Knight shift by ⁶³,⁶⁵Cu-NMR measurements on single-layered copper-oxide Bi₂Sr(₂-x)La(x)CuO(₆+δ) conducted under very high magnetic fields up to 44 T. The magnetic field suppresses superconductivity completely, and the pseudogap ground state is revealed. The ⁶³Cu-NMR Knight shift shows that there remains a finite density of states at the Fermi level in the zero-temperature limit, which indicates that the pseudogap ground state is a metallic state with a finite volume of Fermi surface. The residual density of states in the pseudogap ground state decreases with decreasing doping (increasing x) but remains quite large even at the vicinity of the magnetically ordered phase of x ≥ 0.8, which suggests that the density of states plunges to zero upon approaching the Mott insulating phase.
Effective SU(2) theory for the pseudogap state
Montiel, X.; Kloss, T.; Pépin, C.
2017-03-01
This paper exposes in a detailed manner the recent findings about the SU(2) scenario for the underdoped phase of the cuprate superconductors. The SU(2) symmetry is formulated as a rotation between the d -wave superconducting (SC) phase and a d -wave charge order. We define the operators responsible for the SU(2) rotations and we derive the nonlinear σ model associated with it. In this framework, we demonstrate that SU(2) fluctuations are massless in finite portions of the Brillouin zone corresponding to the antinodal regions (0 ,π ) and (π ,0 ). We argue that the presence of SU(2) fluctuations in the antinodal region leads to the opening of Fermi arcs around the Fermi surface and to the formation of the pseudogap. Moreover, we show that SU(2) fluctuations lead, in turn, to the emergence of a finite momentum SC order—or pair density wave (PDW)—and more importantly to a new kind of excitonic particle-hole pairs liquid, the resonant excitonic state (RES), which is made of patches of preformed particle-hole pairs with multiple momenta. When the RES liquid becomes critical, we demonstrate that electronic scattering through the critical modes leads to anomalous transport properties. This new finding can account for the strange metal (SM) phase at finite temperature, on the right-hand side of the SC dome, shedding light on another notoriously mysterious part of the phase diagram of the cuprates.
Muon Knight shift study of pseudogap state in underdoped (Bi,Pb)2201
Energy Technology Data Exchange (ETDEWEB)
Miyazaki, M., E-mail: mmiya@post.kek.j [Department of Materials Structure Science, Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba, Ibaraki-Pref. 305-0801 (Japan); Kadono, R. [Department of Materials Structure Science, Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba, Ibaraki-Pref. 305-0801 (Japan); Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK-IMSS), 1-1 Oho, Tsukuba, Ibaraki-Pref. 305-0801 (Japan); Hiraishi, M.; Satoh, K.H. [Department of Materials Structure Science, Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba, Ibaraki-Pref. 305-0801 (Japan); Takeshita, S. [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK-IMSS), 1-1 Oho, Tsukuba, Ibaraki-Pref. 305-0801 (Japan); Koda, A. [Department of Materials Structure Science, Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba, Ibaraki-Pref. 305-0801 (Japan); Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK-IMSS), 1-1 Oho, Tsukuba, Ibaraki-Pref. 305-0801 (Japan); Fukunaga, Y.; Tanabe, Y.; Adachi, T.; Koike, Y. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)
2010-12-15
We performed zero-field muon spin rotation/relaxation (ZF-{mu}SR) measurements on high-quality single-crystalline samples of Bi{sub 1.76}Pb{sub 0.35}Sr{sub 1.89}CuO{sub 6+{delta}} [(Bi,Pb)2201] over a wide doping region controlled by oxygen depletion ({delta}). We find that there is no static magnetic order above {approx}2 K in any of these samples including underdoped samples. The absence of slow antiferromagnetic fluctuation in the underdoped region allows reliable muon Knight shift measurements, which provides a direct evidence of reduced density of states at lower temperatures or 'pseudogap'.
Fermi liquid behavior of the in-plane resistivity in the pseudogap state of YBa2Cu4O8.
Proust, Cyril; Vignolle, Baptiste; Levallois, Julien; Adachi, S; Hussey, Nigel E
2016-11-29
Our knowledge of the ground state of underdoped hole-doped cuprates has evolved considerably over the last few years. There is now compelling evidence that, inside the pseudogap phase, charge order breaks translational symmetry leading to a reconstructed Fermi surface made of small pockets. Quantum oscillations [Doiron-Leyraud N, et al. (2007) Nature 447(7144):565-568], optical conductivity [Mirzaei SI, et al. (2013) Proc Natl Acad Sci USA 110(15):5774-5778], and the validity of Wiedemann-Franz law [Grissonnache G, et al. (2016) Phys Rev B 93:064513] point to a Fermi liquid regime at low temperature in the underdoped regime. However, the observation of a quadratic temperature dependence in the electrical resistivity at low temperatures, the hallmark of a Fermi liquid regime, is still missing. Here, we report magnetoresistance measurements in the magnetic-field-induced normal state of underdoped YBa2Cu4O8 that are consistent with a T(2) resistivity extending down to 1.5 K. The magnitude of the T(2) coefficient, however, is much smaller than expected for a single pocket of the mass and size observed in quantum oscillations, implying that the reconstructed Fermi surface must consist of at least one additional pocket.
Observation of pseudogap in the normal state of superconducting Mo{sub 3}Sb{sub 7}
Energy Technology Data Exchange (ETDEWEB)
Tran, V.H. [Polish Academy of Sciences, Institute of Low Temperature and Structure Research, 50-422 Wroclaw (Poland); Batkova, M.; Batko, I.; Pribulova, Z. [Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Kosice (Slovakia); Bukowski, Z. [Laboratory for Solid State Physics, ETH Zuerich, 8093 Zuerich (Switzerland)
2010-03-15
Using electron tunneling spectroscopy, we investigated density of states of Mo{sub 3}Sb{sub 7} in the temperature range 1.7-60 K. The differential conductance dI/dV vs. V curve at 4.2 K shows that an energy pseudogap of 2{delta}{proportional_to} 15(2) meV is formed in the density of states. In the superconducting state, the tunneling spectra exhibit the presence of a BCS-type superconducting gap of {delta}{sub sc} (0) {proportional_to} 0.24 meV. Future investigations of the interplay between superconductivity and possible SDW ordering, and the anisotropic nature of the nesting of the Fermi surface in Mo{sub 3}Sb{sub 7} are highly desired. Tunneling spectra of Mo{sub 3}Sb{sub 7} measured in the normal state (a) and in the superconducting state (b). (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Bhalla, Pankaj; Singh, Navinder
2014-09-01
The frequency dependent scattering rate of generalized Drude model contains important information on the electronic structure and on scattering mechanism. In the present investigation, we study the frequency dependent scattering rate of cuprates (Mitrović-Fiorucci/Sharapov-Carbotte scattering rate) in the pseudogap phase using the non-constant energy dependent Yang-Rice-Zhang (YRZ) density of states. First, with the energy dependent density of states, the scattering rate shows a depression at low energy coming from the opening of the pseudogap. Second, the evolution of 1/ τ( ω,T) with temperature shows the observed increase in scattering rate with temperature at lower frequencies and the temperature independence of 1 / τ( ω) at higher frequencies. Third, the signature of the thresholds due to the boson density of states and to the electronic density of states are also observed. These signatures are qualitatively in accord with the experiments.
Evidence for a spin pseudogap in the normal state of superconducting Mo{sub 3}Sb{sub 7}
Energy Technology Data Exchange (ETDEWEB)
Tran, V H; Miiller, W [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wroclaw (Poland); Hillier, A D; Adroja, D T [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom); Bukowski, Z [Laboratory for Solid State Physics, ETH Zuerich, 8093 Zuerich (Switzerland)
2009-12-02
Using muon spin relaxation (muSR) and inelastic neutron scattering (INS) we have investigated the normal state of the superconductor Mo{sub 3}Sb{sub 7} and the reference compound Ru{sub 3}Sn{sub 7}. The muSR experiments on Ru{sub 3}Sn{sub 7} reveal static and relatively slow dynamic relaxations, which are ascribed to a random static nuclear dipole field and thermally activated muon motion, respectively. INS experiments on Ru{sub 3}Sn{sub 7}, on the other hand, reveal three phononic excitations at 11, 18 and 23 meV, substantiating the assertion of Einstein and Debye oscillations derived from the specific heat and electrical resistivity data. The distinct difference in the muSR as well as INS spectra between Ru{sub 3}Sn{sub 7} and Mo{sub 3}Sb{sub 7} provides strong evidence for a magnetic/electronic nature of the phase transition at T{sup *} = 50 K in the Mo-based compound. On the basis of the muSR and INS data, the energy spin pseudogap of 150(10) K was estimated. The observed weak magnetism in the dynamic susceptibility chi{sup ''}(Q,omega) and residual longitudinal field relaxation at 5 K imply a static ordering or quantum fluctuations.
Parker, Colin; Pushp, Aakash; Pasupathy, Abhay; Gomes, Kenjiro; Ono, Shimpei; Ando, Yoichi; Wen, Jinsheng; Xu, Zhijun; Gu, Genda; Yazdani, Ali
2010-03-01
Spatial modulations in the local density of states of the high temperature superconductor Bi2Sr2CaCu208+δ have now been reported both above and below Tc. At low energies and low temperatures, these modulations have been attributed to the so-called octet model of Bogoliubov Quasiparticle Interference (BQPI). At temperatures above Tc, non-dispersive modulations were found near optimal doping, suggestive of a translation symmetry breaking ordered state[1]. Recent observations of low energy, dispersive modulations above Tc in a highly underdoped sample have been taken as evidence for Bogoliubov excitations above Tc[2]. We extend these measurements to a regime where we know from other measurements, such as anomalous diamagnetism, that there are no superconducting correlations in order to clarify whether any aspects of these modulations are related to superconducting correlations or to potential ordering at T*. [1] M. Vershinin, et al. Science 305, 1993 (2004) [2] J. Lee, et al. Science 325, 1099 (2009)
Singlet Ground State Magnetism:
DEFF Research Database (Denmark)
Loidl, A.; Knorr, K.; Kjems, Jørgen
1979-01-01
The magneticGamma 1 –Gamma 4 exciton of the singlet ground state system TbP has been studied by inelastic neutron scattering above the antiferromagnetic ordering temperature. Considerable dispersion and a pronounced splitting was found in the [100] and [110] directions. Both the band width and th...
Gaps and pseudogaps in perovskite rare earth nickelates
Directory of Open Access Journals (Sweden)
S. James Allen
2015-06-01
Full Text Available We report on tunneling measurements that reveal the evolution of the quasiparticle state density in two rare earth perovskite nickelates, NdNiO3 and LaNiO3, that are close to a bandwidth controlled metal to insulator transition. We measure the opening of a sharp gap of ∼30 meV in NdNiO3 in its insulating ground state. LaNiO3, which remains a correlated metal at all practical temperatures, exhibits a pseudogap of the same order. The results point to both types of gaps arising from a common origin, namely, a quantum critical point associated with the T = 0 K metal-insulator transition. The results support theoretical models of the quantum phase transition in terms of spin and charge instabilities of an itinerant Fermi surface.
Gaps and pseudogaps in perovskite rare earth nickelates
Energy Technology Data Exchange (ETDEWEB)
Allen, S. James; Ouellette, Daniel G.; Kally, James; Kozhanov, Alex [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Hauser, Adam J.; Mikheev, Evgeny; Zhang, Jack Y.; Moreno, Nelson E.; Son, Junwoo; Stemmer, Susanne [Materials Department, University of California, Santa Barbara, California 93106 (United States); Balents, Leon [Department of Physics, University of California, Santa Barbara, California 93106 (United States); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States)
2015-06-01
We report on tunneling measurements that reveal the evolution of the quasiparticle state density in two rare earth perovskite nickelates, NdNiO{sub 3} and LaNiO{sub 3}, that are close to a bandwidth controlled metal to insulator transition. We measure the opening of a sharp gap of ∼30 meV in NdNiO{sub 3} in its insulating ground state. LaNiO{sub 3}, which remains a correlated metal at all practical temperatures, exhibits a pseudogap of the same order. The results point to both types of gaps arising from a common origin, namely, a quantum critical point associated with the T = 0 K metal-insulator transition. The results support theoretical models of the quantum phase transition in terms of spin and charge instabilities of an itinerant Fermi surface.
Lonchakov, A. T.; Marchenkov, V. V.; Okulov, V. I.; Okulova, K. A.
2013-01-01
New experimental evidence is obtained on the physical nature of the semiconducting properties of Fe2-xV1+xAl alloys with near-stoichiometric (x = 0) compositions. We examine the low-temperature thermal emf of two alloys: one is enriched in vanadium and exhibits a pseudogap in the electron density of states at the Fermi energy, while in the other, which is depleted in vanadium, the scattering of electrons by localized spins has a stronger influence. The experimental temperature dependences of the thermal emf at low temperatures display some characteristic anomalies that are observed here for the first time and are manifestations of these two effects. Existing theory is used to interpret the anomalous contributions of both effects (types), determine their characteristic parameters, and establish the conditions under which they appear in V-depleted and V-enriched alloys. Data on the thermal emf in magnetic fields show that that the thermal emf decreases substantially as the magnetic field is increased, confirming the key role of the mechanism of current carrier scattering by localized moments.
Evidence for a pseudogap above T{sub c} in underdoped superconductors
Energy Technology Data Exchange (ETDEWEB)
Mesot, J.; Boettger, G.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Berastegui, P.; Mutka, H. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)
1997-09-01
Our measurements of the temperature dependence of the relaxation rate of crystal field excitations in underdoped high temperature superconductors show clear evidences for the opening of a pseudogap in the normal state. The critical temperature related to the opening of the pseudogap appears to be extremely dependent upon the energy window at which the static susceptibility is being probed. (author) 2 figs., 4 refs.
The origin of the pseudogap in α-Ga
Zhu, Zhiyong
2011-11-10
Density functional theory, the free-electron empty lattice approximation and the nearly free-electron approximation are employed to investigate the electronic properties of partially covalent α-Ga. Whereas free-electron-like properties are revealed over a large energy range, a deep pseudogap at the Fermi level is characteristic of α-Ga. We explain the origin of the pseudogap in terms of a delicate interplay between the electronic states and the specific Brillouin zone geometry. © 2011 IOP Publishing Ltd.
Dirac cone and pseudogapped density of states in the topological half-Heusler compound YPtBi
Kronenberg, A.; Braun, J.; Minár, J.; Elmers, H.-J.; Kutnyakhov, D.; Zaporozhchenko, A. V.; Wallauer, R.; Chernov, S.; Medjanik, K.; Schönhense, G.; Kläui, M.; Chadov, S.; Ebert, H.; Jourdan, M.
2016-10-01
Topological insulators (TIs) are exciting materials, which exhibit unprecedented properties, such as helical spin-momentum locking, which leads to large torques for magnetic switching and highly efficient spin current detection. Here we explore the compound YPtBi, an example from the class of half-Heusler materials, for which the typical band inversion of topological insulators was predicted. We prepared this material as thin films by conventional cosputtering from elementary targets. By in situ time-of-flight momentum microscopy, a Dirac conelike surface state with a Dirac point ≃300 meV below the Fermi energy was observed, in agreement with electronic structure-photoemission calculations. Only little additional spectral weight due to other states was observed at EF, which corroborates the identification of the topologically protected surface state and is highly relevant for spintronics applications.
Features of pseudogap and superconductivity states of YBa sub 2 Cu sub 3 O sub 7 sub - sub x
Misochko, O V; Dekorsy, T; Helm, M
2002-01-01
The relaxation dynamics of the lattice and low-energy quasi-particles of the YBa sub 2 Cu sub 3 O sub 7 sub - sub x superconductor is studied through the light reflection method within the wide temperature range. It is shown that for T > T sub c there exist two areas of temperature with qualitatively and quantitatively different excitation dynamics and the transition between these areas is of the hysteresis character. It is established also, that the character of the change in the relaxation dynamics of the charge carriers in the superconducting state indicates the anisotropic gap with zeroes on the Fermi surface
ARPES Studies of Cuprate Fermiology: Superconductivity, Pseudogap and Quasiparticle Dynamics
Energy Technology Data Exchange (ETDEWEB)
Vishik, Inna
2011-06-23
We present angle-resolved photoemission spectroscopy (ARPES) studies of the cuprate high-temperature superconductors which elucidate the relation between superconductivity and the pseudogap and highlight low-energy quasiparticle dynamics in the superconducting state. Our experiments suggest that the pseudogap and superconducting gap represent distinct states, which coexist below T{sub c}. Studies on Bi-2212 demonstrate that the near-nodal and near-antinodal regions behave differently as a function of temperature and doping, implying that different orders dominate in different momentum-space regions. However, the ubiquity of sharp quasiparticles all around the Fermi surface in Bi-2212 indicates that superconductivity extends into the momentum-space region dominated by the pseudogap, revealing subtlety in this dichotomy. In Bi-2201, the temperature dependence of antinodal spectra reveals particle-hole asymmetry and anomalous spectral broadening, which may constrain the explanation for the pseudogap. Recognizing that electron-boson coupling is an important aspect of cuprate physics, we close with a discussion of the multiple 'kinks' in the nodal dispersion. Understanding these may be important to establishing which excitations are important to superconductivity.
Ultrasonic signatures at the superconducting and the pseudogap phase boundaries in YBCO cuprates.
Energy Technology Data Exchange (ETDEWEB)
Shehter, Arkady [Los Alamos National Laboratory; Migliori, Albert [Los Alamos National Laboratory; Betts, Jonathan B. [Los Alamos National Laboratory; Balakirev, Fedor F. [Los Alamos National Laboratory; McDonald, Ross David [Los Alamos National Laboratory; Riggs, Scott C. [Los Alamos National Laboratory; Ramshaw, Brad [University of British Columbia, Canada; Liang, Ruixing [University of British Columbia, Canada; Hardy, Walter N. [University of British Columbia, Canada; Bonn, Doug A. [University of British Columbia, Canada
2012-08-28
A major issue in the understanding of cuprate superconductors is the nature of the metallic state from which high temperature superconductivity emerges. Central to this issue is the pseudogap region of the doping-temperature phase diagram that extends from room temperature to the superconducting transition. Although polarized neutron scattering studies hint at magnetic order associated with the pseudogap, there is no clear thermodynamic evidence for a phase boundary. Such evidence has a straightforward physical interpretation, however, it is difficult to obtain over a temperature range wide enough to encompass both the pseudogap and superconducting phases. We address this by measuring the elastic response of detwinned single crystals, an underdoped YBCO{sub 6.60} with superconducting transition at T{sub c} = 61.6K and a slightly overdoped YBCO{sub 6.98} with T{sub c} = 88.0K. We observe a discontinuity in the elastic moduli across the superconducting transition. Its magnitude requires that pair formation is coincident with superconducting coherence (the onset of the Meissner effect). For both crystals the elastic response reveals a phase transition at the pseudogap boundary. In slightly overdoped YBCO that transition is 20K below T{sub c}, extending the pseudogap phase boundary inside the superconducting dome. This supports a description of the metallic state in cuprates where a pseudogap phase boundary evolves into a quantum critical point masked by the superconducting dome.
Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors
Lee, Patrick A.
2014-07-01
The enigmatic pseudogap phase in underdoped cuprate high-Tc superconductors has long been recognized as a central puzzle of the Tc problem. Recent data show that the pseudogap is likely a distinct phase, characterized by a medium range and quasistatic charge ordering. However, the origin of the ordering wave vector and the mechanism of the charge order is unknown. At the same time, earlier data show that precursive superconducting fluctuations are also associated with this phase. We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional Bardeen-Cooper-Schrieffer theory which pairs electrons on opposite sides of the Fermi surface. In this state the Cooper pair carries a net momentum and belongs to a general class called pair density wave. The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB) picture, where spinons traveling in the same direction feel an attractive force in analogy with Ampere's effects in electromagnetism. We call this Amperean pairing. Charge order automatically appears as a subsidiary order parameter even when long-range pair order is destroyed by phase fluctuations. Our theory gives a prediction of the ordering wave vector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. The Fermi arc, the unusual way the tip of the arc terminates, and the relation of the spanning vector of the arc tips to the charge ordering wave vector also come out naturally. Finally, we propose an experiment that can directly test the notion of Amperean pairing.
Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors
Directory of Open Access Journals (Sweden)
Patrick A. Lee
2014-07-01
Full Text Available The enigmatic pseudogap phase in underdoped cuprate high-T_{c} superconductors has long been recognized as a central puzzle of the T_{c} problem. Recent data show that the pseudogap is likely a distinct phase, characterized by a medium range and quasistatic charge ordering. However, the origin of the ordering wave vector and the mechanism of the charge order is unknown. At the same time, earlier data show that precursive superconducting fluctuations are also associated with this phase. We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional Bardeen-Cooper-Schrieffer theory which pairs electrons on opposite sides of the Fermi surface. In this state the Cooper pair carries a net momentum and belongs to a general class called pair density wave. The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB picture, where spinons traveling in the same direction feel an attractive force in analogy with Ampere’s effects in electromagnetism. We call this Amperean pairing. Charge order automatically appears as a subsidiary order parameter even when long-range pair order is destroyed by phase fluctuations. Our theory gives a prediction of the ordering wave vector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. The Fermi arc, the unusual way the tip of the arc terminates, and the relation of the spanning vector of the arc tips to the charge ordering wave vector also come out naturally. Finally, we propose an experiment that can directly test the notion of Amperean pairing.
On the ground state of metallic hydrogen
Chakravarty, S.; Ashcroft, N. W.
1978-01-01
A proposed liquid ground state of metallic hydrogen at zero temperature is explored and a variational upper bound to the ground state energy is calculated. The possibility that the metallic hydrogen is a liquid around the metastable point (rs = 1.64) cannot be ruled out. This conclusion crucially hinges on the contribution to the energy arising from the third order in the electron-proton interaction which is shown here to be more significant in the liquid phase than in crystals.
Review of pseudogaps in strongly interacting Fermi gases
Mueller, Erich J.
2017-10-01
A central challenge in modern condensed matter physics is developing the tools for understanding nontrivial yet unordered states of matter. One important idea to emerge in this context is that of a ‘pseudogap’: the fact that under appropriate circumstances the normal state displays a suppression of the single particle spectral density near the Fermi level, reminiscent of the gaps seen in ordered states of matter. While these concepts arose in a solid state context, they are now being explored in cold gases. This article reviews the current experimental and theoretical understanding of the normal state of strongly interacting Fermi gases, with particular focus on the phenomonology which is traditionally associated with the pseudogap.
Wang, Yayu; Li, Lu; Naughton, M J; Gu, G D; Uchida, S; Ong, N P
2005-12-09
In hole-doped cuprates, Nernst experiments imply that the superconducting state is destroyed by spontaneous creation of vortices which destroy phase coherence. Using torque magnetometry on Bi2Sr2CaCu2O(8+delta), we uncover a field-enhanced diamagnetic signal M above the transition temperature Tc that increases with applied field to 32 Tesla and scales just like the Nernst signal. The magnetization results above Tc distinguish M from conventional amplitude fluctuations and strongly support the vortex scenario for the loss of phase coherence at Tc.
Ground states of linearly coupled Schrodinger systems
Directory of Open Access Journals (Sweden)
Haidong Liu
2017-01-01
Full Text Available This article concerns the standing waves of a linearly coupled Schrodinger system which arises from nonlinear optics and condensed matter physics. The coefficients of the system are spatially dependent and have a mixed behavior: they are periodic in some directions and tend to positive constants in other directions. Under suitable assumptions, we prove that the system has a positive ground state. In addition, when the L-infinity-norm of the coupling coefficient tends to zero, the asymptotic behavior of the ground states is also obtained.
Trapped Antihydrogen in Its Ground State
Gabrielse, G.; Kolthammer, W.S.; McConnell, R.; Richerme, P.; Grzonka, D.; Oelert, W.; Sefzick, T.; Zielinski, M.; Fitzakerley, D.W.; George, M.C.; Hessels, E.A.; Storry, C.H.; Weel, M.; Müllers, A.; Walz, J.
2012-03-16
Antihydrogen atoms are confined in an Ioffe trap for 15 to 1000 seconds -- long enough to ensure that they reach their ground state. Though reproducibility challenges remain in making large numbers of cold antiprotons and positrons interact, 5 +/- 1 simultaneously-confined ground state atoms are produced and observed on average, substantially more than previously reported. Increases in the number of simultaneously trapped antithydrogen atoms H are critical if laser-cooling of trapped antihydrogen is to be demonstrated, and spectroscopic studies at interesting levels of precision are to be carried out.
Quantum Ground States as Equilibrium Particle-Vacuum Interaction States
Puthoff, Harold E
2012-01-01
A remarkable feature of atomic ground states is that they are observed to be radiationless in nature, despite (from a classical viewpoint) typically involving charged particles in accelerated motions. The simple hydrogen atom is a case in point. This universal groundstate characteristic is shown to derive from particle-vacuum interactions in which a dynamic equilibrium is established between radiation emission due to particle acceleration, and compensatory absorption from the zero-point fluctuations of the vacuum electromagnetic field. The result is a net radiationless ground state. This principle constitutes an overarching constraint that delineates an important feature of quantum ground states.
A model of evaluating the pseudogap temperature for high ...
Indian Academy of Sciences (India)
We have presented a model of evaluating the pseudogap temperature for high temperature superconductors using paraconductivity approach. The theoretical analysis is based on the crossing point technique of the conductivity expressions. The pseudogap temperature T ∗ is found to depend on dimension and is ...
Thermodynamic Ground States of Complex Oxide Heterointerfaces
DEFF Research Database (Denmark)
Gunkel, F.; Hoffmann-Eifert, S.; Heinen, R. A.
2017-01-01
The formation mechanism of 2-dimensional electron gases (2DEGs) at heterointerfaces between nominally insulating oxides is addressed with a thermodynamical approach. We provide a comprehensive analysis of the thermodynamic ground states of various 2DEG systems directly probed in high temperature...
Rearrangements in ground and excited states
de Mayo, Paul
1980-01-01
Rearrangements in Ground and Excited States, Volume 3 presents essays on the chemical generation of excited states; the cis-trans isomerization of olefins; and the photochemical rearrangements in trienes. The book also includes essays on the zimmerman rearrangements; the photochemical rearrangements of enones; the photochemical rearrangements of conjugated cyclic dienones; and the rearrangements of the benzene ring. Essays on the photo rearrangements via biradicals of simple carbonyl compounds; the photochemical rearrangements involving three-membered rings or five-membered ring heterocycles;
Storey, J. G.
2017-10-01
High-temperature superconducting cuprates are distinguished by an enigmatic pseudogap which opens near optimal doping where the superconducting transition temperature is highest. Key questions concern its origin and whether it is essential in any way to superconductivity. Recent field-induced normal-state transport experiments on hole-doped cuprates have measured abrupt changes in the doping-dependent Hall number and resistivity, consistent with a drop in carrier density from 1+p to p holes per copper atom, on entering the pseudogap phase. In this work the change in resistivity is analyzed in terms of an antiferromagnetic-order-induced Fermi surface reconstruction model that has already successfully described the Hall number. In order for this model to describe the resistivity we find that the zero-temperature mean free path must also drop abruptly in proportion to the size of the Fermi surface. This suggests that intrapocket scattering underlies the observed upturn in resistivity in the pseudogap state.
Weak Pseudogap Behavior in the Underdoped Cuprate Superconductors
Energy Technology Data Exchange (ETDEWEB)
Schmalian, J.; Pines, D. [University of Illinois at Urbana-Champaign, Loomis Laboratory of Physics, 1110 W. Green, Urbana, Illinois 61801 (United States); Pines, D.; Stojkovic, B. [Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
1998-04-01
We report on a novel solution of the nearly antiferromagnetic (AF) spin fermion model in the limit {pi}T{gt}{omega}{sub sf} , which demonstrates that the broad high energy features found in angular resolved photoemission spectroscopy measurements of the spectral density of the underdoped cuprates are determined by strong (AF) correlations and precursor effects of a spin density wave state. We show that the onset temperature, T{sup cr} , of weak pseudogap behavior is determined by the strength, {xi} , of the (AF) correlations, and obtain the generic changes in low frequency magnetic behavior seen in NMR experiments with {xi}(T{sup cr}){approx}2 , confirming the Barzykin and Pines crossover criterion. {copyright} {ital 1998} {ital The American Physical Society}
Trapping cold ground state argon atoms.
Edmunds, P D; Barker, P F
2014-10-31
We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable 4s[3/2](2) state to be (7.3±1.1)×10(-39) C m(2)/V. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be (3.3±0.8)×10(-10) cm(3) s(-1).
Electronic ground state of Ni$_2^+$
Zamudio-Bayer, V; Bülow, C; Leistner, G; Terasaki, A; Issendorff, B v; Lau, J T
2016-01-01
The $^{4}\\Phi_{9/2}$ ground state of the Ni$_2^+$ diatomic molecular cation is determined experimentally from temperature and magnetic-field-dependent x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap, where an electronic and rotational temperature of $7.4 \\pm 0.2$ K was achieved by buffer gas cooling of the molecular ion. The contribution of the magnetic dipole term to the x-ray magnetic circular dichroism spin sum rule amounts to $7\\, T_z = 0.17 \\pm 0.06$ $\\mu_B$ per atom, approximately 11 \\% of the spin magnetic moment. We find that, in general, homonuclear diatomic molecular cations of $3d$ transition metals seem to adopt maximum spin magnetic moments in their electronic ground states.
Rearrangements in ground and excited states
de Mayo, Paul
1980-01-01
Rearrangements in Ground and Excited States, Volume 2 covers essays on the theoretical approach of rearrangements; the rearrangements involving boron; and the molecular rearrangements of organosilicon compounds. The book also includes essays on the polytopal rearrangement at phosphorus; the rearrangement in coordination complexes; and the reversible thermal intramolecular rearrangements of metal carbonyls. Chemists and people involved in the study of rearrangements will find the book invaluable.
Numerical Evaluation of 2D Ground States
Directory of Open Access Journals (Sweden)
Kolkovska Natalia
2016-01-01
The efficiency of this procedure is demonstrated in the 1D case, where the maximal difference between the exact and numerical solution is ≈ 10–11 for a discretization step 0:00025. As a major application, we evaluate numerically the critical energy constant. This constant is defined as a functional of the ground state and is used in the study of the 2D Boussinesq equations.
DEFF Research Database (Denmark)
Severin, Gregory; Knutson, L. D.; Voytas, P. A.
2014-01-01
The ground state branch of the β decay of 66Ga is an allowed Fermi (0+ → 0+) transition with a relatively high f t value. The large f t and the isospin-forbidden nature of the transition indicates that the shape of the β spectrum of this branch may be sensitive to higher order contributions...... to the decay. Two previous measurements of the shape have revealed deviations from an allowed spectrum but disagree about whether the shape factor has a positive or negative slope. As a test of a new iron-free superconducting β spectrometer, we have measured the shape of the ground state branch of the 66Ga β...... spectrum above a positron energy of 1.9 MeV. The spectrum is consistent with an allowed shape, with the slope of the shape factor being zero to within ±3 × 10−3 per MeV. We have also determined the endpoint energy for the ground state branch to be 4.1535 ± 0.0003 (stat.) ±0.0007 (syst.) MeV, in good...
Encoding Universal Computation in the Ground States of Ising Lattices
Gu, Mile; Perales, Alvaro
2012-01-01
We characterize the set of ground states that can be synthesized by classical 2-body Ising Hamiltonians. We then construct simple Ising planar blocks that simulates efficiently a universal set of logic gates and connections, and hence any boolean function. We therefore provide a new method of encoding universal computation in the ground states of Ising lattices, and a simpler alternative demonstration of the known fact that finding the ground state of a finite Ising spin glass model is NP com...
Universality of pseudogap and emergent order in lightly doped Mott insulators
Battisti, I.; Bastiaans, K. M.; Fedoseev, V.; de la Torre, A.; Iliopoulos, N.; Tamai, A.; Hunter, E. C.; Perry, R. S.; Zaanen, J.; Baumberger, F.; Allan, M. P.
2017-01-01
It is widely believed that high-temperature superconductivity in the cuprates emerges from doped Mott insulators. When extra carriers are inserted into the parent state, the electrons become mobile but the strong correlations from the Mott state are thought to survive--inhomogeneous electronic order, a mysterious pseudogap and, eventually, superconductivity appear. How the insertion of dopant atoms drives this evolution is not known, nor is whether these phenomena are mere distractions specific to hole-doped cuprates or represent genuine physics of doped Mott insulators. Here we visualize the evolution of the electronic states of (Sr1-xLax)2IrO4, which is an effective spin-1/2 Mott insulator like the cuprates, but is chemically radically different. Using spectroscopic-imaging scanning tunnelling microscopy (SI-STM), we find that for a doping concentration of x ~ 5%, an inhomogeneous, phase-separated state emerges, with the nucleation of pseudogap puddles around clusters of dopant atoms. Within these puddles, we observe the same iconic electronic order that is seen in underdoped cuprates. We investigate the genesis of this state and find evidence at low doping for deeply trapped carriers, leading to fully gapped spectra, which abruptly collapse at a threshold of x ~ 4%. Our results clarify the melting of the Mott state, and establish phase separation and electronic order as generic features of doped Mott insulators.
Triaxiality of the ground states in the 174W
Directory of Open Access Journals (Sweden)
Ya Tu
2016-01-01
Full Text Available We have performed calculations for the ground states in 174W by using the projected total energy surface (PTES calculations. Both the ground state (g.s. band and its γ band reproduce the experimental data. Further discussion about the triaxiality in 174W has been made by transition quardrupole moment (Qt and comparing between the PTES and TRS methods.
Triaxiality of the ground states in the 174W
Ya, Tu; Chen, Y. S.; Liu, L.; Gao, Z. C.
2016-05-01
We have performed calculations for the ground states in 174W by using the projected total energy surface (PTES) calculations. Both the ground state (g.s.) band and its γ band reproduce the experimental data. Further discussion about the triaxiality in 174W has been made by transition quardrupole moment (Qt) and comparing between the PTES and TRS methods.
A model of evaluating the pseudogap temperature for high ...
Indian Academy of Sciences (India)
DOI: 10.1007/s12043-015-1088-3; ePublication: 30 September 2015. Abstract. We have presented a model of evaluating the pseudogap temperature for high- temperature superconductors using paraconductivity approach. The theoretical analysis is based on the crossing point technique of the conductivity expressions.
Classical many-particle systems with unique disordered ground states.
Zhang, G; Stillinger, F H; Torquato, S
2017-10-01
Classical ground states (global energy-minimizing configurations) of many-particle systems are typically unique crystalline structures, implying zero enumeration entropy of distinct patterns (aside from trivial symmetry operations). By contrast, the few previously known disordered classical ground states of many-particle systems are all high-entropy (highly degenerate) states. Here we show computationally that our recently proposed "perfect-glass" many-particle model [Sci. Rep. 6, 36963 (2016)10.1038/srep36963] possesses disordered classical ground states with a zero entropy: a highly counterintuitive situation . For all of the system sizes, parameters, and space dimensions that we have numerically investigated, the disordered ground states are unique such that they can always be superposed onto each other or their mirror image. At low energies, the density of states obtained from simulations matches those calculated from the harmonic approximation near a single ground state, further confirming ground-state uniqueness. Our discovery provides singular examples in which entropy and disorder are at odds with one another. The zero-entropy ground states provide a unique perspective on the celebrated Kauzmann-entropy crisis in which the extrapolated entropy of a supercooled liquid drops below that of the crystal. We expect that our disordered unique patterns to be of value in fields beyond glass physics, including applications in cryptography as pseudorandom functions with tunable computational complexity.
Simple variational ground state and pure-cat-state generation in the quantum Rabi model
Leroux, C.; Govia, L. C. G.; Clerk, A. A.
2017-10-01
We introduce a simple, physically motivated variational ground state for the quantum Rabi model and demonstrate that it provides a high-fidelity approximation of the true ground state in all parameter regimes (including intermediate- and strong-coupling regimes). Our variational state is constructed using Gaussian cavity states and nonorthogonal qubit pointer states and contains only three variational parameters. We use our state to develop a heuristic understanding of how the ground state evolves with increasing coupling and find a parameter regime where the ground state corresponds to the cavity being in a nearly pure Schrödinger cat state.
Entanglement of two ground state neutral atoms using Rydberg blockade
DEFF Research Database (Denmark)
Miroshnychenko, Yevhen; Browaeys, Antoine; Evellin, Charles
2011-01-01
We report on our recent progress in trapping and manipulation of internal states of single neutral rubidium atoms in optical tweezers. We demonstrate the creation of an entangled state between two ground state atoms trapped in separate tweezers using the effect of Rydberg blockade. The quality...... of the entanglement is measured using global rotations of the internal states of both atoms....
Encoding universal computation in the ground states of Ising lattices
Gu, Mile; Perales, Álvaro
2012-07-01
We characterize the set of ground states that can be synthesized by classical two-body Ising Hamiltonians. We then construct simple Ising planar blocks that simulate efficiently a universal set of logic gates and connections, and hence any Boolean function. We therefore provide a new method of encoding universal computation in the ground states of Ising lattices and a simpler alternative demonstration of the known fact that finding the ground state of a finite Ising spin glass model is NP complete. We relate this with our previous result about emergent properties in infinite lattices.
Encoding universal computation in the ground states of Ising lattices.
Gu, Mile; Perales, Álvaro
2012-07-01
We characterize the set of ground states that can be synthesized by classical two-body Ising Hamiltonians. We then construct simple Ising planar blocks that simulate efficiently a universal set of logic gates and connections, and hence any Boolean function. We therefore provide a new method of encoding universal computation in the ground states of Ising lattices and a simpler alternative demonstration of the known fact that finding the ground state of a finite Ising spin glass model is NP complete. We relate this with our previous result about emergent properties in infinite lattices.
Classical ground states of symmetric Heisenberg spin systems
Schmidt, H J
2003-01-01
We investigate the ground states of classical Heisenberg spin systems which have point group symmetry. Examples are the regular polygons (spin rings) and the seven quasi-regular polyhedra including the five Platonic solids. For these examples, ground states with special properties, e.g. coplanarity or symmetry, can be completely enumerated using group-theoretical methods. For systems having coplanar (anti-) ground states with vanishing total spin we also calculate the smallest and largest energies of all states having a given total spin S. We find that these extremal energies depend quadratically on S and prove that, under certain assumptions, this happens only for systems with coplanar S = 0 ground states. For general systems the corresponding parabolas represent lower and upper bounds for the energy values. This provides strong support and clarifies the conditions for the so-called rotational band structure hypothesis which has been numerically established for many quantum spin systems.
Adiabatic ground state preparation in an expanding lattice
Gazit, Snir; Olund, Chris; Yao, Norman
2017-04-01
We numerically investigate the newly proposed s-source framework for constructing ground state wave functions of gapped Hamiltonians. The key idea is to utilize the adiabatic principle to build a tensor network representation that smoothly interpolates between the ground state of system sizes L and 2L via an interleaved set of ancillary degrees of freedom. Repeatedly applying this procedure reproduces the thermodynamic limit. The scheme should be contrasted with conventional tensor network methods that rely on the variational principle to target the ground state by iteratively improving a variational energy. We introduce a simple yet flexible tensor network structure and an optimization protocol borrowing techniques from quantum control theory. We anticipate that this approach can, in principle, allow access to problems beyond current tensor network technology and even serve as an experimental scheme for ground state preparation in quantum engineered systems.
Arsenic in Ground Water of the United States - Direct Download
U.S. Geological Survey, Department of the Interior — This image shows national-scale patterns of naturally occurring arsenic in potable ground-water resources of the continental United States. The image was generated...
Theory of ground state factorization in quantum cooperative systems.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2008-05-16
We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows us to determine rigorously the existence, location, and exact form of separable ground states in a large variety of, generally nonexactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective of spatial dimensionality, and for spin-spin interactions of arbitrary range.
Probing quantum frustrated systems via factorization of the ground state.
Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio
2010-05-21
The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures.
Path Integrals for the Projection of the Electronic Ground State
Esler, K. P.; Romero, N. A.; Ceperley, D. M.
2001-06-01
Diffusion Monte Carlo (DMC) has been used for the high-accuracy study of the ground state properties of large electronic systems for many years. Despite its many successes, DMC has major shortcomings (eg. mixed estimators, time step errors). We present an evaluation of an alternative ground state Monte Carlo method, based on path integrals, which addresses some of these shortcomings. In particular, we provide a brief description of the ground state path integral (GSPIMC) method and compare its scaling behavior, efficiencies, and deficiencies with those of DMC. We provide results from a number of test calculations on molecular systems. We attempt to provide insight into the circumstances under which it is preferable to utilize each algorithm.
Ground state entanglement and geometric entropy in the Kitaev model
Energy Technology Data Exchange (ETDEWEB)
Hamma, Alioscia [Institute for Scientific Interchange (ISI), Villa Gualino, Viale Settimio Severo 65, I-10133 Turin (Italy); Dipartimento di Scienze Fisiche, Universita Federico II, Via Cintia ed. G, I-80126 Napoli (Italy); Ionicioiu, Radu [Institute for Scientific Interchange (ISI), Villa Gualino, Viale Settimio Severo 65, I-10133 Turin (Italy); Zanardi, Paolo [Institute for Scientific Interchange (ISI), Villa Gualino, Viale Settimio Severo 65, I-10133 Turin (Italy)]. E-mail: zanardi@isiosf.isi.it
2005-03-28
We study the entanglement properties of the ground state in Kitaev's model. This is a two-dimensional spin system with a torus topology and non-trivial four-body interactions between its spins. For a generic partition (A,B) of the lattice we calculate analytically the von Neumann entropy of the reduced density matrix {rho}{sub A} in the ground state. We prove that the geometric entropy associated with a region A is linear in the length of its boundary. Moreover, we argue that entanglement can probe the topology of the system and reveal topological order. Finally, no partition has zero entanglement and we find the partition that maximizes the entanglement in the given ground state.
Cluster emission in superdeformed Sr isotopes in the ground state ...
Indian Academy of Sciences (India)
2017-01-03
Jan 3, 2017 ... Abstract. Cluster decay of superdeformed 76,78,80Sr isotopes in their ground state are studied taking the Coulomb and proximity potential as the interacting barrier for the post-scission region. The predicted T1/2 values are found to be in close agreement with those values reported by the preformed cluster ...
Numerical calculation of the ground state of Helium atom using ...
African Journals Online (AJOL)
Hylleraas did the calculation of the ground state in 1926 using the variational parameter a. In this paper we trace Hylleraas historic calculation, the use of computer enables us to improve the approximation found by Hylleraas . The program was written in FORTRAN language, designed in such away that for a particular value ...
Advantages of Unfair Quantum Ground-State Sampling.
Zhang, Brian Hu; Wagenbreth, Gene; Martin-Mayor, Victor; Hen, Itay
2017-04-21
The debate around the potential superiority of quantum annealers over their classical counterparts has been ongoing since the inception of the field. Recent technological breakthroughs, which have led to the manufacture of experimental prototypes of quantum annealing optimizers with sizes approaching the practical regime, have reignited this discussion. However, the demonstration of quantum annealing speedups remains to this day an elusive albeit coveted goal. We examine the power of quantum annealers to provide a different type of quantum enhancement of practical relevance, namely, their ability to serve as useful samplers from the ground-state manifolds of combinatorial optimization problems. We study, both numerically by simulating stoquastic and non-stoquastic quantum annealing processes, and experimentally, using a prototypical quantum annealing processor, the ability of quantum annealers to sample the ground-states of spin glasses differently than thermal samplers. We demonstrate that (i) quantum annealers sample the ground-state manifolds of spin glasses very differently than thermal optimizers (ii) the nature of the quantum fluctuations driving the annealing process has a decisive effect on the final distribution, and (iii) the experimental quantum annealer samples ground-state manifolds significantly differently than thermal and ideal quantum annealers. We illustrate how quantum annealers may serve as powerful tools when complementing standard sampling algorithms.
Ground State Energy of Current Carriers in Graphene
Ratnikov, P. V.; Silin, A. P.
2008-01-01
The ground state energy of current carriers in graphene considered as a zero-gap semiconductor was calculated in the two-band approximation. The condition of the electronic (hole) system stability in graphene was obtained. The possibility of the zero-gap semiconductor-semimetal transition was discussed.
Hartree–Fock variational bounds for ground state energy of ...
Indian Academy of Sciences (India)
The existence of a stable equilibrium high density ferromagnetic state with spheroidal occupation function is possible as long as the ratio of coupling constants Γcm ≡ (U0a3/μ2) is not very small compared to 1. Keywords. Chargeless fermions; magnetic dipole–dipole interaction; Hartree–Fock bounds; ferromagnetic ground ...
Magnetic excitons in singlet-ground-state ferromagnets
DEFF Research Database (Denmark)
Birgeneau, R.J.; Als-Nielsen, Jens Aage; Bucher, E.
1971-01-01
The authors report measurements of the dispersion of singlet-triplet magnetic excitons as a function of temperature in the singlet-ground-state ferromagnets fcc Pr and Pr3Tl. Well-defined excitons are observed in both the ferromagnetic and paramagnetic regions, but with energies which are nearly...
Ground state structures and properties of small hydrogenated silicon ...
Indian Academy of Sciences (India)
We present results for ground state structures and properties of small hydrogenated silicon clusters using the Car–Parrinello molecular dynamics with simulated annealing. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen can form a bridge like Si–H–Si bond connecting two silicon ...
Ground state structures and properties of small hydrogenated silicon ...
Indian Academy of Sciences (India)
Unknown
Abstract. We present results for ground state structures and properties of small hydrogenated silicon clus- ters using the Car–Parrinello molecular dynamics with simulated annealing. We discuss the nature of bonding of hydrogen in these clusters. We find that hydrogen can form a bridge like Si–H–Si bond connecting two ...
Hartree–Fock variational bounds for ground state energy of ...
Indian Academy of Sciences (India)
We use different determinantal Hartree–Fock (HF) wave functions to calculate true variational upper bounds for the ground state energy of spin-half fermions in volume 0, with mass , electric charge zero, and magnetic moment , interacting through magnetic dipole–dipole interaction. We ﬁnd that at high densities ...
Quantum dimer model for the pseudogap metal.
Punk, Matthias; Allais, Andrea; Sachdev, Subir
2015-08-04
We propose a quantum dimer model for the metallic state of the hole-doped cuprates at low hole density, p. The Hilbert space is spanned by spinless, neutral, bosonic dimers and spin S = 1/2, charge +e fermionic dimers. The model realizes a "fractionalized Fermi liquid" with no symmetry breaking and small hole pocket Fermi surfaces enclosing a total area determined by p. Exact diagonalization, on lattices of sizes up to 8 × 8, shows anisotropic quasiparticle residue around the pocket Fermi surfaces. We discuss the relationship to experiments.
Quantum quenches in the thermodynamic limit. II. Initial ground states
Rigol, Marcos
2014-09-01
A numerical linked-cluster algorithm was recently introduced to study quantum quenches in the thermodynamic limit starting from thermal initial states [M. Rigol, Phys. Rev. Lett. 112, 170601 (2014), 10.1103/PhysRevLett.112.170601]. Here, we tailor that algorithm to quenches starting from ground states. In particular, we study quenches from the ground state of the antiferromagnetic Ising model to the XXZ chain. Our results for spin correlations are shown to be in excellent agreement with recent analytical calculations based on the quench action method. We also show that they are different from the correlations in thermal equilibrium, which confirms the expectation that thermalization does not occur in general in integrable models even if they cannot be mapped to noninteracting ones.
Producing translationally cold, ground-state CO molecules
Blokland, Janneke H; Putzke, Stephan; Sartakov, Boris G; Groenenboom, Gerrit C; Meijer, Gerard; 10.1063/1.3637037
2011-01-01
Carbon monoxide molecules in their electronic, vibrational, and rotational ground state are highly attractive for trapping experiments. The optical or ac electric traps that can be envisioned for these molecules will be very shallow, however, with depths in the sub-milliKelvin range. Here we outline that the required samples of translationally cold CO (X$^1\\Sigma^+$, $v"$=0, $N"$=0) molecules can be produced after Stark deceleration of a beam of laser-prepared metastable CO (a$^3\\Pi_1$) molecules followed by optical transfer of the metastable species to the ground state \\emph{via} perturbed levels in the A$^1\\Pi$ state. The optical transfer scheme is experimentally demonstrated and the radiative lifetimes and the electric dipole moments of the intermediate levels are determined.
Superconducting fluctuations and pseudogap in high-Tc cuprates
Directory of Open Access Journals (Sweden)
Alloul H.
2012-03-01
Full Text Available Large pulsed magnetic fields up to 60 Tesla are used to suppress the contribution of superconducting fluctuations (SCF to the ab-plane conductivity above Tc in a series of YBa2Cu3O6+x. These experiments allow us to determine the field Hc’(T and the temperature Tc’ above which the SCFs are fully suppressed. A careful investigation near optimal doping shows that Tc’ is higher than the pseudogap temperature T*, which is an unambiguous evidence that the pseudogap cannot be assigned to preformed pairs. Accurate determinations of the SCF contribution to the conductivity versus temperature and magnetic field have been achieved. They can be accounted for by thermal fluctuations following the Ginzburg-Landau scheme for nearly optimally doped samples. A phase fluctuation contribution might be invoked for the most underdoped samples in a T range which increases when controlled disorder is introduced by electron irradiation. Quantitative analysis of the fluctuating magnetoconductance allows us to determine the critical field Hc2(0 which is found to be be quite similar to Hc’ (0 and to increase with hole doping. Studies of the incidence of disorder on both Tc’ and T* allow us to to propose a three dimensional phase diagram including a disorder axis, which allows to explain most observations done in other cuprate families.
Mixed configuration ground state in iron(II) phthalocyanine
Energy Technology Data Exchange (ETDEWEB)
Fernández-Rodríguez, Javier; Toby, Brian; van Veenendaal, Michel
2015-06-01
We calculate the angular dependence of the x-ray linear and circular dichroism at the L2,3 edges of α-Fe(II) Phthalocyanine (FePc) thin films using a ligand-field model with full configuration interaction. We find the best agreement with the experimental spectra for a mixed ground state of 3E (a2 e3b1 ) and 3B (a1 e4b1 ) g 1g g 2g 2g 1g g 2g with the two configurations coupled by the spin-orbit interaction. The 3Eg(b) and 3B2g states have easy-axis and easy-plane anisotropies, respectively. Our model accounts for an easy-plane magnetic anisotropy and the measured magnitudes of the in-plane orbital and spin moments. The proximity in energy of the two configurations allows a switching of the magnetic anisotropy from easy plane to easy axis with a small change in the crystal field, as recently observed for FePc adsorbed on an oxidized Cu surface. We also discuss the possibility of a quintet ground state (5A1g is 250 meV above the ground state) with planar anisotropy by manipulation of the Fe-C bond length by depositing the complex on a substrate that is subjected to a mechanical strain.
Guidelines for ground motion definition for the eastern United States
Energy Technology Data Exchange (ETDEWEB)
Gwaltney, R.C.; Aramayo, G.A.; Williams, R.T.
1985-06-01
Guidelines for the determination of earthquake ground motion definition for the eastern United States are established here. Both far-field and near-field guidelines are given. The guidelines were based on an extensive review of the current procedures for specifying ground motion in the United States. Both empirical and theoretical procedures were used in establishing the guidelines because of the low seismicity in the eastern United States. Only a few large- to great-sized earthquakes (M/sub s/ > 7.5) have occurred in this region, no evidence of tectonic surface ruptures related to historic or Holocene earthquakes has been found, and no currently active plate boundaries of any kind are known in this region. Very little instrumented data have been gathered in the East. Theoretical procedures are proposed so that in regions of almost no data, a reasonable level of seismic ground motion activity can be assumed. The guidelines are to be used to develop the safe shutdown earthquake (SSE). A new procedure for establishing the operating basis earthquake (OBE) is proposed, in particular for the eastern United States. The OBE would be developed using a probabilistic assessment of the geological conditions and the recurrence of seismic events at a site. These guidelines should be useful in development of seismic design requirements for future reactors. 17 refs., figs., tabs.
New Measurement of the 5H Ground State
McNeel, Daniel G.; Wuosmaa, A. H.; Bedoor, S.; Newton, A. S.; Brown, K. W.; Charity, R. J.; Sobotka, L. G.; Buhro, W. W.; Chajecki, Z.; Lynch, W. G.; Manfredi, J.; Showalter, R. H.; Tsang, M. B.; Winklebauer, J. R.; Marley, S. T.; Shetty, D. V.
2015-10-01
We have studied the ground state of 5H using the 6He(d,3He)5H reaction in inverse kinematics. Existing data for 5H are in conflict with each other and with many theoretical predictions. This measurement provides a clear evidence for the 5H ground state, and the previously unreported 6He(d,t)5Heg.s. reaction is also observed. A 6He beam at 55 MeV/A produced at the National Superconducting Cyclotron Laboratory at Michigan State University bombarded a 1.9 mg/cm2 (CD2)n target. The reaction products were detected with HiRA (the High Resolution Array). The 3He and 3H particles from the 6He(d,3He/3H)5H/5He reactions were detected in coincidence with the decay products of the unstable 5H and 5He nuclei, providing signatures for the transitions of interest. The properties of the 5He ground state provide information about the calibration and response of the apparatus. Details of the measurement, and a comparison of the data with earlier results and theoretical calculations, will be presented. Work supported by the U.S. Department of Energy under Contracts DE-FG02-04ER41320 and DE-FG02-87ER40316, and the U. S. National Science Foundation under Grant Numbers PHY-1068217 and PHY-1068192.
Energy Technology Data Exchange (ETDEWEB)
Pieri, P.; Perali, A.; Strinati, G. C. [Dipartimento di Fisica, Universita di Camerino, I-62032 Camerino (Italy); Riedl, S.; Altmeyer, A.; Grimm, R. [Institut fuer Experimentalphysik und Zentrum fuer Quantenphysik, Universitaet Innsbruck, A-6020 Innsbruck (Austria); Institut fuer Quantenoptik und Quanteninformation, Oesterreichische Akademie der Wissenschaften, A-6020 Innsbruck (Austria); Wright, M. J.; Kohstall, C.; Sanchez Guajardo, E. R.; Hecker Denschlag, J. [Institut fuer Experimentalphysik und Zentrum fuer Quantenphysik, Universitaet Innsbruck, A-6020 Innsbruck (Austria)
2011-07-15
Radio frequency spectra of a trapped unitary {sup 6}Li gas are reported and analyzed in terms of a theoretical approach that includes both final-state and trap effects. The different strength of the final-state interaction across the trap is crucial for evidencing two main peaks associated with two distinct phases residing in different trap regions. These are the pairing-gap and pseudo-gap phases below the critical temperature T{sub c}, which evolve into the pseudo-gap and no-gap phases above T{sub c}. In this way, a long standing puzzle about the interpretation of rf spectra for {sup 6}Li in a trap is solved.
Monte Carlo Ground State Energy for Trapped Boson Systems
Rudd, Ethan; Mehta, N. P.
2012-06-01
Diffusion Monte Carlo (DMC) and Green's Function Monte Carlo (GFMC) algorithms were implemented to obtain numerical approximations for the ground state energies of systems of bosons in a harmonic trap potential. Gaussian pairwise particle interactions of the form V0e^-|ri-rj|^2/r0^2 were implemented in the DMC code. These results were verified for small values of V0 via a first-order perturbation theory approximation for which the N-particle matrix element evaluated to N2 V0(1 + 1/r0^2)^3/2. By obtaining the scattering length from the 2-body potential in the perturbative regime (V0φ 1), ground state energy results were compared to modern renormalized models by P.R. Johnson et. al, New J. Phys. 11, 093022 (2009).
Ground-state structures of atomic metallic hydrogen.
McMahon, Jeffrey M; Ceperley, David M
2011-04-22
Ab initio random structure searching using density functional theory is used to determine the ground-state structures of atomic metallic hydrogen from 500 GPa to 5 TPa. Including proton zero-point motion within the harmonic approximation, we estimate that molecular hydrogen dissociates into a monatomic body-centered tetragonal structure near 500 GPa (r(s)=1.23) that remains stable to 1 TPa (r(s)=1.11). At higher pressures, hydrogen stabilizes in an …ABCABC… planar structure that is similar to the ground state of lithium, but with a different stacking sequence. With increasing pressure, this structure compresses to the face-centered cubic lattice near 3.5 TPa (r(s)=0.92).
Room temperature skyrmion ground state stabilized through interlayer exchange coupling
Energy Technology Data Exchange (ETDEWEB)
Chen, Gong, E-mail: gchenncem@gmail.com; Schmid, Andreas K. [NCEM, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Mascaraque, Arantzazu [Depto. Física de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Unidad Asociada IQFR (CSIC) - UCM, 28040 Madrid (Spain); N' Diaye, Alpha T. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2015-06-15
Possible magnetic skyrmion device applications motivate the search for structures that extend the stability of skyrmion spin textures to ambient temperature. Here, we demonstrate an experimental approach to stabilize a room temperature skyrmion ground state in chiral magnetic films via exchange coupling across non-magnetic spacer layers. Using spin polarized low-energy electron microscopy to measure all three Cartesian components of the magnetization vector, we image the spin textures in Fe/Ni films. We show how tuning the thickness of a copper spacer layer between chiral Fe/Ni films and perpendicularly magnetized Ni layers permits stabilization of a chiral stripe phase, a skyrmion phase, and a single domain phase. This strategy to stabilize skyrmion ground states can be extended to other magnetic thin film systems and may be useful for designing skyrmion based spintronics devices.
Cluster expansion for ground states of local Hamiltonians
Directory of Open Access Journals (Sweden)
Alvise Bastianello
2016-08-01
Full Text Available A central problem in many-body quantum physics is the determination of the ground state of a thermodynamically large physical system. We construct a cluster expansion for ground states of local Hamiltonians, which naturally incorporates physical requirements inherited by locality as conditions on its cluster amplitudes. Applying a diagrammatic technique we derive the relation of these amplitudes to thermodynamic quantities and local observables. Moreover we derive a set of functional equations that determine the cluster amplitudes for a general Hamiltonian, verify the consistency with perturbation theory and discuss non-perturbative approaches. Lastly we verify the persistence of locality features of the cluster expansion under unitary evolution with a local Hamiltonian and provide applications to out-of-equilibrium problems: a simplified proof of equilibration to the GGE and a cumulant expansion for the statistics of work, for an interacting-to-free quantum quench.
Ground state solutions for diffusion system with superlinear nonlinearity
Directory of Open Access Journals (Sweden)
Zhiming Luo
2015-03-01
where $z=(u,v\\colon\\mathbb{R}\\times\\mathbb{R}^{N}\\rightarrow\\mathbb{R}^{2}$, $b\\in C^{1}(\\mathbb{R}\\times\\mathbb{R}^{N}, \\mathbb{R}^{N}$ and $V(x\\in C(\\mathbb{R}^{N},\\mathbb{R}$. Under suitable assumptions on the nonlinearity, we establish the existence of ground state solutions by the generalized Nehari manifold method developed recently by Szulkin and Weth.
Ground state solutions for non-local fractional Schrodinger equations
Directory of Open Access Journals (Sweden)
Yang Pu
2015-08-01
Full Text Available In this article, we study a time-independent fractional Schrodinger equation with non-local (regional diffusion $$ (-\\Delta^{\\alpha}_{\\rho}u + V(xu = f(x,u \\quad \\text{in }\\mathbb{R}^{N}, $$ where $\\alpha \\in (0,1$, $N > 2\\alpha$. We establish the existence of a non-negative ground state solution by variational methods.
Available energy and ground states of collisionless plasmas
Helander, Per
2017-08-01
The energy budget of a collisionless plasma subject to electrostatic fluctuations is considered, and the excess of thermal energy over the minimum accessible to it under various constraints that limit the possible forms of plasma motion is calculated. This excess measures how much thermal energy is `available' for conversion into plasma instabilities, and therefore constitutes a nonlinear measure of plasma stability. A distribution function with zero available energy defines a `ground state' in the sense that its energy cannot decrease by any linear or nonlinear plasma motion. In a Vlasov plasma with small density and temperature fluctuations, the available energy is proportional to the mean square of these quantities, and exceeds the corresponding energy in ideal or resistive magnetohydrodynamics. If the first or second adiabatic invariant is conserved, ground states generally have inhomogeneous density and temperature. Magnetically confined plasmas are usually not in any ground state, but certain types of stellarator plasmas are so with respect to fluctuations that conserve both these adiabatic invariants, making the plasma linearly and nonlinearly stable to such fluctuations. Similar stability properties can also be enjoyed by plasmas confined by a dipole magnetic field.
Two different ground states in K-doped polyacenes
Heguri, Satoshi; Phan Thi Nhu, Quynh; Tamura, Hiroyuki; Nakano, Takehito; Nozue, Yasuo; Tanigaki, Katsumi; AIMR Team; Department of Physics Team; Osaka University Team
The electronic states of potassium (K) doped zigzag-type polycyclic aromatic hydrocarbon (polyacenes (PLAs)) Kx(PLAs), are studied for a series of the four smallest molecules: naphthalene (NN), anthrance (AN), tetracene (TN), and pentacene (PN), focusing on their 1:1 stoichiometric phases. Clear experimental differences are identified between the first group (K1(NN) and K1(AN)) and the second group (K1(TN) and K1(PN)) by magnetic, vibrational, and optical measurements. The first group is categorized as a Mott insulator with an antiferromagnetic ground state with energy of c.a. 10 meV, while the second group is classified as a band insulator via dimer formation due to the spin Peierls instability. In the latter system, the first thermally accessible triplet states are located far apart from the singlet ground states at room temperature, and are not detected by electron spin resonance spectroscopy until 300 K, being very different from what is observed for hole doped PN reported earlier. The results give a new systematic understanding on the electronic states of electron doped PLAs sensitive to the energetic balance among on-site Coulomb repulsion, band width and the Peierls instability.
Boson-fermion mixture model of superconductivity and pseudogap phenomena
Energy Technology Data Exchange (ETDEWEB)
Mamedov, Tofik
2004-08-01
A concept describing the origin of the pseudogap phase of high-T{sub c}-superconducting cuprates is discussed. Based on the idea about electron-composite boson mixture, existing below some value T{sub p} in cuprates, first, an analytical expression for T{sub p} is obtained. It is shown that T{sub p} depends on interaction parameter responsible for two electron-composite boson transformation, as well on the boson formation energy. Second, the composite boson condensation temperature T{sub c}, determined as a one below which the density of condensed bosons just ceases to be zero, is found. The reason why the behaviors of T{sub p} and T{sub c} in dependence on the interaction parameter may be so different is addressed.
Klf4 reverts developmentally programmed restriction of ground state pluripotency.
Guo, Ge; Yang, Jian; Nichols, Jennifer; Hall, John Simon; Eyres, Isobel; Mansfield, William; Smith, Austin
2009-04-01
Mouse embryonic stem (ES) cells derived from pluripotent early epiblast contribute functionally differentiated progeny to all foetal lineages of chimaeras. By contrast, epistem cell (EpiSC) lines from post-implantation epithelialised epiblast are unable to colonise the embryo even though they express the core pluripotency genes Oct4, Sox2 and Nanog. We examined interconversion between these two cell types. ES cells can readily become EpiSCs in response to growth factor cues. By contrast, EpiSCs do not change into ES cells. We exploited PiggyBac transposition to introduce a single reprogramming factor, Klf4, into EpiSCs. No effect was apparent in EpiSC culture conditions, but in ground state ES cell conditions a fraction of cells formed undifferentiated colonies. These EpiSC-derived induced pluripotent stem (Epi-iPS) cells activated expression of ES cell-specific transcripts including endogenous Klf4, and downregulated markers of lineage specification. X chromosome silencing in female cells, a feature of the EpiSC state, was erased in Epi-iPS cells. They produced high-contribution chimaeras that yielded germline transmission. These properties were maintained after Cre-mediated deletion of the Klf4 transgene, formally demonstrating complete and stable reprogramming of developmental phenotype. Thus, re-expression of Klf4 in an appropriate environment can regenerate the naïve ground state from EpiSCs. Reprogramming is dependent on suppression of extrinsic growth factor stimuli and proceeds to completion in less than 1% of cells. This substantiates the argument that EpiSCs are developmentally, epigenetically and functionally differentiated from ES cells. However, because a single transgene is the minimum requirement to attain the ground state, EpiSCs offer an attractive opportunity for screening for unknown components of the reprogramming process.
Estimating the ground-state probability of a quantum simulation with product-state measurements
Directory of Open Access Journals (Sweden)
Bryce eYoshimura
2015-10-01
Full Text Available .One of the goals in quantum simulation is to adiabatically generate the ground state of a complicated Hamiltonian by starting with the ground state of a simple Hamiltonian and slowly evolving the system to the complicated one. If the evolution is adiabatic and the initial and final ground states are connected due to having the same symmetry, then the simulation will be successful. But in most experiments, adiabatic simulation is not possible because it would take too long, and the system has some level of diabatic excitation. In this work, we quantify the extent of the diabatic excitation even if we do not know {it a priori} what the complicated ground state is. Since many quantum simulator platforms, like trapped ions, can measure the probabilities to be in a product state, we describe techniques that can employ these simple measurements to estimate the probability of being in the ground state of the system after the diabatic evolution. These techniques do not require one to know any properties about the Hamiltonian itself, nor to calculate its eigenstate properties. All the information is derived by analyzing the product-state measurements as functions of time.
Ground state instabilities of protein shells are eliminated by buckling.
Singh, Amit R; Perotti, Luigi E; Bruinsma, Robijn F; Rudnick, Joseph; Klug, William S
2017-11-15
We propose a hybrid discrete-continuum model to study the ground state of protein shells. The model allows for shape transformation of the shell and buckling transitions as well as the competition between states with different symmetries that characterize discrete particle models with radial pair potentials. Our main results are as follows. For large Föppl-von Kármán (FvK) numbers the shells have stable isometric ground states. As the FvK number is reduced, shells undergo a buckling transition resembling that of thin-shell elasticity theory. When the width of the pair potential is reduced below a critical value, then buckling coincides with the onset of structural instability triggered by over-stretched pair potentials. Chiral shells are found to be more prone to structural instability than achiral shells. It is argued that the well-width appropriate for protein shells lies below the structural instability threshold. This means that the self-assembly of protein shells with a well-defined, stable structure is possible only if the bending energy of the shell is sufficiently low so that the FvK number of the assembled shell is above the buckling threshold.
Triaxiality near the 110Ru ground state from Coulomb excitation
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D.T. Doherty
2017-03-01
Full Text Available A multi-step Coulomb excitation measurement with the GRETINA and CHICO2 detector arrays was carried out with a 430-MeV beam of the neutron-rich 110Ru (t1/2=12 s isotope produced at the CARIBU facility. This represents the first successful measurement following the post-acceleration of an unstable isotope of a refractory element. The reduced transition probabilities obtained for levels near the ground state provide strong evidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxial rotor model calculations.
First observation of ground state dineutron decay: 16Be.
Spyrou, A; Kohley, Z; Baumann, T; Bazin, D; Brown, B A; Christian, G; DeYoung, P A; Finck, J E; Frank, N; Lunderberg, E; Mosby, S; Peters, W A; Schiller, A; Smith, J K; Snyder, J; Strongman, M J; Thoennessen, M; Volya, A
2012-03-09
We report on the first observation of dineutron emission in the decay of 16Be. A single-proton knockout reaction from a 53 MeV/u 17B beam was used to populate the ground state of 16Be. 16Be is bound with respect to the emission of one neutron and unbound to two-neutron emission. The dineutron character of the decay is evidenced by a small emission angle between the two neutrons. The two-neutron separation energy of 16Be was measured to be 1.35(10) MeV, in good agreement with shell model calculations, using standard interactions for this mass region.
Absence of Energy Level Crossing for the Ground State Energy of the Rabi Model
Hirokawa, Masao; Hiroshima, Fumio
2012-01-01
The Hamiltonian of the Rabi model is considered. It is shown that the ground state energy of the Rabi Hamiltonian is simple for all values of the coupling strength, which implies the ground state energy does not cross other energy
Directory of Open Access Journals (Sweden)
Alejandro Cabo Montes de Oca
2010-03-01
Full Text Available This work expands the results and derivations presented in a recent letter. It is argued that symmetry breaking Hartree-Fock (HF solutions of a simple model of the Cu-O planes in La2CuO4, are able to describe the insulator and antiferromagnetic characters of this material. Then, this classical primer of a Mott insulator is alternatively obtained here as an exact Slater insulator within the simplest of the first principles schemes. Moreover, pseudogap HF states are also predicted. The maximal energy gap of 100 meV over the Fermi surface of this wavefunction, reasonably well matches the ARPES upper pseudogap measurements for La2CuO4 in the zero doping limit. These surprising results followed after eliminating spin and crystal symmetry constraints usually imposed on the HF orbitals. The discussion helps to clarify the role of the antiferromagnetism and pseudogaps in the physics of the HTSC materials and indicates a promising way to start conciliating the Mott and Slater pictures for the description of the transition metal oxides.
Ground-state electronic structure of actinide monocarbides and mononitrides
DEFF Research Database (Denmark)
Petit, Leon; Svane, Axel; Szotek, Z.
2009-01-01
The self-interaction corrected local spin-density approximation is used to investigate the ground-state valency configuration of the actinide ions in the actinide monocarbides, AC (A=U,Np,Pu,Am,Cm), and the actinide mononitrides, AN. The electronic structure is characterized by a gradually...... to the localization transition. The calculated valence electron densities of states are in good agreement with photoemission data....... increasing degree of f electron localization from U to Cm, with the tendency toward localization being slightly stronger in the (more ionic) nitrides compared to the (more covalent) carbides. The itinerant band picture is found to be adequate for UC and acceptable for UN, while a more complex manifold...
First evidence for a virtual {sup 18}B ground state
Energy Technology Data Exchange (ETDEWEB)
Spyrou, A., E-mail: spyrou@nscl.msu.ed [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Baumann, T.; Bazin, D. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Blanchon, G. [CEA, DAM, DIF F-91297 Arpajon (France); Bonaccorso, A. [Istituto Nazionale di Fisica Nucleare, Sez. di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Breitbach, E. [Department of Physics, Marquette University, Milwaukee, WI 53201 (United States); Brown, J. [Department of Physics, Wabash College, Crawfordsville, IN 47933 (United States); Christian, G. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); DeLine, A. [Department of Physics, Central Michigan University, Mt. Pleasant, MI 48859 (United States); DeYoung, P.A. [Department of Physics, Hope College, Holland, MI 49423 (United States); Finck, J.E. [Department of Physics, Central Michigan University, Mt. Pleasant, MI 48859 (United States); Frank, N. [Department of Physics and Astronomy, Augustana College, Rock Island, IL 61201 (United States); Mosby, S. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Peters, W.A. [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States); Russel, A. [Department of Physics, Central Michigan University, Mt. Pleasant, MI 48859 (United States); Schiller, A. [Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States)
2010-01-18
The decay of the neutron unbound ground state of {sup 18}B was studied for the first time through a single-proton knockout reaction from a 62 MeV/u {sup 19}C beam. The decay energy spectrum was reconstructed from coincidence measurements between the emitted neutron and the {sup 17}B fragment using the MoNA/Sweeper setup. An s-wave line shape was used to describe the experimental spectrum resulting in an upper limit for the scattering length of -50 fm which corresponds to a decay energy <10 keV. Observing an s-wave decay of {sup 18}B provides an experimental verification that the ground state of {sup 19}C includes a large s-wave component. The presence of this s-wave component shows that s-d mixing is still present in {sup 18}B and that the s{sub 1/2} orbital has not moved significantly below the d{sub 5/2} orbital.
Quantum renormalization group for ground-state fidelity
Langari, A.; Rezakhani, A. T.
2012-05-01
Ground-state fidelity (GSF) and quantum renormalization group (QRG) theory have proven to be useful tools in the study of quantum critical systems. Here we lay out a general, unified formalism of GSF and QRG; specifically, we propose a method for calculating GSF through QRG, obviating the need for calculating or approximating ground states. This method thus enhances the characterization of quantum criticality as well as scaling analysis of relevant properties with system size. We illustrate the formalism in the one-dimensional Ising model in a transverse field (ITF) and the anisotropic spin-1/2 Heisenberg (XXZ) model. Explicitly, we find the scaling behavior of the GSF for the ITF model in both small- and large-size limits, the corresponding critical exponents, the exact value of the GSF in the thermodynamic limit and a closed form for the GSF for arbitrary size and system parameters. In the case of the XXZ model, we also present an analytic expression for the GSF, which captures well the criticality of the model, hence excluding doubts that GSF might be an insufficient tool for signaling criticality in this model.
Ground state configurations in antiferromagnetic ultrathin films with dipolar anisotropy
Energy Technology Data Exchange (ETDEWEB)
Leon, H., E-mail: hleon@imre.oc.uh.cu [Instituto de Ciencia y Tecnologia de Materiales, Universidad de La Habana, Zapata e/ Mazon y G. Vedado, 10400 La Habana (Cuba)
2013-02-15
The formalism developed in a previous work to calculate the dipolar energy in quasi-two-dimensional crystals with ferromagnetic order is now extended to collinear antiferromagnetic order. Numerical calculations of the dipolar energy are carried out for systems with tetragonally distorted fcc [001] structures, the case of NiO and MnO ultrathin film grown in non-magnetic substrates, where the magnetic phase is a consequence of superexchange and dipolar interactions. The employed approximation allows to demonstrate that dipolar coupling between atomic layers is responsible for the orientation of the magnetization when it differs from the one in a single layer. The ground state energy of a given NiO or MnO film is found to depend not only on the strain, but also on how much the interlayer separation and the 2D lattice constant are changed with respect to the ideal values corresponding to the non-distorted cubic structure. Nevertheless, it is shown that the orientation of the magnetization in the magnetic phase of any of these films is determined by the strain exclusively. A striped phase with the magnetization along the [112{sup Macron }] direction appears as the ground state configuration of NiO and MnO ultrathin films. In films with equally oriented stripes along the layers this magnetic phase is twofold degenerate, while in films with multidomain layers it is eightfold degenerate. These results are not in contradiction with experimentally observed out-of-plane or in-plane magnetization of striped phases in NiO and MnO ultrathin films. - Highlights: Black-Right-Pointing-Pointer Dipolar energy in collinear antiferromagnetic ultrathin films is calculated. Black-Right-Pointing-Pointer Numerical results are presented for distorted fcc [001] structures. Black-Right-Pointing-Pointer The lowest energy of a system depends on how the tetragonal distortion is achieved. Black-Right-Pointing-Pointer A striped phase with magnetization in the [112{sup Macron }] direction is the
Ground-state level spin systems within Bernasconi model
Leukhin, A. N.; Bezrodnyi, V. I.; Voronin, A. A.; Kokovikhina, N. A.
2017-10-01
The design problem for law autocorrelation binary sequences (LABS) is a notoriously difficult computational problem which is numbered as the problem number 005 in CSPLib. In statistical physics LABS problem can be interpreted as the energy of N interacting Ising spins. This is a Bernasconi model for a one N-dimensional chain of quantum particles. Ground-state level quantum system within the frame of Bernasconi model is binary sequence with lowest level of peak-sidelobes of aperiodic autocorrelation function. The new results of an exhaustive search for optimal binary sequences with minimum peak sidelobe up to length N=86 are demonstrated. The Bernasconi model exhibits features of a glass transition like a jump in the specific heat and slow dynamics and aging. The Bernasconi model the high temperature phase of Ising spin system reproduces exactly approximation.
Unresolved question of the 10He ground state resonance.
Kohley, Z; Snyder, J; Baumann, T; Christian, G; DeYoung, P A; Finck, J E; Haring-Kaye, R A; Jones, M; Lunderberg, E; Luther, B; Mosby, S; Simon, A; Smith, J K; Spyrou, A; Stephenson, S L; Thoennessen, M
2012-12-07
The ground state of (10)He was populated using a 2p2n-removal reaction from a 59 MeV/u (14)Be beam. The decay energy of the three-body system, (8)He+n+n, was measured and a resonance was observed at E=1.60(25) MeV with a 1.8(4) MeV width. This result is in agreement with previous invariant mass spectroscopy measurements, using the (11)Li(-p) reaction, but is inconsistent with recent transfer reaction results. The proposed explanation that the difference, about 500 keV, is due to the effect of the extended halo nature of (11)Li in the one-proton knockout reaction is no longer valid as the present work demonstrates that the discrepancy between the transfer reaction results persists despite using a very different reaction mechanism, (14)Be(-2p2n).
Ground-state properties of neutron magic nuclei
Energy Technology Data Exchange (ETDEWEB)
Saxena, G., E-mail: gauravphy@gmail.com [Govt. Women Engineering College, Department of Physics (India); Kaushik, M. [Shankara Institute of Technology, Department of Physics (India)
2017-03-15
A systematic study of the ground-state properties of the entire chains of even–even neutron magic nuclei represented by isotones of traditional neutron magic numbers N = 8, 20, 40, 50, 82, and 126 has been carried out using relativistic mean-field plus Bardeen–Cooper–Schrieffer approach. Our present investigation includes deformation, binding energy, two-proton separation energy, single-particle energy, rms radii along with proton and neutron density profiles, etc. Several of these results are compared with the results calculated using nonrelativistic approach (Skyrme–Hartree–Fock method) along with available experimental data and indeed they are found with excellent agreement. In addition, the possible locations of the proton and neutron drip-lines, the (Z, N) values for the new shell closures, disappearance of traditional shell closures as suggested by the detailed analyzes of results are also discussed in detail.
Ground-state correlations within a nonperturbative approach
De Gregorio, G.; Herko, J.; Knapp, F.; Lo Iudice, N.; Veselý, P.
2017-02-01
The contribution of the two-phonon configurations to the ground state of 4He and 16O is evaluated nonperturbatively using a Hartree-Fock basis within an equation-of-motion phonon method using a nucleon-nucleon optimized chiral potential. Convergence properties of energies and root-mean-square radii versus the harmonic oscillator frequency and space dimensions are investigated. The comparison with the second-order perturbation theory calculations shows that the higher-order terms have an appreciable repulsive effect and yield too-small binding energies and nuclear radii. It is argued that four-phonon configurations, through their strong coupling to two phonons, may provide most of the attractive contribution necessary for filling the gap between theoretical and experimental quantities. Possible strategies for accomplishing such a challenging task are discussed.
Ground State Properties of a Homogeneous Bose-Einstein Condensate
Smith, Robert; Gotlibovych, Igor; Schmidutz, Tobias; Gaunt, Alex; Navon, Nir; Hadzibabic, Zoran
2014-05-01
We will present measurements of the coherence, energy and free expansion of a quasi-homogeneous atomic Bose-Einstein condensate (BEC) in an optical box potential. We have measured the ground state wave function of a trapped quasi-pure BEC in momentum space using Bragg spectroscopy and compare this with the real-space wave function. We find excellent quantitative agreement with the Heisenberg uncertainty principle and also confirm the expected scaling of the momentum uncertainty with the box length. In addition, by varying the condensate atom number, we have studied the effect of interactions on the momentum distribution and mean-field energy of the condensate. Finally, we will present measurements of the evolution in time of both the mean-field energy and the momentum distribution of a freely expanding condensate.
DEFF Research Database (Denmark)
Reynisson, J.; Wilbrandt, R.; Brinck, V.
2002-01-01
of the long wavelength absorption band. A strong fluorescence is observed at 520 nm (tau(n) = 14.6 ns, phi(n) = 0.12 in deaerated acetonitrile). The fluorescence is quenched by 10 aromatic electron donors predominantly via a dynamic charge transfer mechanism, but ground state complexation is shown...
State estimators for tracking sharply-maneuvering ground targets
Visina, Radu S.; Bar-Shalom, Yaakov; Willett, Peter
2017-05-01
This paper presents an algorithm, based on the Interacting Multiple Model Estimator, that can be used to track the state of kinematic point targets, moving in two dimensions, that are capable of making sharp heading maneuvers over short periods of time, such as certain ground vehicles moving in an open field. The targets are capable of up to 60 °/s turn rates, while polar measurements are received at 1 Hz. We introduce the Non-Zero Mean, White Noise Turn-Rate IMM (IMM-WNTR) that consists of 3 modes based on a White Noise Turn Rate (WNTR) kinematic model that contains additive, white, Gaussian turn rate process noises. Two of the modes are considered maneuvering modes, and they have opposite (left/right), non-zero mean turn rate input noise. The need for non-zero mean turn rate process noise is explained, and Monte Carlo simulations compare this novel design to the traditional (single-mode) White Noise Acceleration Kalman Filter (WNA KF) and the two-mode White Noise Acceleration/Nearly-Coordinated Turn Rate IMM (IMM-CT). Results show that the IMM-WNTR filter achieves better accuracy and real-time consistency between expected error and actual error as compared to the (single-mode) WNA KF and the IMM-CT in all simulated scenarios, making it a very accurate state estimator for targets with sharp coordinated turn capability in 2D.
Quantum algorithm for preparing the ground state of a system via resonance transition.
Wang, Hefeng
2017-11-27
Preparing the ground state of a system is an important task in physics. We propose a quantum algorithm for preparing the ground state of a physical system that can be simulated on a quantum computer. The system is coupled to an ancillary qubit, by introducing a resonance mechanism between the ancilla qubit and the system, and combined with measurements performed on the ancilla qubit, the system can be evolved to monotonically converge to its ground state through an iterative procedure. We have simulated the application of this algorithm for the Afflect-Kennedy-Lieb-Tasaki model, whose ground state can be used as resource state in one-way quantum computation.
Insights into Ultrafast Demagnetization in Pseudogap Half-Metals
Directory of Open Access Journals (Sweden)
Andreas Mann
2012-11-01
Full Text Available Interest in femtosecond demagnetization dynamics was sparked by Bigot’s experiment in 1996, which unveiled the elementary mechanisms that relate the electrons’ temperature to their spin order. Simultaneously, the application of fast demagnetization experiments has been demonstrated to provide key insight into technologically important systems such as high-spin-polarization metals, and consequently there is broad interest in further understanding the physics of these phenomena. To gain new and relevant insights, we performed ultrafast optical pump-probe experiments to characterize the demagnetization processes of highly spin-polarized magnetic thin films on a femtosecond time scale. Full spin polarization is obtained in half-metallic ferro- or ferrimagnets, where only one spin channel is populated at the Fermi level, whereas the other one exhibits a gap. In these materials, the spin-scattering processes is controlled via the electronic structure, and thus their ultrafast demagnetization is solely related to the spin polarization via a Fermi golden-rule model. Accordingly, a long demagnetization time correlates with a high spin polarization due to the suppression of the spin-flip scattering at around the Fermi level. Here we show that isoelectronic Heusler compounds (Co_{2}MnSi, Co_{2}MnGe, and Co_{2}FeAl exhibit a degree of spin polarization between 59% and 86%. We explain this behavior by considering the robustness of the gap against structural disorder. Moreover, we observe that CoFe-based pseudogap materials, such as partially ordered Co-Fe-Ge and Co-Fe-B alloys, can reach similar values of the spin polarization. By using the unique features of these metals we vary the number of possible spin-flip channels, which allows us to pinpoint and control the half-metals’ electronic structure and its influence on the elementary mechanisms of ultrafast demagnetization.
First determination of ground state electromagnetic moments of 53Fe
Miller, A. J.; Minamisono, K.; Rossi, D. M.; Beerwerth, R.; Brown, B. A.; Fritzsche, S.; Garand, D.; Klose, A.; Liu, Y.; Maaß, B.; Mantica, P. F.; Müller, P.; Nörtershäuser, W.; Pearson, M. R.; Sumithrarachchi, C.
2017-11-01
The hyperfine coupling constants of neutron deficient 53Fe were deduced from the atomic hyperfine spectrum of the 3 d64 s25D4↔3 d64 s 4 p 5F5 transition, measured using the bunched-beam collinear laser spectroscopy technique. The low-energy 53Fe beam was produced by projectile-fragmentation reactions followed by gas stopping, and used for the first time for laser spectroscopy. Ground state magnetic-dipole and electric-quadrupole moments were determined as μ =-0.65 (1 ) μN and Q =+35 (15 ) e2fm2 , respectively. The multiconfiguration Dirac-Fock method was used to calculate the electric field gradient to deduce Q from the quadrupole hyperfine coupling constant, since the quadrupole coupling constant has not been determined for any Fe isotopes. Both experimental values agree well with nuclear shell model calculations using the GXPF1A effective interaction performed in a full f p shell model space, which support the soft nature of the 56Ni nucleus.
On the DFT ground state of crystalline bromine and iodine.
George, Janine; Reimann, Christoph; Deringer, Volker L; Bredow, Thomas; Dronskowski, Richard
2015-03-16
We report on an erroneous ground state within common density functional theory (DFT) methods for the solid elements bromine and iodine. Phonon computations at the GGA level for both molecular crystals yield imaginary vibrational modes, erroneously indicating dynamic instability-that fact alone could easily pass as a computational artefact, but these imaginary modes lead to energetically more favorable and dynamically stable structures, made up of infinite monoatomic chains. In contrast, meta-GGA and hybrid functionals yield the correct energetic order for bromine, while for iodine, most global hybrids do not improve the GGA result significantly. The qualitatively correct answer, in both cases, is given by the long-range corrected hybrid LC-ωPBE, the Minnesota functionals M06L and M06, and by periodic Hartree-Fock and MP2 theory. This poor performance of economic DFT functionals should be kept in mind, for example, during global structure optimizations of systems with significant contributions from halogen bonds. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Schmidt, A. R.; Fujita, K.; Kim, E.-A.; Lawler, M. J.; Eisaki, H.; Uchida, S.; Lee, D.-H.; Davis, J. C.
2011-06-01
We survey the use of spectroscopic imaging scanning tunneling microscopy (SI-STM) to probe the electronic structure of underdoped cuprates. Two distinct classes of electronic states are observed in both the d-wave superconducting (dSC) and the pseudogap (PG) phases. The first class consists of the dispersive Bogoliubov quasiparticle excitations of a homogeneous d-wave superconductor, existing below a lower energy scale E=Δ0. We find that the Bogoliubov quasiparticle interference (QPI) signatures of delocalized Cooper pairing are restricted to a k-space arc, which terminates near the lines connecting k=±(π/a0,0) to k=±(0,π/a0). This arc shrinks continuously with decreasing hole density such that Luttinger's theorem could be satisfied if it represents the front side of a hole-pocket that is bounded behind by the lines between k=±(π/a0,0) and k=±(0,π/a0). In both phases, the only broken symmetries detected for the |E|translational symmetries, coexist with this intra-unit-cell electronic symmetry breaking at E=Δ1. Their characteristic wavevector Q is determined by the k-space points where Bogoliubov QPI terminates and therefore changes continuously with doping. The distinct broken electronic symmetry states (intra-unit-cell and finite Q) coexisting at E~Δ1 are found to be indistinguishable in the dSC and PG phases. The next challenge for SI-STM studies is to determine the relationship of the E~Δ1 broken symmetry electronic states with the PG phase, and with the E<Δ0 states associated with Cooper pairing.
Upper Bounds on the Degeneracy of the Ground State in Quantum Field Models
Directory of Open Access Journals (Sweden)
Asao Arai
2016-01-01
Full Text Available Axiomatic abstract formulations are presented to derive upper bounds on the degeneracy of the ground state in quantum field models including massless ones. In particular, given is a sufficient condition under which the degeneracy of the ground state of the perturbed Hamiltonian is less than or equal to the degeneracy of the ground state of the unperturbed one. Applications of the abstract theory to models in quantum field theory are outlined.
Ground-State Analysis for an Exactly Solvable Coupled-Spin Hamiltonian
Directory of Open Access Journals (Sweden)
Eduardo Mattei
2013-11-01
Full Text Available We introduce a Hamiltonian for two interacting su(2 spins. We use a mean-field analysis and exact Bethe ansatz results to investigate the ground-state properties of the system in the classical limit, defined as the limit of infinite spin (or highest weight. Complementary insights are provided through investigation of the energy gap, ground-state fidelity, and ground-state entanglement, which are numerically computed for particular parameter values. Despite the simplicity of the model, a rich array of ground-state features are uncovered. Finally, we discuss how this model may be seen as an analogue of the exactly solvable p+ip pairing Hamiltonian.
Ground state solutions for asymptotically periodic Schrodinger equations with critical growth
Directory of Open Access Journals (Sweden)
Hui Zhang
2013-10-01
Full Text Available Using the Nehari manifold and the concentration compactness principle, we study the existence of ground state solutions for asymptotically periodic Schrodinger equations with critical growth.
Energy Technology Data Exchange (ETDEWEB)
Schmalian, J. [University of Illinois at Urbana-Champaign, Loomis Laboratory of Physics, 1110 West Green Street, Urbana, Illinois 61801 (United States); Pines, D. [University of Illinois at Urbana-Champaign, Loomis Laboratory of Physics, 1110 West Green Street, Urbana, Illinois 61801 (United States)]|[Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Stojkovic, B. [Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
1999-07-01
We use a solution of the spin fermion model which is valid in the quasistatic limit {pi}T{gt}{omega}{sub sf}, found in the intermediate (pseudoscaling) regime of the magnetic phase diagram of cuprate superconductors, to obtain results for the temperature and doping dependence of the single particle spectral density, the electron-spin fluctuation vertex function, and the low frequency dynamical spin susceptibility. The resulting strong anisotropy of the spectral density and the vertex function lead to the qualitatively different behavior of {ital hot} [around {bold k}=({pi},0)] and {ital cold} [around {bold k}=({pi}/2,{pi}/2)] quasiparticles seen in ARPES experiments. We find that the broad high energy features found in ARPES measurements of the spectral density of the underdoped cuprate superconductors are determined by strong antiferromagnetic (AF) correlations and incoherent precursor effects of an SDW state, with reduced renormalized effective coupling constant. Due to this transfer of spectral weight to higher energies, the low frequency spectral weight of {ital hot} states is strongly reduced but couples very strongly to the spin excitations of the system. For realistic values of the antiferromagnetic correlation length, their Fermi surface changes its general shape only slightly but the strong scattering of hot states makes the Fermi surface crossing invisible above a pseudogap temperature T{sub {asterisk}}. The electron spin-fluctuation vertex function, i.e., the effective interaction of low energy quasiparticles and spin degrees of freedom, is found to be strongly anisotropic and enhanced for hot quasiparticles; the corresponding charge-fluctuation vertex is considerably diminished. We thus demonstrate that, once established, strong AF correlations act to reduce substantially the effective electron-phonon coupling constant in cuprate superconductors. {copyright} {ital 1999} {ital The American Physical Society}
E2 transitions between excited single-phonon states: Role of ground-state correlations
Energy Technology Data Exchange (ETDEWEB)
Kamerdzhiev, S. P. [National Research Centre Kurchatov Institute (Russian Federation); Voitenkov, D. A., E-mail: dvoytenkov@ippe.ru [Institute for Physics and Power Engineering (Russian Federation)
2016-11-15
The probabilities for E2 transitions between low-lying excited 3{sup −} and 5{sup −} single-phonon states in the {sup 208}Pb and {sup 132}Sn magic nuclei are estimated on the basis of the theory of finite Fermi systems. The approach used involves a new type of ground-state correlations, that which originates from integration of three (rather than two, as in the random-phase approximation) single-particle Green’s functions. These correlations are shown to make a significant contribution to the probabilities for the aforementioned transitions.
Tricriticality for dimeric Coulomb molecular crystals in ground state
Travěnec, Igor; Šamaj, Ladislav
2017-12-01
We study the ground-state properties of a system of dimers. Each dimer consists in a pair of equivalent charges at a fixed distance, immersed in a neutralizing homogeneous background. All charges interact pairwisely by Coulomb potential. The dimer centers form a two-dimensional rectangular lattice with the aspect ratio α\\in [0, 1] and each dimer is allowed to rotate around its center. The previous numerical simulations, made for the more general Yukawa interaction, indicate that only two basic dimer configurations can appear: either all dimers are parallel or they have two different angle orientations within alternating (checkerboard) sublattices. As the dimer size increases, two second-order phase transitions, related to two kinds of the symmetry breaking in dimer’s orientations, were reported. In this paper, we use a recent analytic method based on an expansion of the interaction energy in Misra functions which converges quickly and provides an analytic derivation of the critical behaviour. Our main result is that there exists a specific aspect ratio of the rectangular lattice α^*=0.714 106 840 000 71\\ldots which divides the space of model’s phases onto two distinct regions. If the lattice aspect ratio α>α* , we recover both types of the second-order phase transitions and find that they are of mean-field type with the critical exponent β = 1/2 . If 0.711 535≤slantα<α* , the phase transition associated with the discontinuity of dimer’s angles on alternating sublattices becomes of first order. For α=α* , the first- and second-order phase transitions meet at the tricritical point, characterized by the different critical index β = 1/4 . Such phenomenon is known from literature about the Landau theory of one-component fields, but in our two-component version the scenario is more complicated: the component which is already in the symmetry-broken state at the tricritical point also interferes and exhibits unexpectedly the mean-field singular
Cluster decay of Ba isotopes from ground state and as an excited ...
Indian Academy of Sciences (India)
122 is studied by modifying the Coulomb and proximity potential model for both the ground and excited state decays ... 20 and they arise as multiple clusters and are accompanied by multiple light particles. (Z ≤ 2). ... all aspects of α and cluster decay from these isotopes from both ground and excited states beginning with ...
Relativistic and correlated calculations on the ground, excited, and ionized states of iodine
de Jong, W.A.; Visscher, L; Nieuwpoort, W.C
1997-01-01
The electronic structure, spectroscopic, and bonding properties of the ground, excited, and ionized states of iodine are studied within a four-component relativistic framework using the MOLFDIR program package, The experimentally determined properties of the (1) Sigma(g)(+) ground state are well
No-go theorem for ground state cooling given initial system-thermal bath factorization.
Wu, Lian-Ao; Segal, Dvira; Brumer, Paul
2013-01-01
Ground-state cooling and pure state preparation of a small object that is embedded in a thermal environment is an important challenge and a highly desirable quantum technology. This paper proves, with two different methods, that a fundamental constraint on the cooling dynamic implies that it is impossible to cool, via a unitary system-bath quantum evolution, a system that is embedded in a thermal environment down to its ground state, if the initial state is a factorized product of system and bath states. The latter is a crucial but artificial assumption included in numerous tools that treat system-bath dynamics, such as master equation approaches and Kraus operator based methods. Adopting these approaches to address ground state and even approximate ground state cooling dynamics should therefore be done with caution, considering the fundamental theorem exposed in this work.
The significant role of covalency in determining the ground state of cobalt phthalocyanines molecule
Directory of Open Access Journals (Sweden)
Jing Zhou
2016-03-01
Full Text Available To shed some light on the metal 3d ground state configuration of cobalt phthalocyanines system, so far in debate, we present an investigation by X-ray absorption spectroscopy (XAS at Co L2,3 edge and theoretical calculation. The density functional theory calculations reveal highly anisotropic covalent bond between central cobalt ion and nitrogen ligands, with the dominant σ donor accompanied by weak π-back acceptor interaction. Our combined experimental and theoretical study on the Co-L2,3 XAS spectra demonstrate a robust ground state of 2A1g symmetry that is built from 73% 3d7 character and 27% 3 d 8 L ¯ ( L ¯ denotes a ligand hole components, as the first excited-state with 2Eg symmetry lies about 158 meV higher in energy. The effect of anisotropic and isotropic covalency on the ground state was also calculated and the results indicate that the ground state with 2A1g symmetry is robust in a large range of anisotropic covalent strength while a transition of ground state from 2A1g to 2Eg configuration when isotropic covalent strength increases to a certain extent. Here, we address a significant anisotropic covalent effect of short Co(II-N bond on the ground state and suggest that it should be taken into account in determining the ground state of analogous cobalt complexes.
Ground states of anisotropic antiferromagnets with single ion and cubic anisotropy
Directory of Open Access Journals (Sweden)
T.-C. Dinh
2009-01-01
Full Text Available Anisotropic antiferromagnets in an external magnetic field show a rich variety of different ground states meeting in transition lines and multicritical points. We study the dependence of the ground states of these systems in the three dimensional space on physical parameters such as exchange, single ion and cubic anisotropy. One identifies four different ground states: the paramagnetic (PM, the antiferromagnetic (AF, the spin flop (SF and the biconical (BC ground state. In the case of absence of a cubic anisotropy, the transition lines separating different ground states can be calculated analytically, otherwise they have to be calculated numerically. We also considered the behavior of the staggered magnetization which characterizes the different ground states. From its behavior the order of the transition from one state to the other is determined. But also the order of the transition changes along the transition lines when including the cubic anisotropy, especially at the reeentrant region where a transition from SF to BC and back to SF by increasing the external field H occurs. Multicritical points are found which are assumed to be tricritical or critical endpoints. The results obtained may be relevant for other systems since the antiferromagnetic model can be mapped to a lattice gas model where the biconical ground state is interpreted as supersolid phase. Recent renormalization group calculations show that such a phase would indicate the existence of a tetracritical point.
Three Order Parameters in Quantum XZ Spin-Oscillator Models with Gibbsian Ground States
Directory of Open Access Journals (Sweden)
Wolodymyr I. Skrypnik
2008-01-01
Full Text Available Quantum models on the hyper-cubic d-dimensional lattice of spin-1/2 particles interacting with linear oscillators are shown to have three ferromagnetic ground state order parameters. Two order parameters coincide with the magnetization in the first and third directions and the third one is a magnetization in a continuous oscillator variable. The proofs use a generalized Peierls argument and two Griffiths inequalities. The class of spin-oscillator Hamiltonians considered manifest maximal ordering in their ground states. The models have relevance for hydrogen-bond ferroelectrics. The simplest of these is proven to have a unique Gibbsian ground state.
Evaluation of ground water quality of Mubi town in Adamawa State ...
African Journals Online (AJOL)
The ground water quality of Mubi Town in Mubi North Local Government Area of Adamawa State was studied to examine the suitability or otherwise of their use of the groundwater for drinking and domestic purposes. Ten ground water samples from boreholes and dug wells were randomly collected each during raining ...
Pseudogap and proximity effect in the Bi2Te3/Fe1+yTe interfacial superconductor.
He, M Q; Shen, J Y; Petrović, A P; He, Q L; Liu, H C; Zheng, Y; Wong, C H; Chen, Q H; Wang, J N; Law, K T; Sou, I K; Lortz, R
2016-09-02
In the interfacial superconductor Bi2Te3/Fe1+yTe, two dimensional superconductivity occurs in direct vicinity to the surface state of a topological insulator. If this state were to become involved in superconductivity, under certain conditions a topological superconducting state could be formed, which is of high interest due to the possibility of creating Majorana fermionic states. We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface. Our data show highly unconventional superconductivity, which appears as complex as in the cuprate high temperature superconductors. A very large superconducting twin-gap structure is replaced by a pseudogap above ~12 K which persists up to 40 K. While the larger gap shows unconventional order parameter symmetry and is attributed to a thin FeTe layer in proximity to the interface, the smaller gap is associated with superconductivity induced via the proximity effect in the topological insulator Bi2Te3.
Mott-like behavior in the pseudogap region of the Hubbard model
Galanakis, Dimitrios; Mikelsons, Karlis; Khatami, Ehsan; Jarrell, Mark; Macridin, Alexandru; Ma, Michael; Moreno, Juana
2009-03-01
We study the phase diagram of the two-dimensional Hubbard model using the Dynamical Cluster Approximation (DCA) in conjunction with the weak-coupling continuous time quantum Monte Carlo (CTQMC) as the cluster solver. We verify the existence of a quantum critical point at a finite electron doping which separates a fermi liquid region at low electron doping from the pseudogap region at high electron doping ootnotetextVidhyadhiraja et. al., arXiv:0809.1477v1. In the pseudogap region the double occupancy, the two particle correlation functions and spectra reveal a synergism between the development of moment formation and the appearance of short ranged order. We discuss the connection between our results and experiments.
Pseudogaps and Their Interplay with Magnetic Excitations in the Doped 2D Hubbard Model
Energy Technology Data Exchange (ETDEWEB)
Preuss, R.; Hanke, W.; Groeber, C.; Evertz, H.G. [Institut fuer Theoretische Physik, Am Hubland, D-97074 Wuerzburg (Germany)
1997-08-01
On the basis of quantum Monte Carlo simulations of the two-dimensional Hubbard model which cover the doping range from the underdoped to the overdoped regime, we find that the single-particle spectral weight A({rvec k},{omega}) qualitatively reproduces both the momentum (d{sub x{sup 2}{minus}y{sup 2}} symmetry) and doping dependence of the pseudogap as found in photoemission experiments. The drastic doping dependence of the spin response {chi}{sub s}({rvec q},{omega}), which is sharp in both {rvec q}[{approx}({pi},{pi})] and {omega} in the underdoped regime but broad and structureless otherwise, identifies remnants of the antiferromagnetic order as the driving mechanism behind the pseudogap and its evolution with doping. {copyright} {ital 1997} {ital The American Physical Society}
Precision study of ground state capture in the 14N(p,gamma)15O reaction
Marta, M; Gyurky, Gy; Bemmerer, D; Broggini, C; Caciolli, A; Corvisiero, P; Costantini, H; Elekes, Z; Fülöp, Z; Gervino, G; Guglielmetti, A; Gustavino, C; Imbriani, G; Junker, M; Kunz, R; Lemut, A; Limata, B; Mazzocchi, C; Menegazzo, R; Prati, P; Roca, V; Rolfs, C; Romano, M; Alvarez, C Rossi; Somorjai, E; Straniero, O; Strieder, F; Terrasi, F; Trautvetter, H P; Vomiero, A
2008-01-01
The rate of the hydrogen-burning carbon-nitrogen-oxygen (CNO) cycle is controlled by the slowest process, 14N(p,gamma)15O, which proceeds by capture to the ground and several excited states in 15O. Previous extrapolations for the ground state contribution disagreed by a factor 2, corresponding to 15% uncertainty in the total astrophysical S-factor. At the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy, a new experiment on ground state capture has been carried out at 317.8, 334.4, and 353.3 keV center-of-mass energy. Systematic corrections have been reduced considerably with respect to previous studies by using a Clover detector and by adopting a relative analysis. The previous discrepancy has been resolved, and ground state capture no longer dominates the uncertainty of the total S-factor.
Spin waves treatment of the antiferromagnetic ground state of two Ising-like systems
Directory of Open Access Journals (Sweden)
Adegoke Kunle
2014-01-01
Full Text Available Using Anderson's spin wave theory, we derive expressions for the ground state energy of two Ising-like systems. Antiferromagnetic long range order is predicted for one of the systems.
Mirzaei, Seyed Iman; Stricker, Damien; Hancock, Jason N; Berthod, Christophe; Georges, Antoine; van Heumen, Erik; Chan, Mun K; Zhao, Xudong; Li, Yuan; Greven, Martin; Barišić, Neven; van der Marel, Dirk
2013-04-09
Cuprate high-Tc superconductors exhibit enigmatic behavior in the nonsuperconducting state. For carrier concentrations near "optimal doping" (with respect to the highest Tcs) the transport and spectroscopic properties are unlike those of a Landau-Fermi liquid. On the Mott-insulating side of the optimal carrier concentration, which corresponds to underdoping, a pseudogap removes quasi-particle spectral weight from parts of the Fermi surface and causes a breakup of the Fermi surface into disconnected nodal and antinodal sectors. Here, we show that the near-nodal excitations of underdoped cuprates obey Fermi liquid behavior. The lifetime τ(ω, T) of a quasi-particle depends on its energy ω as well as on the temperature T. For a Fermi liquid, 1/τ(ω, T) is expected to collapse on a universal function proportional to (ℏω)(2) + (pπk(B)T)(2). Magneto-transport experiments, which probe the properties in the limit ω = 0, have provided indications for the presence of a T(2) dependence of the dc (ω = 0) resistivity of different cuprate materials. However, Fermi liquid behavior is very much about the energy dependence of the lifetime, and this can only be addressed by spectroscopic techniques. Our optical experiments confirm the aforementioned universal ω- and T dependence of 1/τ(ω, T), with p ∼ 1.5. Our data thus provide a piece of evidence in favor of a Fermi liquid-like scenario of the pseudogap phase of the cuprates.
Entanglement spectra of superconductivity ground states on the honeycomb lattice
Predin, Sonja; Schliemann, John
2017-12-01
We analytically evaluate the entanglement spectra of the superconductivity states in graphene, primarily focusing on the s-wave and chiral d x2- y2 + id xy superconductivity states. We demonstrate that the topology of the entanglement Hamiltonian can differ from that of the subsystem Hamiltonian. In particular, the topological properties of the entanglement Hamiltonian of the chiral d x2- y2 + id xy superconductivity state obtained by tracing out one spin direction clearly differ from those of the time-reversal invariant Hamiltonian of noninteracting fermions on the honeycomb lattice.
Ground-state fine structure in the boron isoelectronic sequence
Das, B. P.; Hata, J.; Grant, I. P.
1984-01-01
Reference is made to the study by Hata et al. (1983), which showed that MCDF-EAL calculations (Grant et al., 1980; McKenzie et al., 1980) largely remove the discrepancies between theory and experiment so long as pure hydrogenic corrections for electron self energy are used. Similar methods are applied here to the ground 2P interval in the boron isoelectronic sequence, and the results thus obtained are compared with experiment and with other recent calculations (Froese Fischer, 1983; Frye et al., 1983). It is found the the MCDF-EAL method gives very good quality results when the transition energies for delta n are equal to 0. The discrepancy between the three-configuration results and experiment is comparable with quoted experiment errors; in about half the cases it lies within the error limits, with no systematic dependence on atomic number.
On asymptotic stability in energy space of ground states of NLS in 2D
Cuccagna, Scipio; Tarulli, Mirko
2009-01-01
We transpose work by K.Yajima and by T.Mizumachi to prove dispersive and smoothing estimates for dispersive solutions of the linearization at a ground state of a Nonlinear Schr\\"odinger equation (NLS) in 2D. As an application we extend to dimension 2D a result on asymptotic stability of ground states of NLS proved in the literature for all dimensions different from 2.
On asymptotic stability in energy space of ground states of NLS in 2D
Cuccagna, Scipio; Tarulli, Mirko
2009-07-01
We transpose work by K.Yajima and by T.Mizumachi to prove dispersive and smoothing estimates for dispersive solutions of the linearization at a ground state of a Nonlinear Schr\\"odinger equation (NLS) in 2D. As an application we extend to dimension 2D a result on asymptotic stability of ground states of NLS proved in the literature for all dimensions different from 2.
Theoretical Grounds of Formation of the Efficient State Economic Policy
Directory of Open Access Journals (Sweden)
Semyrak Oksana S.
2013-12-01
Full Text Available The article conducts historical and analytical analysis of views on the role of state administration in the sphere of economic relations by various economic directions in order to allocate traditional and newest essential reference points of the modern theory of state regulation of economy. It identifies specific features of modern models of economic policy that envisage setting goals by the state, selection of relevant efficient tools and mathematic function, which would describe dependencies between them. It considers the concept of the basic theory of economic policy of Jan Tinbergen, its advantages and shortcomings. It studies prerequisites and conducts analysis of the modern concept of the role of state in economy as a subject of the market. It considers the modern concept of economic socio-dynamics, pursuant to which the main task of the state is maximisation of social usefulness and permanent improvement of the Pareto-optimal. It considers the “socio-dynamic multiplicator” notion, which envisages availability of three main components: social effect from activity of the state, yearning of individuals for creation of something new and availability of formal and informal institutions that united first two elements.
Experimental linear-optics simulation of ground-state of an Ising spin chain.
Xue, Peng; Zhan, Xian; Bian, Zhihao
2017-05-19
We experimentally demonstrate a photonic quantum simulator: by using a two-spin Ising chain (an isolated dimer) as an example, we encode the wavefunction of the ground state with a pair of entangled photons. The effect of magnetic fields, leading to a critical modification of the correlation between two spins, can be simulated by just local operations. With the ratio of simulated magnetic fields and coupling strength increasing, the ground state of the system changes from a product state to an entangled state and back to another product state. The simulated ground states can be distinguished and the transformations between them can be observed by measuring correlations between photons. This simulation of the Ising model with linear quantum optics opens the door to the future studies which connect quantum information and condensed matter physics.
Energy Technology Data Exchange (ETDEWEB)
Klopp, Frederic, E-mail: klopp@math.jussieu.fr [Universite Pierre et Marie Curie, Institut de Mathematiques de Jussieu (France); Metzger, Bernd, E-mail: metzger@wias-berlin.de [Weierstrass Institute Berlin (Germany)
2011-12-15
For discrete and continuum Gross-Pitaevskii energy functionals with a random background potential, we study the Gross-Pitaevskii ground state. We characterize a regime of interaction coupling when the Gross-Pitaevskii ground state and the ground state of the random background Hamiltonian asymptotically coincide.
Bifurcation in Ground-state Fidelity and Quantum Criticality in Two-leg Potts Ladder
Directory of Open Access Journals (Sweden)
Sheng-Hao LI
2014-02-01
Full Text Available We have investigated an intriguing connection between bifurcations, reduced fidelity per lattice site, local order parameter, universal order parameter, entropy and quantum phase transitions in the ground state for quantum three-state Potts model with two coupled infinite-size ladder system, in the context of the tensor network algorithm. The tensor network algorithm produces degenerate symmetry-breaking ground-state wave functions arising from the Z3 symmetry breaking, each of results from a randomly chosen initial state. We expect that our approach might provide further insights into critical phenomena in quantum many-body infinite lattice systems in condensed matter physics.
Excited-state properties from ground-state DFT descriptors: A QSPR approach for dyes.
Fayet, Guillaume; Jacquemin, Denis; Wathelet, Valérie; Perpète, Eric A; Rotureau, Patricia; Adamo, Carlo
2010-02-26
This work presents a quantitative structure-property relationship (QSPR)-based approach allowing an accurate prediction of the excited-state properties of organic dyes (anthraquinones and azobenzenes) from ground-state molecular descriptors, obtained within the (conceptual) density functional theory (DFT) framework. The ab initio computation of the descriptors was achieved at several levels of theory, so that the influence of the basis set size as well as of the modeling of environmental effects could be statistically quantified. It turns out that, for the entire data set, a statistically-robust four-variable multiple linear regression based on PCM-PBE0/6-31G calculations delivers a R(adj)(2) of 0.93 associated to predictive errors allowing for rapid and efficient dye design. All the selected descriptors are independent of the dye's family, an advantage over previously designed QSPR schemes. On top of that, the obtained accuracy is comparable to the one of the today's reference methods while exceeding the one of hardness-based fittings. QSPR relationships specific to both families of dyes have also been built up. This work paves the way towards reliable and computationally affordable color design for organic dyes. Copyright 2009 Elsevier Inc. All rights reserved.
Borromean ground state of fermions in two dimensions
DEFF Research Database (Denmark)
G. Volosniev, A.; V. Fedorov, D.; S. Jensen, A.
2014-01-01
The study of quantum mechanical bound states is as old as quantum theory itself. Yet, it took many years to realize that three-body borromean systems that are bound when any two-body subsystem is unbound are abundant in nature. Here we demonstrate the existence of borromean systems of spin-polari...
Ordered ground states of metallic hydrogen and deuterium
Ashcroft, N. W.
1981-01-01
The physical attributes of some of the more physically distinct ordered states of metallic hydrogen and metallic deuterium at T = 0 and nearby are discussed. The likelihood of superconductivity in both is considered with respect to the usual coupling via the density fluctuations of the ions.
Optical Feshbach resonances and ground-state-molecule production in the RbHg system
Borkowski, Mateusz; Muñoz Rodriguez, Rodolfo; Kosicki, Maciej B.; Ciuryło, Roman; Żuchowski, Piotr S.
2017-12-01
We present the prospects for photoassociation, optical control of interspecies scattering lengths, and, finally, the production of ultracold absolute ground-state molecules in the Rb+Hg system. We use the state-of-the-art ab initio methods for the calculations of ground- [CCSD(T)] and excited-state (EOM-CCSD) potential curves. The RbHg system, thanks to the wide range of stable Hg bosonic isotopes, offers possibilities for mass tuning of ground-state interactions. The optical lengths describing the strengths of optical Feshbach resonances near the Rb transitions are favorable even at large laser detunings. Ground-state RbHg molecules can be produced with efficiencies ranging from about 20% for deeply bound to at least 50% for weakly bound states close to the dissociation limit. Finally, electronic transitions with favorable Franck-Condon factors can be found for the purposes of a STIRAP transfer of the weakly bound RbHg molecules to the absolute ground state using commercially available lasers.
Bandyopadhyay, Subhajit; Roy, Saswata
2014-01-01
This paper describes an inexpensive experiment to determine the carbonyl stretching frequency of an organic keto compound in its ground state and first electronic excited state. The experiment is simple to execute, clarifies some of the fundamental concepts of spectroscopy, and is appropriate for a basic spectroscopy laboratory course. The…
Degenerate ground states and multiple bifurcations in a two-dimensional q-state quantum Potts model.
Dai, Yan-Wei; Cho, Sam Young; Batchelor, Murray T; Zhou, Huan-Qiang
2014-06-01
We numerically investigate the two-dimensional q-state quantum Potts model on the infinite square lattice by using the infinite projected entangled-pair state (iPEPS) algorithm. We show that the quantum fidelity, defined as an overlap measurement between an arbitrary reference state and the iPEPS ground state of the system, can detect q-fold degenerate ground states for the Z_{q} broken-symmetry phase. Accordingly, a multiple bifurcation of the quantum ground-state fidelity is shown to occur as the transverse magnetic field varies from the symmetry phase to the broken-symmetry phase, which means that a multiple-bifurcation point corresponds to a critical point. A (dis)continuous behavior of quantum fidelity at phase transition points characterizes a (dis)continuous phase transition. Similar to the characteristic behavior of the quantum fidelity, the magnetizations, as order parameters, obtained from the degenerate ground states exhibit multiple bifurcation at critical points. Each order parameter is also explicitly demonstrated to transform under the Z_{q} subgroup of the symmetry group of the Hamiltonian. We find that the q-state quantum Potts model on the square lattice undergoes a discontinuous (first-order) phase transition for q=3 and q=4 and a continuous phase transition for q=2 (the two-dimensional quantum transverse Ising model).
Cooling a micromechanical resonator to its ground state by measurement and feedback
DEFF Research Database (Denmark)
Bergenfeldt, Christian; Mølmer, Klaus
2009-01-01
We present an analysis of the cooling of a micromechanical resonator by means of measurement and feedback. The measurements are performed via the coupling to a Cooper-pair box, and although the coupling does not lead to net cooling, the extraction of information and hence entropy from the system...... leads to a pure quantum state. Under suitable circumstances, the states become very close to coherent states, conditioned on the measurement record, and can hence be displaced to the oscillator ground state....
Mandrà, Salvatore; Zhu, Zheng; Katzgraber, Helmut G
2017-02-17
We study the performance of the D-Wave 2X quantum annealing machine on systems with well-controlled ground-state degeneracy. While obtaining the ground state of a spin-glass benchmark instance represents a difficult task, the gold standard for any optimization algorithm or machine is to sample all solutions that minimize the Hamiltonian with more or less equal probability. Our results show that while naive transverse-field quantum annealing on the D-Wave 2X device can find the ground-state energy of the problems, it is not well suited in identifying all degenerate ground-state configurations associated with a particular instance. Even worse, some states are exponentially suppressed, in agreement with previous studies on toy model problems [New J. Phys. 11, 073021 (2009)NJOPFM1367-263010.1088/1367-2630/11/7/073021]. These results suggest that more complex driving Hamiltonians are needed in future quantum annealing machines to ensure a fair sampling of the ground-state manifold.
Ground-state configuration of neutron-rich 35Al via Coulomb breakup
Chakraborty, S.; Datta, Ushasi; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chartier, M.; Cortina-Gil, D.; De Angelis, G.; Fernandez, P. Diaz; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Johansson, H.; Jonson, B.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Plag, R.; Rahaman, A.; Reifarth, R.; Ricciardi, M. V.; Rigollet, C.; Rossi, D.; Scheidenberger, C.; Scheit, H.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Utsuno, Y.; Wagner, A.; Wamers, F.; Weick, H.; Winfield, J. S.
2017-09-01
The ground-state configuration of 35Al has been studied via Coulomb dissociation (CD) using the LAND-FRS setup (GSI, Darmstadt) at a relativistic energy of ˜403 MeV/nucleon. The measured inclusive differential CD cross section for 35Al, integrated up to 5.0 MeV relative energy between the 34Al core and the neutron using a Pb target, is 78(13) mb. The exclusive measured CD cross section that populates various excited states of 34Al is 29(7) mb. The differential CD cross section of 35Al→34Al+n has been interpreted in the light of a direct breakup model, and it suggests that the possible ground-state spin and parity of 35Al could be, tentatively, 1 /2+ or 3 /2+ or 5 /2+ . The valence neutrons, in the ground state of 35Al, may occupy a combination of either l =3 ,0 or l =1 ,2 orbitals coupled with the 34Al core in the ground and isomeric state(s), respectively. This hints of a particle-hole configuration of the neutron across the magic shell gaps at N =20 ,28 which suggests narrowing the magic shell gap. If the 5 /2+ is the ground-state spin-parity of 35Al as suggested in the literature, then the major ground-state configuration of 35Al is a combination of 34Al(g.s.;4-) ⊗νp3/2 and 34Al(isomer;1+) ⊗νd3/2 states. The result from this experiment has been compared with that from a previous knockout measurement and a calculation using the SDPF-M interaction.
Cooling a Single Atom in an Optical Tweezer to Its Quantum Ground State
Directory of Open Access Journals (Sweden)
A. M. Kaufman
2012-11-01
Full Text Available We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of about 90%. We further observe coherent control of the spin and motional state of the trapped atom. Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling. This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms. For example, these results will improve current optical-tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.
Ground states and critical points for generalized Frenkel-Kontorova models
De La Llave, R
2006-01-01
We consider a multidimensional model of Frenkel-Kontorova type but we allownon-nearest neighbor interactions.For every possible frequancy vector, weshow that there are quasi-periodicground states which enjoy further geometric properties.The gound states we produce are either bigger orsmaller than the state. They are are at bounded distance fromthe plane wave with the given frequency.The comparison property above implies that theground states and the translations are organized intolaminations. If these leave a gap, we showthat there are critical points inside the gap whichalso satisfy the comparizon properties.In particular, given any frequency, we showthat either there is a continuous parameter ofground states or there is a ground state andanother critical point which is not a ground state.
Filatov, Michael; Martínez, Todd J.; Kim, Kwang S.
2017-08-01
An extended variant of the spin-restricted ensemble-referenced Kohn-Sham (REKS) method, the REKS(4,4) method, designed to describe the ground electronic states of strongly multireference systems is modified to enable calculation of excited states within the time-independent variational formalism. The new method, the state-interaction state-averaged REKS(4,4), i.e., SI-SA-REKS(4,4), is capable of describing several excited states of a molecule involving double bond cleavage, polyradical character, or multiple chromophoric units. We demonstrate that the new method correctly describes the ground and the lowest singlet excited states of a molecule (ethylene) undergoing double bond cleavage. The applicability of the new method for excitonic states is illustrated with π stacked ethylene and tetracene dimers. We conclude that the new method can describe a wide range of multireference phenomena.
Paccione, John D; Dziewulski, David M; Young, Pamela L
2017-10-01
The New York State Department of Health developed regulations for the design and operation of spray grounds to address the potential for recreational water illnesses associated with this type of venue. The water treatment component of the new regulation was based on a first-principles approach to address the unique challenges of spray grounds. The regulation departs from traditional recreational water treatment methods by requiring a novel filtration approach and the installation of UV disinfection. The water treatment system was also required to incorporate automatic control systems to ensure the water quality is maintained with a minimum of operator involvement. The treatment process specifications were based on pathogen and contaminant loadings that are likely to be encountered at spray grounds. The regulation was finalized in 2007, giving New York State a reliable means of protecting the health of spray ground patrons.
Ground-state energy of the q-state Potts model: The minimum modularity.
Lee, J S; Hwang, S; Yeo, J; Kim, D; Kahng, B
2014-11-01
A wide range of interacting systems can be described by complex networks. A common feature of such networks is that they consist of several communities or modules, the degree of which may quantified as the modularity. However, even a random uncorrelated network, which has no obvious modular structure, has a finite modularity due to the quenched disorder. For this reason, the modularity of a given network is meaningful only when it is compared with that of a randomized network with the same degree distribution. In this context, it is important to calculate the modularity of a random uncorrelated network with an arbitrary degree distribution. The modularity of a random network has been calculated [Reichardt and Bornholdt, Phys. Rev. E 76, 015102 (2007)PLEEE81539-375510.1103/PhysRevE.76.015102]; however, this was limited to the case whereby the network was assumed to have only two communities, and it is evident that the modularity should be calculated in general with q(≥2) communities. Here we calculate the modularity for q communities by evaluating the ground-state energy of the q-state Potts Hamiltonian, based on replica symmetric solutions assuming that the mean degree is large. We found that the modularity is proportional to 〈sqrt[k]〉/〈k〉 regardless of q and that only the coefficient depends on q. In particular, when the degree distribution follows a power law, the modularity is proportional to 〈k〉^{-1/2}. Our analytical results are confirmed by comparison with numerical simulations. Therefore, our results can be used as reference values for real-world networks.
Ground Water Atlas of the United States: Introduction and national summary
Miller, James A.
1999-01-01
The Ground Water Atlas of the United States provides a summary of the most important information available for each principal aquifer, or rock unit that will yield usable quantities of water to wells, throughout the 50 States, Puerto Rico, and the U.S. Virgin Islands. The Atlas is an outgrowth of the Regional Aquifer-System Analysis (RASA) program of the U.S. Geological Survey (USGS), a program that investigated 24 of the most important aquifers and aquifer systems of the Nation and one in the Caribbean Islands (fig. 1). The objectives of the RASA program were to define the geologic and hydrologic frameworks of each aquifer system, to assess the geochemistry of the water in the system, to characterize the ground-water flow system, and to describe the effects of development on the flow system. Although the RASA studies did not cover the entire Nation, they compiled much of the data needed to make the National assessments of ground-water resources presented in the Ground Water Atlas of the United States. The Atlas, however, describes the location, extent, and geologic and hydrologic characteristics of all the important aquifers in the United States, including those not studied by the RASA program. The Atlas is written so that it can be understood by readers who are not hydrologists. Simple language is used to explain technical terms. The principles that control the presence, movement, and chemical quality of ground water in different climatic, topographic, and geologic settings are clearly illustrated. The Atlas is, therefore, useful as a teaching tool for introductory courses in hydrology or hydrogeology at the college level and as an overview of ground-water conditions for consultants who need information about an individual aquifer. It also serves as an introduction to regional and National ground-water resources for lawmakers, personnel of local, State, or Federal agencies, or anyone who needs to understand ground-water occurrence, movement, and quality. The
Hydrogeologic factors that influence ground water movement in the desert southwest United States
Chuang, Frank C.; McKee, Edwin H.; Howard, Keith A.
2003-01-01
A project to study ground-water and surface-water interactions in the desert southwestern United States was initiated in 2001 by the Tucson, Arizona office of the Water Resources Division, U.S. Geological Survey (USGS). One of the goals of the Southwest Ground-water Resources Project was to develop a regional synthesis that includes the use of available digital geologic data, which is growing rapidly due to the increasing use of Geographic Information Systems (GIS). Included in this report are the digital maps and databases of geologic information that should have a direct impact on the studies of ground-water flow and surface-water interaction. Ground-water flow is governed by many geologic factors or elements including rock and soil permeability, stratigraphy and structural features. These elements directly influence ground-water flow, which is key to understanding the possible inter-connectivity of aquifer systems in desert basins of the southwestern United States. We derive these elements from the evaluation of regional geology and localized studies of hydrogeologic basins. These elements can then be applied to other unstudied areas throughout the desert southwest. This report presents a regional perspective of the geologic elements controlling ground-water systems in the desert southwest that may eventually lead to greater focus on smaller sub-regions and ultimately, to individual ground-water basins.
Kondo scaling of the pseudogap in CeOs{sub 4}Sb{sub 12} and CeFe{sub 4}P{sub 12}
Energy Technology Data Exchange (ETDEWEB)
Rayjada, P A; Matsunami, M; Tsuda, S; Yokoya, T; Shin, S [Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Chainani, A [Institute for Plasma Research, Bhat, Gandhinagar-382 428 (India); Taguchi, M [RIKEN Harima Institute, Sayo-gun, Hyogo 679-5148 (Japan); Sugawara, H [Faculty of the Integrated Arts and Sciences, University of Tokushima, Tokushima 770-8502 (Japan); Sato, H, E-mail: pratipal@ipr.res.i [Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan)
2010-03-10
CeOs{sub 4}Sb{sub 12} and CeFe{sub 4}P{sub 12} are classified as Kondo semiconductors, which show coupled changes in electrical transport, thermodynamic and magnetic properties with a low-temperature semiconductor-like electrical resistivity. We have carried out core level and valence band photoemission spectroscopy on single crystal CeOs{sub 4}Sb{sub 12} and CeFe{sub 4}P{sub 12} to study their electronic structure and the evolution of states at the Fermi level as a function of temperature (approx10-300 K). The Ce 3d core level spectra show the presence of f{sup 0}, f{sup 1} and f{sup 2} final states with very different relative intensities in the two compounds. Single-impurity Anderson model calculations provide f electron counts of n{sub f} = 0.97 and 0.86 per Ce atom, suggestive of a low- and high-T{sub K} (= single ion Kondo temperature) for CeOs{sub 4}Sb{sub 12} and CeFe{sub 4}P{sub 12}, respectively. The high-resolution temperature-dependent near-Fermi level spectra show pseudogaps of energy approx 50 meV and approx 110 meV in the valence band density of states (DOS) of CeOs{sub 4}Sb{sub 12} and CeFe{sub 4}P{sub 12}, respectively. The temperature dependence of the DOS at the Fermi level follows the change in effective magnetic moment estimated from magnetic susceptibility for both materials, confirming the Kondo nature of the pseudogap in CeOs{sub 4}Sb{sub 12} and CeFe{sub 4}P{sub 12}. A compilation of measured pseudogaps using photoemission and optical spectroscopy identifies the charge gaps DELTA{sub C} for Ce-based Kondo semiconductors and provides a direct relation with T{sub K} given by DELTA{sub C} approx 2k{sub B}T{sub K}. In conjunction with the known behaviour of the spin gaps DELTA{sub S} approx k{sub B}T{sub K}, the results establish the coupled energy scaling of the spin and charge gaps in Kondo semiconductors.
Modeling of the stress-strain state of the ground mass contaminated with peracetic acid
Directory of Open Access Journals (Sweden)
Levenko Anna
2017-01-01
Full Text Available None of the methods described previously provides a solution to the problem that deals with the SSS evaluation of the ground mass which is under the influence of chemically active substances and, in particular, under the influence of peracetic acid. The stress-strain state of the ground mass contaminated with peracetic acid was estimated. Stresses occurring in the ground mass in the natural state were determined after the entry of acid into it and after the chemical fixation of it with sodium silicate. All the parameters of the stress-strain state of the ground mass were obtained under a number of physical and mechanical conditions. It was determined that following the work on the silicatization of the ground mass contaminated with peracetic acid the quantity of strain decreased by 26.11 to 48.9%. The comparison of the results of stress calculations indicates the stress reduction in the ground mass in 1.8 – 2.6 times after its fixing.
Structural Distortion Stabilizing the Antiferromagnetic and Semiconducting Ground State of BaMn2As2
Directory of Open Access Journals (Sweden)
Ekkehard Krüger
2016-09-01
Full Text Available We report evidence that the experimentally found antiferromagnetic structure as well as the semiconducting ground state of BaMn 2 As 2 are caused by optimally-localized Wannier states of special symmetry existing at the Fermi level of BaMn 2 As 2 . In addition, we find that a (small tetragonal distortion of the crystal is required to stabilize the antiferromagnetic semiconducting state. To our knowledge, this distortion has not yet been established experimentally.
Van der Waals potential and vibrational energy levels of the ground state radon dimer
Sheng, Xiaowei; Qian, Shifeng; Hu, Fengfei
2017-08-01
In the present paper, the ground state van der Waals potential of the Radon dimer is described by the Tang-Toennies potential model, which requires five essential parameters. Among them, the two dispersion coefficients C6 and C8 are estimated from the well determined dispersion coefficients C6 and C8 of Xe2. C10 is estimated by using the approximation equation that C6C10/C82 has an average value of 1.221 for all the rare gas dimers. With these estimated dispersion coefficients and the well determined well depth De and Re the Born-Mayer parameters A and b are derived. Then the vibrational energy levels of the ground state radon dimer are calculated. 40 vibrational energy levels are observed in the ground state of Rn2 dimer. The last vibrational energy level is bound by only 0.0012 cm-1.
Tree based machine learning framework for predicting ground state energies of molecules
Himmetoglu, Burak
2016-10-01
We present an application of the boosted regression tree algorithm for predicting ground state energies of molecules made up of C, H, N, O, P, and S (CHNOPS). The PubChem chemical compound database has been incorporated to construct a dataset of 16 242 molecules, whose electronic ground state energies have been computed using density functional theory. This dataset is used to train the boosted regression tree algorithm, which allows a computationally efficient and accurate prediction of molecular ground state energies. Predictions from boosted regression trees are compared with neural network regression, a widely used method in the literature, and shown to be more accurate with significantly reduced computational cost. The performance of the regression model trained using the CHNOPS set is also tested on a set of distinct molecules that contain additional Cl and Si atoms. It is shown that the learning algorithms lead to a rich and diverse possibility of applications in molecular discovery and materials informatics.
Ground State Properties of the 1/2 Flux Harper Hamiltonian
Kennedy, Colin; Burton, William Cody; Chung, Woo Chang; Ketterle, Wolfgang
2015-05-01
The Harper Hamiltonian describes the motion of charged particles in an applied magnetic field - the spectrum of which exhibits the famed Hofstadter's butterfly. Recent advances in driven optical lattices have made great strides in simulating nontrivial Hamiltonians, such as the Harper model, in the time-averaged sense. We report on the realization of the ground state of bosons in the Harper Hamiltonian for 1/2 flux per plaquette utilizing a tilted two-dimensional lattice with laser assisted tunneling. We detail progress in studying various ground state properties of the 1/2 flux Harper Hamiltonian including ground state degeneracies, gauge-dependent observables, effects of micromotion, adiabatic loading schemes, and emergence and decay of coherence. Additionally, we describe prospects for flux rectification using a period-tripled superlattice and generalizations to three dimensions. MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, Department of Physics, Massachusetts Institute of Technology.
Ground state properties of a laterally confined two-dimensional electron gas
Dandrea, L.; Pederiva, F.; Lipparini, E.
2009-04-01
We present an accurate diffusion Monte Carlo computation of the ground state of a two-dimensional electron gas laterally confined by a harmonic potential in the effective mass-dielectric constant approximation. The computation is made explicitly including the second dimension, and can therefore address the occurrence of phase transitions in the system. The system was studied as a function of the one-dimensional Wigner-Seitz parameter rs=1/2ρ1D in the range 0.5≤rs≤7 . The ground state is found to be spin polarized for rs>3 .
Observation of the ground-state geometric phase in a Heisenberg XY model.
Peng, Xinhua; Wu, Sanfeng; Li, Jun; Suter, Dieter; Du, Jiangfeng
2010-12-10
Geometric phases play a central role in a variety of quantum phenomena, especially in condensed matter physics. Recently, it was shown that this fundamental concept exhibits a connection to quantum phase transitions where the system undergoes a qualitative change in the ground state when a control parameter in its Hamiltonian is varied. Here we report the first experimental study using the geometric phase as a topological test of quantum transitions of the ground state in a Heisenberg XY spin model. Using NMR interferometry, we measure the geometric phase for different adiabatic circuits that do not pass through points of degeneracy.
Ground state of the hydrogen atom via Dirac equation in a minimal-length scenario
Energy Technology Data Exchange (ETDEWEB)
Antonacci Oakes, T.L.; Francisco, R.O.; Fabris, J.C.; Nogueira, J.A. [Universidade Federal do Espirito Santo, Departamento de Fisica, Vitoria (Brazil)
2013-07-15
In this work we calculate the correction to the ground state energy of the hydrogen atom due to contributions arising from the presence of a minimal length. The minimal-length scenario is introduced by means of modifying the Dirac equation through a deformed Heisenberg algebra (Kempf algebra). With the introduction of the Coulomb potential in the new Dirac energy operator, we calculate the energy shift of the ground state of the hydrogen atom in first order of the parameter related to the minimal length via perturbation theory. (orig.)
Ground-state configuration of neutron-rich Aluminum isotopes through Coulomb Breakup
Directory of Open Access Journals (Sweden)
Chakraborty S.
2014-03-01
Full Text Available Neutron-rich 34,35Al isotopes have been studied through Coulomb excitation using LAND-FRS setup at GSI, Darmstadt. The method of invariant mass analysis has been used to reconstruct the excitation energy of the nucleus prior to decay. Comparison of experimental CD cross-section with direct breakup model calculation with neutron in p3/2 orbital favours 34Al(g.s⊗νp3/2 as ground state configuration of 35Al. But ground state configuration of 34Al is complicated as evident from γ-ray spectra of 33Al after Coulomb breakup of 34Al.
Ground-state configuration of neutron-rich Aluminum isotopes through Coulomb Breakup
Chakraborty, S.; Datta Pramanik, U.; Aumann, T.; Beceiro, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chatterjee, S.; Chartier, M.; Cortina-Gil, D.; De Angelis, G.; Gonzalez-Diaz, D.; Emling, H.; Diaz Fernandez, P.; Fraile, L. M.; Ershova, O.; Geissel, H.; Heil, M.; Jonson, B.; Kelic, A.; Johansson, H.; Kruecken, R.; Kroll, T.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Munzenberg, G.; Marganiec, J.; Nociforo, C.; Najafi, A.; Panin, V.; Paschalis, S.; Pietri, S.; Plag, R.; Rahaman, A.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Ray, J.; Simon, H.; Scheidenberger, C.; Typel, S.; Taylor, J.; Togano, Y.; Volkov, V.; Weick, H.; Wagner, A.; Wamers, F.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.
2014-03-01
Neutron-rich 34,35Al isotopes have been studied through Coulomb excitation using LAND-FRS setup at GSI, Darmstadt. The method of invariant mass analysis has been used to reconstruct the excitation energy of the nucleus prior to decay. Comparison of experimental CD cross-section with direct breakup model calculation with neutron in p3/2 orbital favours 34Al(g.s)⊗νp3/2 as ground state configuration of 35Al. But ground state configuration of 34Al is complicated as evident from γ-ray spectra of 33Al after Coulomb breakup of 34Al.
Fission barriers and asymmetric ground states in the relativistic mean-field theory
Energy Technology Data Exchange (ETDEWEB)
Rutz, K. [Frankfurt Univ. (Germany). Inst. fuer Theoretische Physik; Maruhn, J.A. [Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 87831 (United States); Reinhard, P.G. [Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 87831 (United States); Greiner, W. [Joint Institute for Heavy Ion Research, Holifield Heavy Ion Research Facility, Oak Ridge, TN 87831 (United States)
1995-07-31
The symmetric and asymmetric fission path for {sup 240}Pu, {sup 232}Th and {sup 226}Ra is investigated within the relativistic mean-field model. Standard parametrizations which are well fitted to nuclear ground-state properties are found to deliver reasonable qualitative and quantitative features of fission, comparable to similar nonrelativistic calculations. Furthermore, stable octupole deformations in the ground states of radium isotopes are investigated. They are found in a series of isotopes, qualitatively in agreement with nonrelativistic models. But the quantitative details differ amongst the models and between the various relativistic parametrizations. (orig.).
Klein-Gordon lower bound to the semirelativistic ground-state energy
Energy Technology Data Exchange (ETDEWEB)
Hall, Richard L., E-mail: rhall@mathstat.concordia.c [Department of Mathematics and Statistics, Concordia University, 1455 de Maisonneuve Boulevard West, Montreal, Quebec, H3G 1M8 (Canada); Lucha, Wolfgang, E-mail: wolfgang.lucha@oeaw.ac.a [Institute for High Energy Physics, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna (Austria)
2010-04-19
For the class of attractive potentials V(r)<=0 which vanish at infinity, we prove that the ground-state energy E of the semirelativistic Hamiltonian H=sq root(m{sup 2}+p{sup 2})+V(r) is bounded below by the ground-state energy e of the corresponding Klein-Gordon problem (p{sup 2}+m{sup 2})phi=(V(r)-e){sup 2}phi. Detailed results are presented for the exponential and Woods-Saxon potentials.
Machine Learning Technique to Find Quantum Many-Body Ground States of Bosons on a Lattice
Saito, Hiroki; Kato, Masaya
2018-01-01
We have developed a variational method to obtain many-body ground states of the Bose-Hubbard model using feedforward artificial neural networks. A fully connected network with a single hidden layer works better than a fully connected network with multiple hidden layers, and a multilayer convolutional network is more efficient than a fully connected network. AdaGrad and Adam are optimization methods that work well. Moreover, we show that many-body ground states with different numbers of particles can be generated by a single network.
Ground state atomic oxygen in high-power impulse magnetron sputtering: a quantitative study
Britun, Nikolay; Belosludtsev, Alexandr; Silva, Tiago; Snyders, Rony
2017-02-01
The ground state density of oxygen atoms in reactive high-power impulse magnetron sputtering discharges has been studied quantitatively. Both time-resolved and space-resolved measurements were conducted. The measurements were performed using two-photon absorption laser-induced fluorescence (TALIF), and calibrated by optical emission actinometry with multiple Ar emission lines. The results clarify the dynamics of the O ground state atoms in the discharge afterglow significantly, including their propagation and fast decay after the plasma pulse, as well as the influence of gas pressure, O2 admixture, etc.
Probing of the pseudogap via thermoelectric properties in the Au-Al-Gd quasicrystal approximant
Ishikawa, Asuka; Takagiwa, Yoshiki; Kimura, Kaoru; Tamura, Ryuji
2017-03-01
The pseudogap of the recently discovered Au-Al-Gd quasicrystal approximant crystal (AC) is investigated over a wide electron-per-atom (e /a ) ratio of ˜0.5 using thermoelectric properties as an experimental probe. This Au-Al-Gd AC provides an ideal platform for fine probing of the pseudogap among a number of known ACs because the Au-Al-Gd AC possesses an extraordinarily wide single-phase region with respect to the variation in the electron concentration [A. Ishikawa, T. Hiroto, K. Tokiwa, T. Fujii, and R. Tamura, Phys. Rev. B 93, 024416 (2016), 10.1103/PhysRevB.93.024416], in striking contrast to, for instance, binary stoichiometric C d6R ACs. As a result, a salient peak structure is observed in the Seebeck coefficient, S , with the composition as well as that of the power factor S2σ , in addition to a gradual variation in the conductivity, σ , and S . These two features are directly associated with rapid and slow variations, respectively, of spectral conductivity σ (E ) , and hence the fine structure inside the pseudogap, in the vicinity of the Fermi level EF. Based on the observed continuous variation of the Fermi wave vector reported in the previous experimental work, fine tuning of EF toward an optimal position was attempted, which led to the successful observation of a sharp peak in S2σ with a value of ˜270 μ W /m .K2 at 873 K. This is the highest value ever reported among both Tsai-type and Bergman-type compounds. The dimensionless figure of merit was determined as 0.026 at 873 K, which is also the highest reported among both Tsai-type and Bergman-type compounds.
Systematic study of α preformation probability of nuclear isomeric and ground states
Sun, Xiao-Dong; Wu, Xi-Jun; Zheng, Bo; Xiang, Dong; Guo, Ping; Li, Xiao-Hua
2017-01-01
In this paper, based on the two-potential approach combining with the isospin dependent nuclear potential, we systematically compare the α preformation probabilities of odd-A nuclei between nuclear isomeric states and ground states. The results indicate that during the process of α particle preforming, the low lying nuclear isomeric states are similar to ground states. Meanwhile, in the framework of single nucleon energy level structure, we find that for nuclei with nucleon number below the magic numbers, the α preformation probabilities of high-spin states seem to be larger than low ones. For nuclei with nucleon number above the magic numbers, the α preformation probabilities of isomeric states are larger than those of ground states. Supported by National Natural Science Foundation of China (11205083), Construct Program of Key Discipline in Hunan Province, Research Foundation of Education Bureau of Hunan Province, China (15A159), Natural Science Foundation of Hunan Province, China (2015JJ3103, 2015JJ2123), Innovation Group of Nuclear and Particle Physics in USC, Hunan Provincial Innovation Foundation for Postgraduate (CX2015B398)
Energy Technology Data Exchange (ETDEWEB)
Kleinlein, Claudia; Zheng, Shao-Liang; Betley, Theodore A.
2017-04-24
Three ferric dipyrromethene complexes featuring different ancillary ligands were synthesized by one electron oxidation of ferrous precursors. Four-coordinate iron complexes of the type (^{Ar}L)FeX_{2} [^{Ar}L = 1,9-(2,4,6-Ph_{3}C_{6}H_{2})_{2}-5-mesityldipyrromethene] with X = Cl or ^{t}BuO were prepared and found to be high-spin (S = 5/2), as determined by superconducting quantum interference device magnetometry, electron paramagnetic resonance, and ^{57}Fe Mössbauer spectroscopy. The ancillary ligand substitution was found to affect both ground state and excited properties of the ferric complexes examined. While each ferric complex displays reversible reduction and oxidation events, each alkoxide for chloride substitution results in a nearly 600 mV cathodic shift of the Fe^{III/II} couple. The oxidation event remains largely unaffected by the ancillary ligand substitution and is likely dipyrrin-centered. While the alkoxide substituted ferric species largely retain the color of their ferrous precursors, characteristic of dipyrrin-based ligand-to-ligand charge transfer (LLCT), the dichloride ferric complex loses the prominent dipyrrin chromophore, taking on a deep green color. Time-dependent density functional theory analyses indicate the weaker-field chloride ligands allow substantial configuration mixing of ligand-to-metal charge transfer into the LLCT bands, giving rise to the color changes observed. Furthermore, the higher degree of covalency between the alkoxide ferric centers is manifest in the observed reactivity. Delocalization of spin density onto the tert-butoxide ligand in (^{Ar}L)FeCl(O^{t}Bu) is evidenced by hydrogen atom abstraction to yield (^{Ar}L)FeCl and HOtBu in the presence of substrates containing weak C–H bonds, whereas the chloride (^{Ar}L)FeCl_{2} analogue does not react under these conditions.
Energy Technology Data Exchange (ETDEWEB)
Jahan, Luhluh K., E-mail: luhluhjahan@gmail.com; Chatterjee, Ashok [School of Physics, University of Hyderabad, Gachibowli, Telangana India 500046 (India)
2016-05-23
The temperature and size dependence of the ground-state energy of a polaron in a Gaussian quantum dot have been investigated by using a variational technique. It is found that the ground-state energy increases with increasing temperature and decreases with the size of the quantum dot. Also, it is found that the ground-state energy is larger for a three-dimensional quantum dot as compared to a two-dimensional dot.
Zhang, Huafeng; Chen, Fang; Yu, Chunchao; Sun, Lihui; Xu, Dahai
2017-08-01
Not Available Properties of the ground-state solitons, which exist in the spin-orbit coupling (SOC) Bose-Einstein condensates (BEC) in the presence of optical lattices, are presented. Results show that several system parameters, such as SOC strength, lattice depth, and lattice frequency, have important influences on properties of ground state solitons in SOC BEC. By controlling these parameters, structure and spin polarization of the ground-state solitons can be effectively tuned, so manipulation of atoms may be realized.
Raman cooling imaging: Detecting single atoms near their ground state of motion
Lester, Brian J.; Kaufman, Adam M.; Regal, Cindy A.
2014-01-01
We demonstrate imaging of neutral atoms via the light scattered during continuous Raman sideband cooling. We detect single atoms trapped in optical tweezers while maintaining a significant motional ground-state fraction. The techniques presented provide a framework for single-atom resolved imaging of a broad class of atomic species.
Use of ground-penetrating radar to study tree roots in the southeastern United States
John R. Butnor; J.A. Doolittle; L. Kress; Susan Cohen; Kurt H. Johnsen
2001-01-01
Summary: The objectives of our study were to assess the feasibility of using ground-penetrating radar (GPR) to study roots over a broad range of soil conditions in the southeastern United States. Study sites were located in the Southern Piedmont, Carolina Sandhills and Atlantic Coast Flatwoods. At each site, we tested for selection of the appropriate...
Singlet Ground State Magnetism: III Magnetic Excitons in Antiferromagnetic TbP
DEFF Research Database (Denmark)
Knorr, K.; Loidl, A.; Kjems, Jørgen
1981-01-01
The dispersion of the lowest magnetic excitations of the singlet ground state system TbP has been studied in the antiferromagnetic phase by inelastic neutron scattering. The magnetic exchange interaction and the magnetic and the rhombohedral molecular fields have been determined....
A large-space shell-model approach to the ground state properties of 16O
Takayanagi, K.; Lipparini, E.
1991-05-01
We perform a large-space shell-model calculation of the non-local one-body density of 16O which takes into account the two-particle-two-hole correlations in the ground state. An application is done to a simultaneous study of the matter and momentum distributions and the occupation numbers of particle levels.
Theoretical study on ground-state proton/H-atom exchange in formic ...
Indian Academy of Sciences (India)
The ground-state triple proton/H-atom transfer (GSTPT/GSTHAT) reactions in HCOOH complexed cyclically with H₂O, CH₃OH, NH₃ and mixed solvents H₂O-NH₃/CH₃ OH-NH₃ were studied byquantum mechanical methods in heptane. The GSTPT/GSTHAT in HCOOH-(H₂O) ₂, HCOOH-(CH₃OH)₂, ...
Frozen Spin Ice Ground States in the Pyrochlore Magnet Tb2Ti2O7
Fritsch, Katharina
2015-03-01
The ground state nature of the candidate spin liquid pyrochlore magnet Tb2Ti2O7 has remained a puzzle for over 15 years. Despite theoretical expectations of magnetic order below ~ 1 K based on classical Ising-like Tb 3 + spins, early μSR and neutron scattering experiments showed no long range order down to 50 mK. This motivated two theoretical scenarios to account for the apparently disordered ground state: a quantum spin ice scenario in which the classical spin order is suppressed by virtual crystal field excitations that renormalize the antiferromagnetic exchange, or a scenario arising from a yet to be observed structural distortion creating a non-magnetic singlet ground state. I will discuss our time-of-flight neutron scattering measurements on Tb2Ti2O7 that reveal a glassy spin ice ground state, characterized by frozen antiferromagnetic short range order and the formation of a ~ 0.08 meV energy gap in its spin excitation spectrum at the (1/2,1/2,1/2) quasi-ordering wave vectors. A new H - T phase diagram for Tb2Ti2O7 in [110] magnetic field will be presented. I will further discuss recent experiments on slightly off-stoichiometric Tb2+xTi2-xO7-y samples, which also display the same gapped spin ice correlations at (1/2,1/2,1/2) wave vectors.
Theoretical study of the ground state of (EDO-TTF)(2)PF6
Linker, Gerrit-Jan; van Duijnen, Piet Th.; van Loosdrecht, Paul H.M.; Broer, Ria
2015-01-01
In this paper we present a theoretical study of the nature of the ground state of the (EDO-TTF)(2)PF6 charge transfer salt by using ab initio quantum chemical theory for clusters in vacuum, for embedded clusters and for the periodic system. Exemplary for other organic charge transfer systems, we
Ground state solutions for the nonlinear Schrödinger–Maxwell equations
National Research Council Canada - National Science Library
Azzollini, A; Pomponio, A
2008-01-01
In this paper we study the nonlinear Schrodinger-Maxwell equations {-[DELTA]u+V(x)u+[phi]u=|u|.sup.p-1uin R.sup.3,-[DELTA][phi]=u.sup.2in R.sup.3. If V is a positive constant, we prove the existence of a ground state solution...
Distribution of Elevated Nitrate Concentrations in Ground Water in Washington State
Frans, Lonna
2008-01-01
More than 60 percent of the population of Washington State uses ground water for their drinking and cooking needs. Nitrate concentrations in ground water are elevated in parts of the State as a result of various land-use practices, including fertilizer application, dairy operations and ranching, and septic-system use. Shallow wells generally are more vulnerable to nitrate contamination than deeper wells (Williamson and others, 1998; Ebbert and others, 2000). In order to protect public health, the Washington State Department of Health requires that public water systems regularly measure nitrate in their wells. Public water systems serving more than 25 people collect water samples at least annually; systems serving from 2 to 14 people collect water samples at least every 3 years. Private well owners serving one residence may be required to sample when the well is first drilled, but are unregulated after that. As a result, limited information is available to citizens and public health officials about potential exposure to elevated nitrate concentrations for people whose primary drinking-water sources are private wells. The U.S. Geological Survey and Washington State Department of Health collaborated to examine water-quality data from public water systems and develop models that calculate the probability of detecting elevated nitrate concentrations in ground water. Maps were then developed to estimate ground water vulnerability to nitrate in areas where limited data are available.
Michels, M.A.J.; Suttorp, L.G.
1972-01-01
The inductive contribution to the retarded interatomic potential energy of two atoms in degenerate ground states is calculated up to all multipole orders on the basis of quantum electrodynamics. The result, which is found to have nonretarded character, is written in such a way as to show the
A theoretical study of the MgNC/MgCN isomerization in the electronic ground state
Czech Academy of Sciences Publication Activity Database
Bludský, Ota; Špirko, Vladimír; Odaka, T. E.; Jensen, P.; Hirano, T.
695/696, - (2004), s. 219-226 ISSN 0022-2860 R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4055905 Keywords : isomerization * electronic ground state * STIRAP Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.200, year: 2004
The isospin admixture of the ground state and the properties of the ...
Indian Academy of Sciences (India)
were investigated with the inclusion of the pairing correlations between nucleons for the medium and heavy mass regions: 80 < A < 90, 102 < A < 124, and 204 < A < 214. It was determined that the influence of the pairing interaction between nucleons on the isospin admixtures in the ground state and the isospin structure of ...
The excitonic ground state of the half-filled Peierls insulator
Rice, MJ; Gartstein, YN
2005-01-01
We point out that the half-filled Peierls insulator, celebrated for its soliton excitations and its application to trans(polyacetylene), is an excitonic insulator in which collectively bound electron-hole pair excitations (excitons) are mixed into the ground state. Unlike the bound electron pairs of
Ground state structures and properties of Si3Hn (n = 1–6) clusters
Indian Academy of Sciences (India)
Unknown
Abstract. The ground state structures and properties of Si3Hn (1 ≤≤ n ≤≤ 6) clusters have been calculated using. Car–Parrinello molecular dynamics with simulated annealing and steepest descent optimization methods. We have studied cohesive energy per particle and first excited electronic level gap of the clusters as ...
Entanglement perturbation theory for the quantum ground states in two dimensions
Chung, S. G.; Ueda, K.
2010-01-01
A simple, general and practically exact method, Entanglement Perturbation Theory (EPT), is formulated to calculate the ground states of 2D macroscopic quantum systems with translational symmetry. An emphasis will be placed on the applicability of EPT to fermions. We will discuss some preliminary evidences which indicate a potential of EPT.
Sequences of ground states and classification of frustration in odd-numbered antiferromagnetic rings
Florek, Wojciech; Antkowiak, Michał; Kamieniarz, Grzegorz
2016-12-01
The sequences of ground states in frustrated antiferromagnetic rings with odd number of local spins characterized by a single bond defect or by arbitrary uniform couplings to an additional spin located at the center are determined. The sequences provide firm constraints on the total ground-state quantum numbers, which are more stringent than those arising from the Lieb-Mattis theorem for bipartite quantum spin systems. Apart from their theoretical importance, they suggest the possibility of tailoring a given class of the molecular nanomagnets with desired ground-state properties by tuning the relevant couplings. In particular, they predict the spin S =1 /2 ground state for the centered rings composed of the half-integer spins with approximately uniform interactions. They confirm the applicability of the recent classification of spin frustration in both types of molecular nanomagnets. The classification is also discussed in the classical limit for the first class of the rings, providing a direct picture of frustration types. The Lieb-Mattis energy-level ordering and an analog of the Landé band, i.e., the energy spectra properties simplifying the characterization of the rings using the bulk magnetic or NMR measurements, are briefly discussed.
Ground state properties of the bond alternating spin-1/2 anisotropic Heisenberg chain
Directory of Open Access Journals (Sweden)
S. Paul
2017-06-01
Full Text Available Ground state properties, dispersion relations and scaling behaviour of spin gap of a bond alternating spin-1/2 anisotropic Heisenberg chain have been studied where the exchange interactions on alternate bonds are ferromagnetic (FM and antiferromagnetic (AFM in two separate cases. The resulting models separately represent nearest neighbour (NN AFM-AFM and AFM-FM bond alternating chains. Ground state energy has been estimated analytically by using both bond operator and Jordan-Wigner representations and numerically by using exact diagonalization. Dispersion relations, spin gap and several ground state orders have been obtained. Dimer order and string orders are found to coexist in the ground state. Spin gap is found to develop as soon as the non-uniformity in alternating bond strength is introduced in the AFM-AFM chain which further remains non-zero for the AFM-FM chain. This spin gap along with the string orders attribute to the Haldane phase. The Haldane phase is found to exist in most of the anisotropic region similar to the isotropic point.
Relativistic analysis of nuclear ground state densities at 135 to 200 ...
Indian Academy of Sciences (India)
fitting of differential cross-section and analyzing power, and the appearance of wine-bottle- bottom shaped Re Ueff (r) in the transition energy region, sensitively depends on the input nuclear ground state densities and are not solely the relativistic characteristic signatures. We also found that the wine-bottle-bottom shaped ...
Soluble and stable heptazethrenebis(dicarboximide) with a singlet open-shell ground state
Sun, Zhe
2011-08-10
A soluble and stable heptazethrene derivative was synthesized and characterized for the first time. This molecule exhibits a singlet biradical character in the ground state, which is the first case among zethrene homologue series. Exceptional stability of this heptazethrenebis(dicarboximide) raises the likelihood of its practical applications in materials science. © 2011 American Chemical Society.
The magnetic structure on the ground state of the equilateral triangular spin tube
Energy Technology Data Exchange (ETDEWEB)
Matsui, Kazuki, E-mail: k703861@eagle.sophia.ac.jp; Goto, Takayuki [Sophia University, Physics Division (Japan); Manaka, Hirotaka [Kagoshima University, Graduate School of Science and Engineering (Japan); Miura, Yoko [Suzuka National College of Technology (Japan)
2016-12-15
The ground state of the frustrated equilateral triangular spin tube CsCrF{sub 4} is still hidden behind a veil though NMR spectrum broaden into 2 T at low temperature. In order to investigate the spin structure in an ordered state by {sup 19}F-NMR, we have determined the anisotropic hyperfine coupling tensors for each three fluorine sites in the paramagnetic state. The measurement field was raised up to 10 T to achieve highest resolution. The preliminary analysis using the obtained hyperfine tensors has shown that the archetypal 120°-type structure in ab-plane does not accord with the NMR spectra of ordered state.
Directory of Open Access Journals (Sweden)
Logan D Andrews
2013-07-01
Full Text Available Enzymes stabilize transition states of reactions while limiting binding to ground states, as is generally required for any catalyst. Alkaline Phosphatase (AP and other nonspecific phosphatases are some of Nature's most impressive catalysts, achieving preferential transition state over ground state stabilization of more than 10²²-fold while utilizing interactions with only the five atoms attached to the transferred phosphorus. We tested a model that AP achieves a portion of this preference by destabilizing ground state binding via charge repulsion between the anionic active site nucleophile, Ser102, and the negatively charged phosphate monoester substrate. Removal of the Ser102 alkoxide by mutation to glycine or alanine increases the observed Pi affinity by orders of magnitude at pH 8.0. To allow precise and quantitative comparisons, the ionic form of bound P(i was determined from pH dependencies of the binding of Pi and tungstate, a P(i analog lacking titratable protons over the pH range of 5-11, and from the ³¹P chemical shift of bound P(i. The results show that the Pi trianion binds with an exceptionally strong femtomolar affinity in the absence of Ser102, show that its binding is destabilized by ≥10⁸-fold by the Ser102 alkoxide, and provide direct evidence for ground state destabilization. Comparisons of X-ray crystal structures of AP with and without Ser102 reveal the same active site and P(i binding geometry upon removal of Ser102, suggesting that the destabilization does not result from a major structural rearrangement upon mutation of Ser102. Analogous Pi binding measurements with a protein tyrosine phosphatase suggest the generality of this ground state destabilization mechanism. Our results have uncovered an important contribution of anionic nucleophiles to phosphoryl transfer catalysis via ground state electrostatic destabilization and an enormous capacity of the AP active site for specific and strong recognition of the
Three-body correlations in the ground-state decay of 26O
Kohley, Z.; Baumann, T.; Christian, G.; DeYoung, P. A.; Finck, J. E.; Frank, N.; Luther, B.; Lunderberg, E.; Jones, M.; Mosby, S.; Smith, J. K.; Spyrou, A.; Thoennessen, M.
2015-03-01
Background: Theoretical calculations have shown that the energy and angular correlations in the three-body decay of the two-neutron unbound 26O can provide information on the ground-state wave function, which has been predicted to have a dineutron configuration and 2 n halo structure. Purpose: To use the experimentally measured three-body correlations to gain insight into the properties of 26O , including the decay mechanism and ground-state resonance energy. Method: 26O was produced in a one-proton knockout reaction from 27F and the 24O+n +n decay products were measured using the MoNA-Sweeper setup. The three-body correlations from the 26O ground-state resonance decay were extracted. The experimental results were compared to Monte Carlo simulations in which the resonance energy and decay mechanism were varied. Results: The measured three-body correlations were well reproduced by the Monte Carlo simulations but were not sensitive to the decay mechanism due to the experimental resolutions. However, the three-body correlations were found to be sensitive to the resonance energy of 26O . A 1 σ upper limit of 53 keV was extracted for the ground-state resonance energy of 26O . Conclusions: Future attempts to measure the three-body correlations from the ground-state decay of 26O will be very challenging due to the need for a precise measurement of the 24O momentum at the reaction point in the target.
Radon concentrations in ground and drinking water in the state of Chihuahua, Mexico
Energy Technology Data Exchange (ETDEWEB)
Villalba, L. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Colmenero Sujo, L. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Instituto Tecnologico de Chihuahua II, Ave. de las Industrias 11101, Chihuahua, Chih. (Mexico); Montero Cabrera, M.E. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico)]. E-mail: elena.montero@cimav.edu.mx; Cano Jimenez, A. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Renteria Villalobos, M. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico); Delgado Mendoza, C.J. [Facultad de Ciencias Quimicas, Universidad Autonoma de Chihuahua, Ciudad Universitaria S/N, Chihuahua, Chih. (Mexico); Jurado Tenorio, L.A. [Facultad de Ciencias Quimicas, Universidad Autonoma de Chihuahua, Ciudad Universitaria S/N, Chihuahua, Chih. (Mexico); Davila Rangel, I. [Centro Regional de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 20, Zacatecas, Zac. (Mexico); Herrera Peraza, E.F. [Centro de Investigacion en Materiales Avanzados, S.C., Miguel de Cervantes 120, Complejo Industrial Chihuahua, CP 31109 Chihuahua, Chih. (Mexico)
2005-07-01
This paper reports {sup 222}Rn concentrations in ground and drinking water of nine cities of Chihuahua State, Mexico. Fifty percent of the 114 sampled wells exhibited {sup 222}Rn concentrations exceeding 11 Bq/L, the maximum contaminant level (MCL) recommended by the USEPA. Furthermore, around 48% (123 samples) of the tap-water samples taken from 255 dwellings showed radon concentrations over the MCL. There is an apparent correlation between total dissolved solids and radon concentration in ground-water. The high levels of {sup 222}Rn found may be entirely attributed to the nature of aquifer rocks.
Study of polonium isotopes ground state properties by simultaneous atomic- and nuclear-spectroscopy
Koester, U H; Kalaninova, Z; Imai, N
2007-01-01
We propose to systematically study the ground state properties of neutron deficient $^{192-200}$Po isotopes by means of in-source laser spectroscopy using the ISOLDE laser ion source coupled with nuclear spectroscopy at the detection setup as successfully done before by this collaboration with neutron deficient lead isotopes. The study of the change in mean square charge radii along the polonium isotope chain will give an insight into shape coexistence above the mid-shell N = 104 and above the closed shell Z = 82. The hyperfine structure of the odd isotopes will also allow determination of the nuclear spin and the magnetic moment of the ground state and of any identifiable isomer state. For this study, a standard UC$_{x}$ target with the ISOLDE RILIS is required for 38 shifts.
Landau Level Mixing and the Ground State of the ν=5/2 Quantum Hall Effect.
Rezayi, Edward H
2017-07-14
Inter-Landau-level transitions break particle hole symmetry and will choose either the Pfaffian or the anti-Pfaffian state as the absolute ground state at 5/2 filling of the fractional quantum Hall effect. An approach based on truncating the Hilbert space has favored the anti-Pfaffian. A second approach based on an effective Hamiltonian produced the Pfaffian. In this Letter, perturbation theory is applied to finite sizes without bias to any specific pseudopotential component. This method also singles out the anti-Pfaffian. A critical piece of the effective Hamiltonian, which was absent in previous studies, reverts the ground state at 5/2 to the anti-Pfaffian.
Ground-state properties of K-isotopes from laser and $\\beta$-NMR spectroscopy
Lievens, P; Rajabali, M M; Krieger, A R
By combining high-resolution laser spectroscopy with $\\beta$-NMR spectroscopy on polarized K-beams we aim to establish the ground-state spins and magnetic moments of the neutron-rich $^{48,49,50,51}$K isotopes from N=29 to N=32. Spins and magnetic moments of the odd-K isotopes up to N=28 reveal an inversion of the ground-state, from the normal $\\,{I}$=3/2 ($\\pi{d}_{3/2}^{-1}$) in $^{41-45}$K$\\to\\,{I}$=1/2 ($\\pi{s}_{1/2}^{-1}$) in $^{47}$K. This inversion of the proton single particle levels is related to the strong proton $d_{3/2}$ - neutron $f_{7/2}$ interaction which lowers the energy of the $\\pi{d}_{3/2}$ single particle state when filling the $\
Long-range magnetic fields in the ground state of the Standard Model plasma.
Boyarsky, Alexey; Ruchayskiy, Oleg; Shaposhnikov, Mikhail
2012-09-14
In thermal equilibrium the ground state of the plasma of Standard Model particles is determined by temperature and exactly conserved combinations of baryon and lepton numbers. We show that at nonzero values of the global charges a translation invariant and homogeneous state of the plasma becomes unstable and the system transits into a new equilibrium state, containing a large-scale magnetic field. The origin of this effect is the parity-breaking character of weak interactions and chiral anomaly. This situation could occur in the early Universe and may play an important role in its subsequent evolution.
Long-range magnetic fields in the ground state of the Standard Model plasma
Boyarsky, Alexey; Shaposhnikov, Mikhail
2012-01-01
In thermal equilibrium the ground state of the plasma of Standard Model particles is determined by temperature and exactly conserved combinations of baryon and lepton numbers. We show that at non-zero values of the global charges a translation invariant and homogeneous state of the plasma becomes unstable and the system transits into a new state, containing a large-scale magnetic field. The origin of this effect is the parity-breaking character of weak interactions and chiral anomaly. This situation can occur in the early Universe and may play an important role in its subsequent evolution.
Mandra, Salvatore
2017-01-01
We study the performance of the D-Wave 2X quantum annealing machine on systems with well-controlled ground-state degeneracy. While obtaining the ground state of a spin-glass benchmark instance represents a difficult task, the gold standard for any optimization algorithm or machine is to sample all solutions that minimize the Hamiltonian with more or less equal probability. Our results show that while naive transverse-field quantum annealing on the D-Wave 2X device can find the ground-state energy of the problems, it is not well suited in identifying all degenerate ground-state configurations associated to a particular instance. Even worse, some states are exponentially suppressed, in agreement with previous studies on toy model problems [New J. Phys. 11, 073021 (2009)]. These results suggest that more complex driving Hamiltonians are needed in future quantum annealing machines to ensure a fair sampling of the ground-state manifold.
Stonestrom, David A.; Harrill, James R.
2007-01-01
Ground-water recharge in the arid and semiarid southwestern United States results from the complex interplay of climate, geology, and vegetation across widely ranging spatial and temporal scales. Present-day recharge tends to be narrowly focused in time and space. Widespread water-table declines accompanied agricultural development during the twentieth century, demonstrating that sustainable ground-water supplies are not guaranteed when part of the extracted resource represents paleorecharge. Climatic controls on ground-water recharge range from seasonal cycles of summer monsoonal and winter frontal storms to multimillennial cycles of glacial and interglacial periods. Precipitation patterns reflect global-scale interactions among the oceans, atmosphere, and continents. Large-scale climatic influences associated with El Ni?o and Pacific Decadal Oscillations strongly but irregularly control weather in the study area, so that year-to-year variations in precipitation and ground-water recharge are large and difficult to predict. Proxy data indicate geologically recent periods of multidecadal droughts unlike any in the modern instrumental record. Anthropogenically induced climate change likely will reduce ground-water recharge through diminished snowpack at higher elevations, and perhaps through increased drought. Future changes in El Ni?o and monsoonal patterns, both crucial to precipitation in the study area, are highly uncertain in current models. Land-use modifications influence ground-water recharge directly through vegetation, irrigation, and impermeable area, and indirectly through climate change. High ranges bounding the study area?the San Bernadino Mountains and Sierra Nevada to the west, and the Wasatch and southern Colorado Rocky Mountains to the east?provide external geologic controls on ground-water recharge. Internal geologic controls stem from tectonic processes that led to numerous, variably connected alluvial-filled basins, exposure of extensive
Developing a state water plan: Ground-water conditions in Utah, spring of 1988
Cordy, Gail E.; Smith, G.J.; Roark, D. Michael; Lambert, Patrick M.; Yarbrough, John A.; Burden, Carole B.; Garrett, R.B.; Emett, D.C.; Thiros, Susan A.; Sandberg, G.W.; Puchta, R.W
1988-01-01
This is the twenty-fifth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions.This report, like the others in the series, contains information on well construction, ground-water withdrawals from wells, water-level changes, and related changes in precipitation and streamflow. Supplementary data such as graphs showing chemical quality of water and maps showing water-level contours are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions.This report includes individual discussions of selected major areas of ground-water development in the State for the calendar year 1987. Water-level fluctuations, however, are described from the spring of 1987 to the spring of 1988. Much of the data used in this report were collected by the U.S. Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.
Developing a state water plan: Ground-water conditions in Utah, spring of 1986
Mason, James L.; Smith, G.J.; Roark, D. Michael; Lambert, Patrick M.; Jensen, V.L.; Wilberg, Dale E.; Burden, Carole B.; Garrett, R.B.; Emett, D.C.; Duncanson, Susan; Sandberg, G.W.; Puchta, R.W; Herbert, L.R.
1986-01-01
This is the twenty-third in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions.This report, like the others in the series, contains information on well construction, ground-water withdrawals from wells, water-level changes, and related changes in precipitation and streamflow. Supplementary data such as graphs showing chemical quality of water and maps showing water-level contours are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions.This report includes individual discussions of selected major areas of ground-water development in the State for the calendar year 1985. Water-level fluctuations, however, are described from the spring of 1985 to the spring of 1986. Much of the data used in this report were collected by the U.S. Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.
Developing a state water plan: Ground-water conditions in Utah, spring of 1987
Wilberg, Dale E.; Smith, G.J.; Roark, D. Michael; Lambert, Patrick M.; Jensen, V.L.; Cordy, Gail E.; Burden, Carole B.; Enright, Michael; Emett, D.C.; Thiros, Susan A.; Sandberg, G.W.; Puchta, R.W; Herbert, L.R.
1987-01-01
This is the twenty-fourth in a Series of annual reports that describe ground-water Conditions in Utah. Reports in the series, prepared cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions.This report, like the others in the series, contains information on well Construction, ground-water withdrawals from wells, Water-level changes, and related changes in precipitation and streamflow. Supplementary data such as graphs showing chemical quality of Water and maps showing water-level contours are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions.The report includes individual discussions of Selected major areas of ground-water development in the State for the calendar year 1986. Water-level fluctuations, however, are described for spring 1986 to spring 1987. Much of the data used in the report were collected by the Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.
Structural instability and ground state of the U{sub 2}Mo compound
Energy Technology Data Exchange (ETDEWEB)
Losada, E.L., E-mail: losada@cab.cnea.gov.ar [SIM" 3, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina); Garcés, J.E. [Gerencia de Investigación y Aplicaciones Nucleares, Comisión Nacional de Energía Atómica (Argentina)
2015-11-15
This work reports on the structural instability at T = 0 °K of the U{sub 2}Mo compound in the C11{sub b} structure under the distortion related to the C{sub 66} elastic constant. The electronic properties of U{sub 2}Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11{sub b} structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U–Mo–U blocks. Hybridization due to electronic interactions inside the U–Mo–U blocks is slightly modified under the D{sub 6} distortion. The change in distance between chains modifies the U–U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U{sub 2}Mo due to the D{sub 6} distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U{sub 2}Mo compound is not the assumed C11{sub b} structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure. - Highlights: • Structural instability of the C11b compound due to the D6 deformation. • Induced Peierls distortion due to the D6 deformation. • Distorted structure is stabilized by hybridization and split of f-Uranium state. • P6 (#168) suggested ground state for the U{sub 2}Mo compound.
Kvaal, Simen; Helgaker, Trygve
2015-11-14
The relationship between the densities of ground-state wave functions (i.e., the minimizers of the Rayleigh-Ritz variation principle) and the ground-state densities in density-functional theory (i.e., the minimizers of the Hohenberg-Kohn variation principle) is studied within the framework of convex conjugation, in a generic setting covering molecular systems, solid-state systems, and more. Having introduced admissible density functionals as functionals that produce the exact ground-state energy for a given external potential by minimizing over densities in the Hohenberg-Kohn variation principle, necessary and sufficient conditions on such functionals are established to ensure that the Rayleigh-Ritz ground-state densities and the Hohenberg-Kohn ground-state densities are identical. We apply the results to molecular systems in the Born-Oppenheimer approximation. For any given potential v ∈ L(3/2)(ℝ(3)) + L(∞)(ℝ(3)), we establish a one-to-one correspondence between the mixed ground-state densities of the Rayleigh-Ritz variation principle and the mixed ground-state densities of the Hohenberg-Kohn variation principle when the Lieb density-matrix constrained-search universal density functional is taken as the admissible functional. A similar one-to-one correspondence is established between the pure ground-state densities of the Rayleigh-Ritz variation principle and the pure ground-state densities obtained using the Hohenberg-Kohn variation principle with the Levy-Lieb pure-state constrained-search functional. In other words, all physical ground-state densities (pure or mixed) are recovered with these functionals and no false densities (i.e., minimizing densities that are not physical) exist. The importance of topology (i.e., choice of Banach space of densities and potentials) is emphasized and illustrated. The relevance of these results for current-density-functional theory is examined.
Spins and magnetic moments of 58;60;62;64Mn ground states and isomers
Heylen, H; Billowes, J; Bissell, M L; Blaum, K; Campbell, P; Cheal, B; Ruiz, R F Garcia; Geppert, Ch; Gins, W; Kowalska, M; Kreim, K; Lenzi, S M; Moore, I D; Neugart, R; Neyens, G; Nörtershäuser, W; Papuga, J; Yordanov, D T
2015-01-01
The odd-odd 54;56;58;60;62;64Mn isotopes (Z = 25) were studied using bunched-beam collinear laser spectroscopy at ISOLDE, CERN. From the measured hyperfine spectra the spins and magnetic moments of Mn isotopes up to N = 39 were extracted. The previous tentative ground state spin assignments of 58;60;62;64Mn are now firmly determined to be I = 1 along with an I = 4 assignment for the isomeric states in 58;60;62Mn. The I = 1 magnetic moments show a decreasing trend with increasing neutron number while the I = 4 moments remain quite constant between N = 33 and N = 37. The results are compared to large-scale shell-model calculations using the GXPF1A and LNPS effective interactions. The excellent agreement of the ground state moments with the predictions from the LNPS calculations illustrates the need for an increasing amount of proton excitations across Z = 28 and neutron excitations across N = 40 in the ground state wave functions from N = 37 onwards.
CSIR Research Space (South Africa)
de Clercq, L
2010-09-01
Full Text Available Coherent control of the upper vibrational level populations in the electronic ground state of a polyatomic molecule was simulated. Results indicate that selective excitation of a specific upper state level is possible...
CSIR Research Space (South Africa)
De Clercq, L
2010-09-01
Full Text Available Coherent control of the upper vibrational level populations in the electronic ground state of a polyatomic molecule was simulated. Results indicate that selective excitation of a specific upper state level is possible....
Directory of Open Access Journals (Sweden)
Baiyu Liu
2014-01-01
Full Text Available We consider a class of coupled nonlinear Schrödinger systems with potential terms and combined power-type nonlinearities. We establish the existence of ground states, by using a variational method. As an application, some symmetry results for ground states of Schrödinger systems with harmonic potential terms are obtained.
2017-05-01
Dayton, Ohio 45433, United States ‡General Dynamics Information Technology, Dayton, Ohio 45431, United States §Slagle Photonics, Dayton, Ohio 45433...photon spectra result from nonplanar ground- state conformations. Previously studied related chromophores having extended conjugation (Rebane, A...left vertical axis) of the 11 Pt-(R-X)2 compounds in THF studied by the NLT method (left vertical axis). The ground- state extinction spectrum (blue line
Competing ground states of strongly correlated bosons in the Harper-Hofstadter-Mott model
Natu, Stefan S.; Mueller, Erich J.; Das Sarma, S.
2016-06-01
Using an efficient cluster approach, we study the physics of two-dimensional lattice bosons in a strong magnetic field in the regime where the tunneling is much weaker than the on-site interaction strength. We study both the dilute, hard-core bosons at filling factors much smaller than unity occupation per site and the physics in the vicinity of the superfluid-Mott lobes as the density is tuned away from unity. For hard-core bosons, we carry out extensive numerics for a fixed flux per plaquette ϕ =1 /5 and ϕ =1 /3 . At large flux, the lowest-energy state is a strongly correlated superfluid, analogous to He-4, in which the order parameter is dramatically suppressed, but nonzero. At filling factors ν =1 /2 ,1 , we find competing incompressible states which are metastable. These appear to be commensurate density wave states. For small flux, the situation is reversed and the ground state at ν =1 /2 is an incompressible density wave solid. Here, we find a metastable lattice supersolid phase, where superfluidity and density wave order coexist. We then perform careful numerical studies of the physics near the vicinity of the Mott lobes for ϕ =1 /2 and ϕ =1 /4 . At ϕ =1 /2 , the superfluid ground state has commensurate density wave order. At ϕ =1 /4 , incompressible phases appear outside the Mott lobes at densities n =1.125 and n =1.25 , corresponding to filling fractions ν =1 /2 and 1, respectively. These phases, which are absent in single-site mean-field theory, are metastable and have slightly higher energy than the superfluid, but the energy difference between them shrinks rapidly with increasing cluster size, suggestive of an incompressible ground state. We thus explore the interplay between Mott physics, magnetic Landau levels, and superfluidity, finding a rich phase diagram of competing compressible and incompressible states.
Kang, Baotao; Jang, Du-Jeon; Lee, Jin Yong
2015-07-01
Alcohols mediated 7-hydroxyquinoline (7-HQ) complex has received enormous attractions on the issue of proton transfer reaction in the ground and excited states. In the present paper, concentrating on the ground state proton transfer (GSPT), density functional theory (DFT) calculations were carried out to investigate the intrinsic insight into the reaction mechanism. We found that the GSPT is concerted and asynchronous process and can be accelerated by more acidic alcohol. Such GSPT was initiated by the proton transfer from alcohol to keto group of 7-HQ and finished by the proton transfer from nitrogen to alcohol. Our findings were in agreement with experimental conclusions quite well. Our results would be helpful to understand the proton transfer reaction for 7-HQ and related systems.
Towards the measurement of the ground-state hyperfine splitting of antihydrogen
Energy Technology Data Exchange (ETDEWEB)
Juhasz, Bertalan, E-mail: bertalan.juhasz@oeaw.ac.at [Austrian Academy of Sciences, Stefan Meyer Institute for Subatomic Physics (Austria)
2012-12-15
The ASACUSA collaboration at the Antiproton Decelerator of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic beam line, which will consist of a superconducting cusp trap as a source of partially polarized antihydrogen atoms, a radiofrequency spin-flip cavity, a superconducting sextupole magnet as spin analyser, and an antihydrogen detector. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. Monte Carlo simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of better than {approx} 10{sup - 6}. The first preliminary measurements of the hyperfine transitions will start in 2011.
Realization of ground-state artificial skyrmion lattices at room temperature.
Gilbert, Dustin A; Maranville, Brian B; Balk, Andrew L; Kirby, Brian J; Fischer, Peter; Pierce, Daniel T; Unguris, John; Borchers, Julie A; Liu, Kai
2015-10-08
The topological nature of magnetic skyrmions leads to extraordinary properties that provide new insights into fundamental problems of magnetism and exciting potentials for novel magnetic technologies. Prerequisite are systems exhibiting skyrmion lattices at ambient conditions, which have been elusive so far. Here, we demonstrate the realization of artificial Bloch skyrmion lattices over extended areas in their ground state at room temperature by patterning asymmetric magnetic nanodots with controlled circularity on an underlayer with perpendicular magnetic anisotropy (PMA). Polarity is controlled by a tailored magnetic field sequence and demonstrated in magnetometry measurements. The vortex structure is imprinted from the dots into the interfacial region of the underlayer via suppression of the PMA by a critical ion-irradiation step. The imprinted skyrmion lattices are identified directly with polarized neutron reflectometry and confirmed by magnetoresistance measurements. Our results demonstrate an exciting platform to explore room-temperature ground-state skyrmion lattices.
Energy Technology Data Exchange (ETDEWEB)
Kang, Baotao [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Jang, Du-Jeon [Department of Chemistry, Seoul National University, Seoul 151-742 (Korea, Republic of); Lee, Jin Yong, E-mail: jinylee@skku.edu [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)
2015-07-29
Highlights: • Reaction rate constants obtained by DFT agree with experimental ones quite well. • Experimental postulate of concerted and asynchronous GSPT was confirmed. • The GSPT reaction can be decomposed into three asynchronous steps. - Abstract: Alcohols mediated 7-hydroxyquinoline (7-HQ) complex has received enormous attractions on the issue of proton transfer reaction in the ground and excited states. In the present paper, concentrating on the ground state proton transfer (GSPT), density functional theory (DFT) calculations were carried out to investigate the intrinsic insight into the reaction mechanism. We found that the GSPT is concerted and asynchronous process and can be accelerated by more acidic alcohol. Such GSPT was initiated by the proton transfer from alcohol to keto group of 7-HQ and finished by the proton transfer from nitrogen to alcohol. Our findings were in agreement with experimental conclusions quite well. Our results would be helpful to understand the proton transfer reaction for 7-HQ and related systems.
Theoretical study on the ground electronic state of FO(+) and FO(-).
Li, Song; Zheng, Rui; Chen, Shan-Jun; Zhu, De-Sheng; Fan, Qun-Chao
2014-12-10
The equilibrium structures of the ground electronic states for molecular ions FO(+) and FO(-) have been calculated by using the multi-reference configuration interaction method in combination with the augmented correlation-consistent basis sets up through sextuple zeta quality. The equilibrium parameters, potential energy curves and spectroscopic constants are derived for both species. The extrapolation schemes are adopted to estimate the complete basis set limit. The corrections of core-valence correlation and relativistic effect are included to improve the accuracy of the calculations. The vibrational energy levels as well as rotational and centrifugal distortion constants of the ground electronic states for both systems are obtained by solving the radial Schrödinger equation of nuclear motion. The computations on neutral FO radical are also carried out to investigate the ionization potentials and the electron affinities. Copyright © 2014 Elsevier B.V. All rights reserved.
Application of Stochastic variational method with correlated Ground States to coulombic systems
Energy Technology Data Exchange (ETDEWEB)
Usukura, Junko; Suzuki, Yasuyuki [Niigata Univ. (Japan); Varga, K.
1998-07-01
Positronium molecule, Ps{sub 2} has not been found experimentally yet, and it has been believed theoretically that Ps{sub 2} has only one bound state with L = 0. We predicted the existence of new bound state of Ps{sub 2}, which is the excited state with L = 1 and comes from Pauli principle, by Stochastic variational method. There are two decay mode with respect to Ps{sub 2}(P); one is pair annihilation and another is electric dipole (E1) transition to the ground state. While it is difficult to tell {gamma}-ray caused by annihilation of Ps{sub 2} from that of Ps since both of them have same energy, Energy (4.94 eV) of the photon emitted in E1 transition is specific enough to distinguish from other spectra. Then the excited state is one of clues to observe Ps{sub 2}. (author)
Properties of Heavy Fermion in an Impurity Anderson Model with f2 Local Singlet Ground State
Shiina, Ryousuke
2018-01-01
The Fermi-liquid properties of a two-orbital impurity Anderson model with an f2 local singlet ground state is studied by the numerical renormalization group method. It is shown that a heavy-fermion (HF) state with a vanishingly small Wilson ratio is realized in the vicinity of the quantum critical point (QCP) between the local-singlet and Kondo-singlet phases. The parameter area in which the HF behavior appears is remarkably enlarged with increasing the excitation energy from the local singlet to triplet states. It is also clarified that the HF state takes place with an intermediate average occupancy of f electrons, reflecting the existence of the QCP under strong valence fluctuation. The possible application of these theoretical results to an unconventional HF state in Sm compounds is discussed.
Ground state study of the thin ferromagnetic nano-islands for artificial spin ice arrays
Energy Technology Data Exchange (ETDEWEB)
Vieira Júnior, D. S., E-mail: damiao.vieira@ifsudestemg.edu.br [Departamento Acadêmico de Matemática, Física e Estatística, Instituto Federal de Educação, Ciência e Tecnologia do Sudeste de Minas Gerais - Câmpus Rio Pomba, Rio Pomba, Minas Gerais 36180-000 (Brazil); Departamento de Física, Laboratório de Simulação Computacional, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais 36036-330 (Brazil); Leonel, S. A., E-mail: sidiney@fisica.ufjf.br; Dias, R. A., E-mail: radias@fisica.ufjf.br; Toscano, D., E-mail: danilotoscano@fisica.ufjf.br; Coura, P. Z., E-mail: pablo@fisica.ufjf.br; Sato, F., E-mail: sjfsato@fisica.ufjf.br [Departamento de Física, Laboratório de Simulação Computacional, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais 36036-330 (Brazil)
2014-09-07
In this work, we used numerical simulations to study the magnetic ground state of the thin elongated (elliptical) ferromagnetic nano-islands made of Permalloy. In these systems, the effects of demagnetization of dipolar source generate a strong magnetic anisotropy due to particle shape, defining two fundamental magnetic ground state configurations—vortex or type C. To describe the system, we considered a model Hamiltonian in which the magnetic moments interact through exchange and dipolar potentials. We studied the competition between the vortex states and aligned states—type C—as a function of the shape of each elliptical nano-islands and constructed a phase diagram vortex—type C state. Our results show that it is possible to obtain the elongated nano-islands in the C-state with aspect ratios less than 2, which is interesting from the technological point of view because it will be possible to use smaller islands in spin ice arrays. Generally, the experimental spin ice arrangements are made with quite elongated particles with aspect ratio approximately 3 to ensure the C-state.
Ground state and orbital stability for the NLS equation on a general starlike graph with potentials
Cacciapuoti, Claudio; Finco, Domenico; Noja, Diego
2017-08-01
We consider a nonlinear Schrödinger equation (NLS) posed on a graph (or network) composed of a generic compact part to which a finite number of half-lines are attached. We call this structure a starlike graph. At the vertices of the graph interactions of δ-type can be present and an overall external potential is admitted. Under general assumptions on the potential, we prove that the NLS is globally well-posed in the energy domain. We are interested in minimizing the energy of the system on the manifold of constant mass (L 2-norm). When existing, the minimizer is called ground state and it is the profile of an orbitally stable standing wave for the NLS evolution. We prove that a ground state exists for sufficiently small masses whenever the quadratic part of the energy admits a simple isolated eigenvalue at the bottom of the spectrum (the linear ground state). This is a wide generalization of a result previously obtained for a star-graph with a single vertex. The main part of the proof is devoted to prove the concentration compactness principle for starlike structures; this is non trivial due to the lack of translation invariance of the domain. Then we show that a minimizing, bounded, H 1 sequence for the constrained NLS energy with external linear potentials is in fact convergent if its mass is small enough. Moreover we show that the ground state bifurcates from the vanishing solution at the bottom of the linear spectrum. Examples are provided with a discussion of the hypotheses on the linear part.
Directory of Open Access Journals (Sweden)
Xia Liu
2017-02-01
Full Text Available The discrete nonlinear Schrodinger equation is a nonlinear lattice system that appears in many areas of physics such as nonlinear optics, biomolecular chains and Bose-Einstein condensates. In this article, we consider a class of discrete nonlinear Schrodinger equations with unbounded potentials. We obtain some new sufficient conditions on the multiplicity results of ground state solutions for the equations by using the symmetric mountain pass lemma. Recent results in the literature are greatly improved.
Eniade, Abiodun Adeyemi; Bello-Olusoji, A. Oluayo
2011-01-01
In situ ecological assessment of the breeding grounds of palaemonid prawns was conducted in some selected locations around Ondo state coastal area between the months of April and September. Data obtained were subjected to both descriptive and inferential statistics. Three species of Palaemonid prawns were identified in four different locations within the study area with relative abundance ratio of 4:3:1. Macrobrachium macrobrachion, Nematopalaemon hastatus and Palaemon maculatus respectively....
Resolution of nuclear ground and isomeric states by a Penning trap mass spectrometer
Energy Technology Data Exchange (ETDEWEB)
Bollen, G.; Kluge, H.; Koenig, M.; Otto, T.; Savard, G.; Stolzenberg, H. (Institut fuer Physik, Universitaet Mainz, D-6500 Mainz (Germany)); Moore, R.B.; Rouleau, G. (Foster Radiation Laboratory, McGill University, Montreal, Province du Quebec, H3A 2B2 (Canada)); Audi, G. (ISOLDE Collaboration CERN, PPE-Division, CH-1211 Geneva (Switzerland))
1992-12-01
Ground and isomeric states of a nucleus have been resolved for the first time by mass spectrometry. Measurements on [sup 78]Rb[sup [ital m],][ital g] and [sup 84]Rb[sup [ital m],][ital g] were performed using a tandem Penning trap mass spectrometer on-line with the isotope separator ISOLDE/CERN. The effects of ion-ion interaction were investigated for two ion species differing in mass and stored simultaneously in the trap.
Resolution of nuclear ground and isomeric states by a Penning trap mass spectrometer
Bollen, G.; Kluge, H.-J.; König, M.; Otto, T.; Savard, G.; Stolzenberg, H.; Moore, R. B.; Rouleau, G.; Audi, G.; ISOLDE Collaboration
1992-12-01
Ground and isomeric states of a nucleus have been resolved for the first time by mass spectrometry. Measurements on 78Rbm,g and 84Rbm,g were performed using a tandem Penning trap mass spectrometer on-line with the isotope separator ISOLDE/CERN. The effects of ion-ion interaction were investigated for two ion species differing in mass and stored simultaneously in the trap.
Analytical approach to the helium-atom ground state using correlated wavefunctions
Energy Technology Data Exchange (ETDEWEB)
Bhattacharyya, S.; Bhattacharyya, A.; Talukdar, B. [Visvabharati Univ., Santiniketan (India). Dept. of Physics; Deb, N.C. [Indian Association for the Cultivation of Science, Calcutta (India). Dept. of Theoretical Physics
1996-03-14
A realistic three-parameter correlated wavefunction is used to construct an exact analytical expression for the expectation value of the helium-atom Hamiltonian expressed in the interparticle coordinates. The parameters determined variationally are found to satisfy the orbital and correlation cusp conditions to a fair degree of accuracy and yield a value for the ground-state energy which is in good agreement with the exact result. (author).
Stable π-Extended p -Quinodimethanes: Synthesis and Tunable Ground States
Zeng, Zebing
2014-12-18
© 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. p-Quinodimethane (p-QDM) is a highly reactive hydrocarbon showing large biradical character in the ground state. It has been demonstrated that incorporation of the p-QDM moiety into an aromatic hydrocarbon framework could lead to new π-conjugated systems with significant biradical character and unique optical, electronic and magnetic properties. On the other hand, the extension of p-QDM is expected to result in molecules with even larger biradical character and higher reactivity. Therefore, the synthesis of stable π-extended p-QDMs is very challenging. In this Personal Account we will briefly discuss different stabilizing strategies and synthetic methods towards stable π-extended p-QDMs with tunable ground states and physical properties, including two types of polycyclic hydrocarbons: (1) tetrabenzo-Tschitschibabin\\'s hydrocarbons, and (2) tetracyano-rylenequinodimethanes. We will discuss how the aromaticity, substituents and steric hindrance play important roles in determining their ground states and properties. Incorporation of the p-quinodimethane moiety into aromatic hydrocarbon frameworks can lead to new π-conjugated systems with significant biradical character and unique optical, electronic and magnetic properties. Furthermore, the extension of p-QDM is expected to result in molecules with even larger biradical character and higher reactivity. In this Personal Account, different stabilizing strategies and synthetic methods towards stable π-extended p-QDMs with tunable ground states and physical properties are briefly discussed, including the roles of aromaticity, substituents and steric hindrance.
Anomalous Ground State of the Electrons in Nano-confined Water
2016-06-13
using x-ray Compton scattering and a computational model, that the ground state configuration of the valence electrons in a particular nano...version of Nafion), were the same as those used in the neutron Compton scattering measurements4. The two samples have very different conductivities at the...was 14, the same as was used in the neutron experiments. The samples were sealed in the x-ray sample cells while in contact with the vapor to avoid
Ground State of the Universe and the Cosmological Constant. A Nonperturbative Analysis.
Husain, Viqar; Qureshi, Babar
2016-02-12
The physical Hamiltonian of a gravity-matter system depends on the choice of time, with the vacuum naturally identified as its ground state. We study the expanding Universe with scalar field in the volume time gauge. We show that the vacuum energy density computed from the resulting Hamiltonian is a nonlinear function of the cosmological constant and time. This result provides a new perspective on the relation between time, the cosmological constant, and vacuum energy.
Radiative Decay Widths of Ground and Excited States of Vector Charmonium and Bottomonium
Directory of Open Access Journals (Sweden)
Hluf Negash
2017-01-01
Full Text Available We study the radiative decay widths of vector quarkonia for the process of J/ψ(nS→ηc(nSγ and Υ(nS→ηb(nSγ (for principal quantum numbers n=1,2,3 in the framework of Bethe-Salpeter equation under the covariant instantaneous ansatz using a 4×4 form of BSE. The parameters of the framework were determined by a fit to the mass spectrum of ground states of pseudoscalar and vector quarkonia, such as ηc, ηb, J/ψ, and Υ. These input parameters so fixed were found to give good agreements with data on mass spectra of ground and excited states of pseudoscalar and vector quarkonia, leptonic decay constants of pseudoscalar and vector quarkonia, two-photon decays, and two-gluon decays of pseudoscalar quarkonia in our recent paper. With these input parameters so fixed, the radiative decay widths of ground (1S and excited (2S,3S states of heavy vector quarkonia (J/Ψ and Υ are calculated and found to be in reasonable agreement with data.
Schreck, Simon; Pietzsch, Annette; Kennedy, Brian; Såthe, Conny; Miedema, Piter S; Techert, Simone; Strocov, Vladimir N; Schmitt, Thorsten; Hennies, Franz; Rubensson, Jan-Erik; Föhlisch, Alexander
2016-01-29
Thermally driven chemistry as well as materials' functionality are determined by the potential energy surface of a systems electronic ground state. This makes the potential energy surface a central and powerful concept in physics, chemistry and materials science. However, direct experimental access to the potential energy surface locally around atomic centers and to its long-range structure are lacking. Here we demonstrate how sub-natural linewidth resonant inelastic soft x-ray scattering at vibrational resolution is utilized to determine ground state potential energy surfaces locally and detect long-range changes of the potentials that are driven by local modifications. We show how the general concept is applicable not only to small isolated molecules such as O2 but also to strongly interacting systems such as the hydrogen bond network in liquid water. The weak perturbation to the potential energy surface through hydrogen bonding is observed as a trend towards softening of the ground state potential around the coordinating atom. The instrumental developments in high resolution resonant inelastic soft x-ray scattering are currently accelerating and will enable broad application of the presented approach. With this multidimensional potential energy surfaces that characterize collective phenomena such as (bio)molecular function or high-temperature superconductivity will become accessible in near future.
Ground beetles (Coleoptera, Carabidae of the Hanford Nuclear Site in south-central Washington State
Directory of Open Access Journals (Sweden)
Chris Looney
2014-04-01
Full Text Available In this paper we report on ground beetles (Coleoptera: Carabidae collected from the Hanford Nuclear Reservation and Hanford National Monument (together the Hanford Site, which is located in south-central Washington State. The Site is a relatively undisturbed relict of the shrub-steppe habitat present throughout much of the western Columbia Basin before the westward expansion of the United States. Species, localities, months of capture, and capture method are reported for field work conducted between 1994 and 2002. Most species were collected using pitfall traps, although other capture methods were employed. Trapping results indicate the Hanford Site supports a diverse ground beetle community, with over 90% of the 92 species captured native to North America. Four species collected during the study period are newly recorded for Washington State: Bembidion diligens Casey, Calosoma obsoletum Say, Pseudaptinus rufulus (LeConte, and Stenolophus lineola (Fabricius. Based on these data, the Site maintains a diverse ground beetle fauna and, due to its size and diversity of habitats, is an important repository of shrub-steppe biodiversity.
DEFF Research Database (Denmark)
Johnsen, Kristinn; Yngvason, Jakob
1996-01-01
We report on a numerical study of the density matrix functional introduced by Lieb, Solovej, and Yngvason for the investigation of heavy atoms in high magnetic fields. This functional describes exactly the quantum mechanical ground state of atoms and ions in the limit when the nuclear charge Z...... and the electron number N tend to infinity with N/Z fixed, and the magnetic field B tends to infinity in such a way that B/Z4/3→∞. We have calculated electronic density profiles and ground-state energies for values of the parameters that prevail on neutron star surfaces and compared them with results obtained...... by other methods. For iron at B=1012 G the ground-state energy differs by less than 2% from the Hartree-Fock value. We have also studied the maximal negative ionization of heavy atoms in this model at various field strengths. In contrast to Thomas-Fermi type theories atoms can bind excess negative charge...
Energy Technology Data Exchange (ETDEWEB)
Meissner, Thomas
2013-05-13
In the present work, a novel probe design for high pressure NMR experiments in gem anvil cells (GAC) was used which places a small microcoil inside the high pressure volume as the detection coil. Based on tests carried out at ambient pressure and high pressure of 42 kbar it is demonstrated that this approach is indeed feasible and results in an increase of sensitivity by two orders of magnitude compared to previous GAC-NMR designs. The design was then successfully employed in the investigation of the electronic properties of metallic aluminum and the high temperature superconductor YBa{sub 2}Cu{sub 4}O{sub 8} at pressures of up to 101 kbar. Because of its improved sensitivity and the potential to achieve even higher pressures, the microcoil GAC-NMR setup should prove useful in the investigation of materials under high pressure conditions in the future. In the case of metallic aluminum, the effect of pressure on the electronic density of states at the Fermi level was probed via the Knight-shift K and the spin-lattice relaxation time T{sub 1} at room temperature up to a pressure of 101 kbar, extending the pressure range of previous NMR measurements by a factor of 14 [72]. Most notably, a decrease of K(p) by 11% is detected in the investigated pressure range that is inconsistent with a free electron behavior of the density of states. Numerical band structure calculations that are in excellent agreement with the experimental data suggest that the observed changes of K and T{sub 1} are due to a kink in the electronic states at a Lifshitz-transition at about 75 kbar which has not been observed previously. A further decrease of K by a factor of 2 is predicted to occur in the pressure range up to 300 kbar. In addition, an increase of the NMR linewidths of the metallic aluminum signal was observed above about 42 kbar that is inconsistent with a pure dipolar linewidth. Based on an analysis of the field dependence of this effect it was ascribed to a small additional
Fujita, Kazuhiro; Schmidt, Andrew R.; Kim, Eun-Ah; Lawler, Michael J.; Lee, Dung Hai; Davis, J. C.; Eisaki, Hiroshi; Uchida, Shin-ichi
2012-01-01
One of the key motivations for the development of atomically resolved spectroscopic imaging scanning tunneling microscopy (SI-STM) has been to probe the electronic structure of cuprate high temperature superconductors. In both the d-wave superconducting (dSC) and the pseudogap (PG) phases of underdoped cuprates, two distinct classes of electronic states are observed using SI-STM. The first class consists of the dispersive Bogoliubov quasiparticles of a homogeneous d-wave superconductor. These are detected below a lower energy scale |E|=Δ0 and only upon a momentum space (k-space) arc which terminates near the lines connecting k=±(π/a0,0) to k=±(0,π/a0). Below optimal doping, this ``nodal'' arc shrinks continuously with decreasing hole density. In both the dSC and PG phases, the only broken symmetries detected in the |E|≤Δ0 states are those of a d-wave superconductor. The second class of states occurs at energies near the pseudogap energy scale |E|˜ Δ1 which is associated conventionally with the ``antinodal'' states near k=±(π/a0,0) and k=±(0,π/a0). We find that these states break the expected 90°-rotational (C4) symmetry of electronic structure within CuO2 unit cells, at least down to 180°-rotational (C2) symmetry (nematic) but in a spatially disordered fashion. This intra-unit-cell C4 symmetry breaking coexists at |E|˜Δ1 with incommensurate conductance modulations locally breaking both rotational and translational symmetries (smectic). The characteristic wavevector Q of the latter is determined, empirically, by the k-space points where Bogoliubov quasiparticle interference terminates, and therefore evolves continuously with doping. The properties of these two classes of |E|˜Δ1 states are indistinguishable in the dSC and PG phases. To explain this segregation of k-space into the two regimes distinguished by the symmetries of their electronic states and their energy scales |E|˜Δ1 and |E|≤Δ0, and to understand how this impacts the electronic
The fine structure levels for ground states of negative ions of nitrogen and phosphorus
Directory of Open Access Journals (Sweden)
Leyla Özdemir
2013-01-01
Full Text Available The fine structure levels for negative ions (anions of nitrogen and phosphorus have been investigated using multiconfiguration Hartree-Fock method within the framework of Breit-Pauli Hamiltonian (MCHF+BP. Nitrogen and phosphorus have half-filled outer shell in ground state 1s22s22p3 4S and 1s22s22p33s23p3 4S, respectively. It has been stated in most works that the negative ion of nitrogen is instable whereas the negative ion of phosphorus is stable. The results obtained have been compared with other works.
Ground-state properties of the two-site Hubbard-Holstein model: an exact solution
Energy Technology Data Exchange (ETDEWEB)
Zhang Yuyu; Wang Xiaoguang [Department of Physics, Zhejiang University, Hangzhou 321004 (China); Liu Tao; Wang Kelin [Department of Physics, Southwest University of Science and Technology, Mianyang 621010 (China); Chen Qinghu, E-mail: qhchen@zju.edu.c [Center for Statistical and Theoretical Condensed Matter Physics, Zhejiang Normal University, Jinhua 321004 (China)
2009-10-14
We study the two-site Hubbard-Holstein model by using an extended phonon coherent state. For the nontrivial singlet bipolarons, the double occupancy probability, the fidelity and the entanglement entropy are calculated to characterize the ground-state properties in both two-site and single-site bipolaron-dominated regimes. We use the localized minimum of the fidelity to define a crossover and plot the bipolaron phase diagram, which separates the large and small entanglement region. Furthermore, the relation between the bipolaron entanglement and the correlation functions demonstrates that the large entanglement corresponds to the large magnitude of lattice deformations induced by electrons.
Lee, Kyuhyun; Youn, Yong; Han, Seungwu
2017-01-01
We identify ground-state collinear spin ordering in various antiferromagnetic transition metal oxides by constructing the Ising model from first-principles results and applying a genetic algorithm to find its minimum energy state. The present method can correctly reproduce the ground state of well-known antiferromagnetic oxides such as NiO, Fe2O3, Cr2O3 and MnO2. Furthermore, we identify the ground-state spin ordering in more complicated materials such as Mn3O4 and CoCr2O4.
Stability and Symmetry-Breaking Bifurcation for the Ground States of a NLS with a δ' Interaction
Adami, Riccardo; Noja, Diego
2013-02-01
We determine and study the ground states of a focusing Schrödinger equation in dimension one with a power nonlinearity | ψ|2 μ ψ and a strong inhomogeneity represented by a singular point perturbation, the so-called (attractive) δ' interaction, located at the origin. The time-dependent problem turns out to be globally well posed in the subcritical regime, and locally well posed in the supercritical and critical regime in the appropriate energy space. The set of the (nonlinear) ground states is completely determined. For any value of the nonlinearity power, it exhibits a symmetry breaking bifurcation structure as a function of the frequency (i.e., the nonlinear eigenvalue) ω. More precisely, there exists a critical value ω* of the nonlinear eigenvalue ω, such that: if ω0 ground state and it is an odd function; if ω > ω* then there exist two non-symmetric ground states. We prove that before bifurcation (i.e., for ω ground state is orbitally stable. After bifurcation (ω = ω* + 0), ground states are stable if μ does not exceed a value {μ^star} that lies between 2 and 2.5, and become unstable for μ > μ*. Finally, for μ > 2 and {ω ≫ ω^*}, all ground states are unstable. The branch of odd ground states for ω ω*, obtaining a family of orbitally unstable stationary states. Existence of ground states is proved by variational techniques, and the stability properties of stationary states are investigated by means of the Grillakis-Shatah-Strauss framework, where some non-standard techniques have to be used to establish the needed properties of linearization operators.
Modified Magnetic Ground State in Nimn (2) O (4) Thin Films
Energy Technology Data Exchange (ETDEWEB)
Nelson-Cheeseman, B.B.; Chopdekar, R.V.; Iwata, J.M.; Toney, M.F.; Arenholz, E.; Suzuki, Y.; /SLAC
2012-08-23
The authors demonstrate the stabilization of a magnetic ground state in epitaxial NiMn{sub 2}O{sub 4} (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and epitaxial strain are ruled out as possible causes for the new magnetic ground state in the as-grown films. However, a decrease in the octahedral Mn{sup 4+}:Mn{sup 3+} concentration is observed and likely disrupts the double exchange that produces the magnetic state at intermediate temperatures. X-ray magnetic circular dichroism and bulk magnetometry indicate a canted ferrimagnetic state in all samples at low T. Together these results suggest that the collinear ferrimagnetic state observed in bulk NMO at intermediate temperatures is suppressed in the as grown NMO thin films due to a decrease in octahedral Mn{sup 4+}, while the canted moment ferrimagnetic ordering is preserved below 60 K.
Modified magnetic ground state in NiMn2O4 thin films
Energy Technology Data Exchange (ETDEWEB)
Nelson-Cheeseman, B. B.; Chopdekar, R. V.; Toney, M. F.; Arenholz, E.; Suzuki, Y.; Iwata, J.M.
2010-08-03
We demonstrate the stabilization of a magnetic ground state in epitaxial NiMn2O4 (NMO) thin films not observed in their bulk counterpart. Bulk NMO exhibits a magnetic transition from a paramagnetic phase to a collinear ferrimagnetic moment configuration below 110 K and to a canted moment configuration below 70 K. By contrast, as-grown NMO films exhibit a single magnetic transition at 60 K and annealed films exhibit the magnetic behavior found in bulk. Cation inversion and epitaxial strain are ruled out as possible causes for the new magnetic ground state in the as-grown films. However, a decrease in the octahedral Mn{sup 4+}:Mn{sup 3+} concentration is observed and likely disrupts the double exchange that produces the magnetic state at intermediate temperatures. X-ray magnetic circular dichroism and bulk magnetometry indicate a canted ferrimagnetic state in all samples at low temperature. Together these results suggest that the collinear ferrimagnetic state observed in bulk NMO at intermediate temperatures is suppressed in the as grown NMO thin films due to a decrease in octahedral Mn{sup 4+} while the canted moment ferrimagnetic ordering is preserved below 60 K.
Augustyns, V.; van Stiphout, K.; Joly, V.; Lima, T. A. L.; Lippertz, G.; Trekels, M.; Menéndez, E.; Kremer, F.; Wahl, U.; Costa, A. R. G.; Correia, J. G.; Banerjee, D.; Gunnlaugsson, H. P.; von Bardeleben, J.; Vickridge, I.; Van Bael, M. J.; Hadermann, J.; Araújo, J. P.; Temst, K.; Vantomme, A.; Pereira, L. M. C.
2017-11-01
γ -Fe and related alloys are model systems of the coupling between structure and magnetism in solids. Since different electronic states (with different volumes and magnetic ordering states) are closely spaced in energy, small perturbations can alter which one is the actual ground state. Here, we demonstrate that the ferromagnetic state of γ -Fe nanoparticles is associated with a tetragonal distortion of the fcc structure. Combining a wide range of complementary experimental techniques, including low-temperature Mössbauer spectroscopy, advanced transmission electron microscopy, and synchrotron radiation techniques, we unambiguously identify the tetragonally distorted ferromagnetic ground state, with lattice parameters a =3.76 (2 )Å and c =3.50 (2 )Å , and a magnetic moment of 2.45(5) μB per Fe atom. Our findings indicate that the ferromagnetic order in nanostructured γ -Fe is generally associated with a tetragonal distortion. This observation motivates a theoretical reassessment of the electronic structure of γ -Fe taking tetragonal distortion into account.
Leigh, Katherine N; Webster, Charles Edwin
2014-02-28
The mechanisms of phosphoryl transfer enzymes have garnered considerable attention. Cyclic AMP-dependent protein kinase (cAPK) catalyzes the transfer of the γ phosphoryl group of ATP to the serine hydroxyl group of a peptide chain. Metal-containing fluoro species have been used as transition-state and ground-state analogues in a variety of phosphoryl transfer enzymes and have shed light on the nature of the requirements in the active site to catalyze phosphoryl transfer. For cAPK, we present computational studies of the mechanism of phosphoryl transfer and the structure and (19)F NMR spectra of various ground- (BeF3(-)) and transition-state (MgF3(-), AlF4(-), and AlF3(0)) analogues. With native substrate, the phosphoryl transfer proceeds through a five-coordinate phosphorane transition state, i.e., there is not a five-coordinate phosphorane intermediate. Comparisons of simulated and experimental (19)F NMR spectra show cAPK prefers a monoanionic analogue (MgF3(-) or AlF4(-)) over a neutral analogue (AlF3), supporting the charge balance hypothesis.
Studies of photoionization processes from ground-state and excited-state atoms and molecules
Energy Technology Data Exchange (ETDEWEB)
Ederer, D.L.; Parr, A.C.; West, J.B.
1982-01-01
Recent triply-differential photoelectron spectroscopy experiments designed for the study of correlation effects in atoms and molecules are described. Final-state symmetry of the n=2 state of helium has been determined. The non-Franck-Condon behavior of vibrational branching ratios and large variations of the angular asymmetry parameter has been observed for shape resonances and autoionizing resonances in CO and other molecules. Recent observations of the photoionization of excited sodium atoms are also described.
Multiplet of skyrmion states on a curvilinear defect: skyrmion lattices as a ground state
Kravchuk, Volodymyr P.; Sheka, Denis D.; Volkov, Oleksii M.; Rößler, Ulrich K.; Brink, Jeroen van den; Makarov, Denys; Gaididei, Yuri
2017-01-01
We show that the presence of a localized curvilinear defect drastically changes magnetic properties of a thin perpendicularly magnetized ferromagnetic film. For a large enough defect amplitude a discrete set of equilibrium magnetization states appears forming a ladder of energy levels. Each equilibrium state has either zero or unit topological charge, i.e. topologically trivial and skyrmion multiplets generally appear. Transitions between the levels with the same topological charge are allowe...
Directory of Open Access Journals (Sweden)
Y. Sajeev
2015-08-01
Full Text Available The equation-of-motion coupled cluster (EOMCC method based on the excited state Hartree-Fock (ESHF solutions is shown to be appropriate for computing the entire ground state potential energy curves of strongly correlated higher-order bonds. The new approach is best illustrated for the homolytic dissociation of higher-order bonds in molecules. The required multireference character of the true ground state wavefunction is introduced through the linear excitation operator of the EOMCC method. Even at the singles and doubles level of cluster excitation truncation, the nonparallelity error of the ground state potential energy curve from the ESHF based EOMCC method is small.
Egorova, Dassia
2015-06-01
Several recent experiments report on possibility of dark-state detection by means of so called beating maps of two-dimensional photon-echo spectroscopy [Ostroumov et al., Science 340, 52 (2013); Bakulin et al., Ultrafast Phenomena XIX (Springer International Publishing, 2015)]. The main idea of this detection scheme is to use coherence induced upon the laser excitation as a very sensitive probe. In this study, we investigate the performance of ground-state coherence in the detection of dark electronic states. For this purpose, we simulate beating maps of several models where the excited-state coherence can be hardly detected and is assumed not to contribute to the beating maps. The models represent strongly coupled electron-nuclear dynamics involving avoided crossings and conical intersections. In all the models, the initially populated optically accessible excited state decays to a lower-lying dark state within few hundreds femtoseconds. We address the role of Raman modes and of interstate-coupling nature. Our findings suggest that the presence of low-frequency Raman active modes significantly increases the chances for detection of dark states populated via avoided crossings, whereas conical intersections represent a more challenging task.
Ground state selection under pressure in the quantum pyrochlore magnet Yb2Ti2O7.
Kermarrec, E; Gaudet, J; Fritsch, K; Khasanov, R; Guguchia, Z; Ritter, C; Ross, K A; Dabkowska, H A; Gaulin, B D
2017-03-15
A quantum spin liquid is a state of matter characterized by quantum entanglement and the absence of any broken symmetry. In condensed matter, the frustrated rare-earth pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7, so-called spin ices, exhibit a classical spin liquid state with fractionalized thermal excitations (magnetic monopoles). Evidence for a quantum spin ice, in which the magnetic monopoles become long range entangled and an emergent quantum electrodynamics arises, seems within reach. The magnetic properties of the quantum spin ice candidate Yb2Ti2O7 have eluded a global understanding and even the presence or absence of static magnetic order at low temperatures is controversial. Here we show that sensitivity to pressure is the missing key to the low temperature behaviour of Yb2Ti2O7. By combining neutron diffraction and muon spin relaxation on a stoichiometric sample under pressure, we evidence a magnetic transition from a disordered, non-magnetic, ground state to a splayed ferromagnetic ground state.
Ground state selection under pressure in the quantum pyrochlore magnet Yb2Ti2O7
Kermarrec, E.; Gaudet, J.; Fritsch, K.; Khasanov, R.; Guguchia, Z.; Ritter, C.; Ross, K. A.; Dabkowska, H. A.; Gaulin, B. D.
2017-01-01
A quantum spin liquid is a state of matter characterized by quantum entanglement and the absence of any broken symmetry. In condensed matter, the frustrated rare-earth pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7, so-called spin ices, exhibit a classical spin liquid state with fractionalized thermal excitations (magnetic monopoles). Evidence for a quantum spin ice, in which the magnetic monopoles become long range entangled and an emergent quantum electrodynamics arises, seems within reach. The magnetic properties of the quantum spin ice candidate Yb2Ti2O7 have eluded a global understanding and even the presence or absence of static magnetic order at low temperatures is controversial. Here we show that sensitivity to pressure is the missing key to the low temperature behaviour of Yb2Ti2O7. By combining neutron diffraction and muon spin relaxation on a stoichiometric sample under pressure, we evidence a magnetic transition from a disordered, non-magnetic, ground state to a splayed ferromagnetic ground state. PMID:28294118
Magnetism in single crystal Ce{sub 2}Fe{sub 17} with two types of magnetic ground states
Energy Technology Data Exchange (ETDEWEB)
Makihara, Y. E-mail: makihara@kyukyo-u.ac.jp; Uwatoko, Y.; Matsuoka, H.; Kosaka, M.; Fukuda, H.; Fujii, H
2004-05-01
Magnetization and neutron diffraction measurements have been performed on two Ce{sub 2}Fe{sub 17} single crystals that have different magnetic ground states. Two types of magnetic structure in the ground states for Ce{sub 2}Fe{sub 17} are confirmed. From the above results, it is deduced that the hybridization between the Fe 3d- and Ce 4f-electrons plays an important role on the magnetism of Ce{sub 2}Fe{sub 17} in the ground states.
Extraction of ground-state decay constant from dispersive sum rules: QCD vs potential models
Energy Technology Data Exchange (ETDEWEB)
Lucha, Wolfgang [HEPHY, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna (Austria); Melikhov, Dmitri, E-mail: dmitri_melikhov@gmx.d [HEPHY, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna (Austria); Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria); SINP, Moscow State University, 119991 Moscow (Russian Federation); Simula, Silvano [INFN, Sezione di Roma III, Via della Vasca Navale 84, I-00146 Roma (Italy)
2010-04-05
We compare the extraction of the ground-state decay constant from the two-point correlator in QCD and in potential models and show that the results obtained at each step of the extraction procedure follow a very similar pattern. We prove that allowing for a Borel-parameter-dependent effective continuum threshold yields two essential improvements compared to employing a Borel-parameter-independent quantity: (i) It reduces considerably the (unphysical) dependence of the extracted bound-state mass and the decay constant on the Borel parameter. (ii) In a potential model, where the actual value of the decay constant is known from the Schroedinger equation, a Borel-parameter-dependent threshold leads to an improvement of the accuracy of the extraction procedure. Our findings suggest that in QCD a Borel-parameter-dependent threshold leads to a more reliable and accurate determination of bound-state characteristics by the method of sum rules.
Frozen Gaussian Wavepacket Study of the Ground State of the He Atom.
Wang, Ling; Pollak, Eli
2007-03-01
The Rayleigh-Ritz functional is used in conjunction with an approximate time evolution to improve ab initio estimates of ground-state energies. The improvement is due in part to the introduction of a novel variational "normalization function" for the approximate propagator. An additional variational parameter was introduced in the form of a constant shift energy of the Hamiltonian. The approximate propagator used was the frozen Gaussian propagator; however, the trajectories evolved on the coherent-state averaged Hamiltonian (Q representation). For Coulombic forces, this removes the singularity, easing the computation. An additional variational parameter was the width parameter used for the coherent states appearing in the frozen Gaussian propagator. Using an initial combination of nine Gaussian functions for He, with an initial energy of -2.5115 au, the variational method, with a very short time interval of integration, led to an improved energy of -2.81 ± 0.04 au.
Ground State Geometries of Polyacetylene Chains from Many-Particle Quantum Mechanics.
Barborini, Matteo; Guidoni, Leonardo
2015-09-08
Due to the crucial role played by electron correlation, the accurate determination of ground state geometries of π-conjugated molecules is still a challenge for many quantum chemistry methods. Because of the high parallelism of the algorithms and their explicit treatment of electron correlation effects, Quantum Monte Carlo calculations can offer an accurate and reliable description of the electronic states and of the geometries of such systems, competing with traditional quantum chemistry approaches. Here, we report the structural properties of polyacetylene chains H-(C₂H₂)(N)-H up to N = 12 acetylene units, by means of Variational Monte Carlo (VMC) calculations based on the multi-determinant Jastrow Antisymmetrized Geminal Power (JAGP) wave function. This compact ansatz can provide for such systems an accurate description of the dynamical electronic correlation as recently detailed for the 1,3-butadiene molecule [J. Chem. Theory Comput. 2015 11 (2), 508-517]. The calculated Bond Length Alternation (BLA), namely the difference between the single and double carbon bonds, extrapolates, for N → ∞, to a value of 0.0910(7) Å, compatible with the experimental data. An accurate analysis was able to distinguish between the influence of the multi-determinantal AGP expansion and of the Jastrow factor on the geometrical properties of the fragments. Our size-extensive and self-interaction-free results provide new and accurate ab initio references for the structures of the ground state of polyenes.
Looney, Chris; Zack, Richard S; Labonte, James R
2014-01-01
Carabidae) collected from the Hanford Nuclear Reservation and Hanford National Monument (together the Hanford Site), which is located in south-central Washington State. The Site is a relatively undisturbed relict of the shrub-steppe habitat present throughout much of the western Columbia Basin before the westward expansion of the United States. Species, localities, months of capture, and capture method are reported for field work conducted between 1994 and 2002. Most species were collected using pitfall traps, although other capture methods were employed. Trapping results indicate the Hanford Site supports a diverse ground beetle community, with over 90% of the 92 species captured native to North America. Four species collected during the study period are newly recorded for Washington State: Bembidion diligens Casey, Calosoma obsoletum Say, Pseudaptinus rufulus (LeConte), and Stenolophus lineola (Fabricius). Based on these data, the Site maintains a diverse ground beetle fauna and, due to its size and diversity of habitats, is an important repository of shrub-steppe biodiversity.
Ground state and magnetic phase transitions of the spin Lieb nanolattice: Monte Carlo simulations
Masrour, R.; Jabar, A.
2018-02-01
We study the ground state and magnetic properties of the spin Lieb nanolattice with three lattice sites with spins (S = 2 , σ = 1 / 2 , q = 3 / 2) using Monte Carlo simulations. The ground state phase diagrams of the Lieb nanolattice have been studied. The phase diagrams show some key features: coexistence between regions, points where six, eight and ten states can coexist. The total and partial magnetization of each sublattice is given and the corresponding magnetic susceptibility is also found. The variation of total magnetization with the exchange interaction RSq and Rσq of the Lieb nanolattice with three lattice sites with spins (S , σ , q) has been studied. Moreover, the total magnetization versus the fields Δ /JSσ of the Lieb nanolattice with three lattice sites with spins (S , σ , q) are established for several values of Rσq and Rsq. Magnetic hysteresis cycles of the Lieb nanolattice with three lattice sites with spins (S , σ , q) are found for several values of Rsq and temperature. We show that the superparamagnetism behaviour appears for a weak coupling value between S and q thus around the transition temperature.
Ground- and excited-state structural orientation of 2-(2`-hydroxyphenyl)benzazoles in cyclodextrins
Energy Technology Data Exchange (ETDEWEB)
Roberts, E.L.; Dey, J.; Warner, I.M. [Louisiana State Univ., Baton Rouge, LA (United States)
1996-12-12
The effects of {alpha}-, {beta}-, {gamma}-, and 2,6-di-O-methyl-{beta}-cyclodextrins (CDs) on the ground- and excited-state properties of 2-(2`-hydroxyphenyl)benzoxazole, 2-(2`-hydroxyphenyl)benzothiazole, and 2-(2`-hydroxyphenyl)benzimidazole in aqueous media are investigated. Steady-state fluorescence measurements are used to characterize the interaction of CDs with these azoles. Absorbance measurements indicate increased solubility of the azoles in aqueous solutions of CDs. Measurements of acidity constants (pK{sub a}) and data from induced circular dichroism indicate increased ground- and excited-state acidities of the phenolic protons of the molecules in the presence of CDs and axial orientation of the molecules within the CD cavity, respectively. The data further suggest a planar structure for HBO and a twisted confirmation for both HBT and HBI. The association constants of the inclusion complexes have also been estimated. These studies are further supplemented by comparative spectroscopic studies of 2-(2`-methoxyphenyl)benzothiazole in aqueous solutions of CDs. On the basis of the spectral data acquired, it is believed that the HBA molecules exist as zwitterionic tautomers in the presence of CDs. 35 refs., 6 figs., 2 tabs.
Thermodynamic framework for the ground state of a simple quantum system.
Souza, Andre M C; Nobre, Fernando D
2017-01-01
The ground state of a two-level system (associated with probabilities p and 1-p, respectively) defined by a general Hamiltonian H[over ̂]=H[over ̂]_{0}+λV[over ̂] is studied. The simple case characterized by λ=0, whose Hamiltonian H[over ̂]_{0} is represented by a diagonal matrix, is well established and solvable within Boltzmann-Gibbs statistical mechanics; in particular, it follows the third law of thermodynamics, presenting zero entropy (S_{BG}=0) at zero temperature (T=0). Herein it is shown that the introduction of a perturbation λV[over ̂] (λ>0) in the Hamiltonian may lead to a nontrivial ground state, characterized by an entropy S[p] (with S[p]≠S_{BG}[p]), if the Hermitian operator V[over ̂] is represented by a 2×2 matrix, defined by nonzero off-diagonal elements V_{12}=V_{21}=-z, where z is a real positive number. Hence, this new term in the Hamiltonian, presenting V_{12}≠0, may produce physically significant changes in the ground state, and especially, it allows for the introduction of an effective temperature θ (θ∝λz), which is shown to be a parameter conjugated to the entropy S. Based on this, one introduces an infinitesimal heatlike quantity, δQ=θdS, leading to a consistent thermodynamic framework, and by proposing an infinitesimal form for the first law, a Carnot cycle and thermodynamic potentials are obtained. All results found are very similar to those of usual thermodynamics, through the identification T↔θ, and particularly the form for the efficiency of the proposed Carnot Cycle. Moreover, S also follows a behavior typical of a third law, i.e., S→0, when θ→0.
Stensitzki, Till; Muders, Vera; Schlesinger, Ramona; Heberle, Joachim; Heyne, Karsten
2015-01-01
The primary photodynamics of channelrhodopsin-1 from Chlamydomonas augustae (CaChR1) was investigated by VIS-pump supercontinuum probe experiments from femtoseconds to 100 picoseconds. In contrast to reported experiments on channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2), we found a clear dependence of the photoreaction dynamics on varying the excitation wavelength. Upon excitation at 500 and at 550 nm we detected different bleaching bands, and spectrally distinct photoproduct absorptions in the first picoseconds. We assign the former to the ground-state heterogeneity of a mixture of 13-cis and all-trans retinal maximally absorbing around 480 and 540 nm, respectively. At 550 nm, all-trans retinal of the ground state is almost exclusively excited. Here, we found a fast all-trans to 13-cis isomerization process to a hot and spectrally broad P1 photoproduct with a time constant of (100 ± 50) fs, followed by photoproduct relaxation with time constants of (500 ± 100) fs and (5 ± 1) ps. The remaining fraction relaxes back to the parent ground state with time constants of (500 ± 100) fs and (5 ± 1) ps. Upon excitation at 500 nm a mixture of both chromophore conformations is excited, resulting in overlapping reaction dynamics with additional time constants of <300 fs, (1.8 ± 0.3) ps and (90 ± 25) ps. A new photoproduct Q is formed absorbing at around 600 nm. Strong coherent oscillatory signals were found pertaining up to several picoseconds. We determined low frequency modes around 200 cm(-1), similar to those reported for bacteriorhodopsin.
Ground-state properties and density response of quasi-one-dimensional electron systems
Agosti, Daniele; Pederiva, Francesco; Lipparini, Enrico; Takayanagi, Kazuo
1998-06-01
Ground-state properties of the quasi-one-dimensional electron gas in a quantum wire are calculated in the random-phase approximation (RPA), the ladder approximation, and the Singwi-Tosi-Land-Sjölander approximation. Numerical results are given for the exchange-correlation energy and the compressibility as a function of the electron density and the width of the wire. The dielectric response of the system has been calculated in the local field approximation and compared with the RPA result.
Fermionic stabilization and density-wave ground state of a polar condensate.
Dutta, O; Kanamoto, R; Meystre, P
2007-09-14
We examine the stability of a trapped dipolar condensate mixed with a single-component fermion gas at T=0. Whereas pure dipolar condensates with a small s-wave interaction are unstable even at small dipole-dipole interaction strength, we find that the admixture of fermions can significantly stabilize them, depending on the strength of the boson-fermion interaction. Within the stable regime we find a region where a ground state is characterized by a density wave along the soft trap direction.
GSGPEs: A MATLAB code for computing the ground state of systems of Gross-Pitaevskii equations
Caliari, Marco; Rainer, Stefan
2013-03-01
GSGPEs is a Matlab/GNU Octave suite of programs for the computation of the ground state of systems of Gross-Pitaevskii equations. It can compute the ground state in the defocusing case, for any number of equations with harmonic or quasi-harmonic trapping potentials, in spatial dimension one, two or three. The computation is based on a spectral decomposition of the solution into Hermite functions and direct minimization of the energy functional through a Newton-like method with an approximate line-search strategy. Catalogue identifier: AENT_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AENT_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1417 No. of bytes in distributed program, including test data, etc.: 13673 Distribution format: tar.gz Programming language: Matlab/GNU Octave. Computer: Any supporting Matlab/GNU Octave. Operating system: Any supporting Matlab/GNU Octave. RAM: About 100 MB for a single three-dimensional equation (test run output). Classification: 2.7, 4.9. Nature of problem: A system of Gross-Pitaevskii Equations (GPEs) is used to mathematically model a Bose-Einstein Condensate (BEC) for a mixture of different interacting atomic species. The equations can be used both to compute the ground state solution (i.e., the stationary order parameter that minimizes the energy functional) and to simulate the dynamics. For particular shapes of the traps, three-dimensional BECs can be also simulated by lower dimensional GPEs. Solution method: The ground state of a system of Gross-Pitaevskii equations is computed through a spectral decomposition into Hermite functions and the direct minimization of the energy functional. Running time: About 30 seconds for a single three-dimensional equation with d.o.f. 40 for each spatial direction (test run output).
Magnetic Polarization of the Americium J =0 Ground State in AmFe2
Magnani, N.; Caciuffo, R.; Wilhelm, F.; Colineau, E.; Eloirdi, R.; Griveau, J.-C.; Rusz, J.; Oppeneer, P. M.; Rogalev, A.; Lander, G. H.
2015-03-01
Trivalent americium has a nonmagnetic (J =0 ) ground state arising from the cancellation of the orbital and spin moments. However, magnetism can be induced by a large molecular field if Am3 + is embedded in a ferromagnetic matrix. Using the technique of x-ray magnetic circular dichroism, we show that this is the case in AmFe2 . Since ⟨Jz⟩=0 , the spin component is exactly twice as large as the orbital one, the total Am moment is opposite to that of Fe, and the magnetic dipole operator ⟨Tz⟩ can be determined directly; we discuss the progression of the latter across the actinide series.
Positive ground state solutions to Schrodinger-Poisson systems with a negative non-local term
Directory of Open Access Journals (Sweden)
Yan-Ping Gao
2015-04-01
Full Text Available In this article, we study the Schrodinger-Poisson system $$\\displaylines{ -\\Delta u+u-\\lambda K(x\\phi(xu=a(x|u|^{p-1}u, \\quad x\\in\\mathbb{R}^3, \\cr -\\Delta\\phi=K(xu^{2},\\quad x\\in\\mathbb{R}^3, }$$ with $p\\in(1,5$. Assume that $a:\\mathbb{R}^3\\to \\mathbb{R^{+}}$ and $K:\\mathbb{R}^3\\to \\mathbb{R^{+}}$ are nonnegative functions and satisfy suitable assumptions, but not requiring any symmetry property on them, we prove the existence of a positive ground state solution resolved by the variational methods.
Restoring the Pauli principle in the random phase approximation ground state
Kosov, D. S.
2017-12-01
Random phase approximation ground state contains electronic configurations where two (and more) identical electrons can occupy the same molecular spin-orbital violating the Pauli exclusion principle. This overcounting of electronic configurations happens due to quasiboson approximation in the treatment of electron-hole pair operators. We describe the method to restore the Pauli principle in the RPA wavefunction. The proposed theory is illustrated by the calculations of molecular dipole moments and electronic kinetic energies. The Hartree-Fock based RPA, which is corrected for the Pauli principle, gives the results of comparable accuracy with Møller-Plesset second order perturbation theory and coupled-cluster singles and doubles method.
Kumar, Manoj; Banerjee, Varsha; Puri, Sanjay
2017-11-08
In this paper, we study the random field Ising model (RFIM) in an external magnetic field h . A computationally efficient graph-cut method is used to study ground state (GS) morphologies in this system for three different disorder types: Gaussian, uniform and bimodal. We obtain the critical properties of this system and find that they are independent of the disorder type. We also study GS morphologies via pinned-cluster distributions, which are scale-free at criticality. The spin-spin correlation functions (and structure factors) are characterized by a roughness exponent [Formula: see text]. The corresponding scaling function is universal for all disorder types and independent of h.
Mancera, L; Takeuchi, N
2003-01-01
We have studied the structural and electronic properties of YN in rock salt (sodium chloride), caesium chloride, zinc blende and wurtzite structures using first-principles total energy calculations. Rock salt is the calculated ground state structure with a = 4.93 A, B sub 0 = 157 GPa. The experimental lattice constant is a = 4.877 A. There is an additional local minimum in the wurtzite structure with total energy 0.28 eV/unit cell higher. At high pressure (approx 138 GPa), our calculations predict a phase transformation from a NaCl to a CsCl structure.
Light-cone distribution amplitudes of the ground state bottom baryons in HQET
Energy Technology Data Exchange (ETDEWEB)
Ali, A.; Wang, W. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Hambrock, C. [Technische Univ. Dortmund (Germany); Parkhomenko, A.Ya. [P.G. Demidov Yaroslavl State Univ., Yaroslavl (Russian Federation)
2012-12-15
We provide the definition of the complete set of light-cone distribution amplitudes (LCDAs) for the ground state heavy bottom baryons with the spin-parities J{sup P}=1/2{sup +} and J{sup P}=3/2{sup +} in the heavy quark limit. We present the renormalization effects on the twist-2 light-cone distribution amplitudes and use the QCD sum rules to compute the moments of twist-2, twist-3, and twist-4 LCDAs. Simple models for the heavy baryon distribution amplitudes are analyzed with account of their scale dependence.
Highly twisted 1,2:8,9-dibenzozethrenes: Synthesis, ground state, and physical properties
Sun, Zhe
2014-08-08
Two soluble and stable 1,2:8,9-dibenzozethrene derivatives (3a,b) are synthesized through a palladium-catalyzed cyclodimerization reaction. X-ray crystallographic analysis shows that these molecules are highly twisted owing to congestion at the cove region. Broken-symmetry DFT calculations predict that they have a singlet biradical ground state with a smaller biradical character and a large singlet-triplet energy gap; these predictions are supported by NMR and electronic absorption measurements. They have small energy gaps and exhibit farred/near-infrared absorption/emission and amphoteric redox behaviors.
Topological Invariants and Ground-State Wave functions of Topological Insulators on a Torus
Directory of Open Access Journals (Sweden)
Zhong Wang
2014-01-01
Full Text Available We define topological invariants in terms of the ground-state wave functions on a torus. This approach leads to precisely defined formulas for the Hall conductance in four dimensions and the topological magnetoelectric θ term in three dimensions, and their generalizations in higher dimensions. They are valid in the presence of arbitrary many-body interactions and disorder. These topological invariants systematically generalize the two-dimensional Niu-Thouless-Wu formula and will be useful in numerical calculations of disordered topological insulators and strongly correlated topological insulators, especially fractional topological insulators.
Jastrow-like ground states for quantum many-body potentials with near-neighbors interactions
Baradaran, Marzieh; Carrasco, José A.; Finkel, Federico; González-López, Artemio
2018-01-01
We completely solve the problem of classifying all one-dimensional quantum potentials with nearest- and next-to-nearest-neighbors interactions whose ground state is Jastrow-like, i.e., of Jastrow type but depending only on differences of consecutive particles. In particular, we show that these models must necessarily contain a three-body interaction term, as was the case with all previously known examples. We discuss several particular instances of the general solution, including a new hyperbolic potential and a model with elliptic interactions which reduces to the known rational and trigonometric ones in appropriate limits.
Existence of a ground state for the confined hydrogen atom in non-relativistic QED
DEFF Research Database (Denmark)
Amour, Laurent; Faupin, Jeremy
2008-01-01
We consider a system of a hydrogen atom interacting with the quantized electromagnetic field. Instead of fixing the nucleus, we assume that the system is confined by its center of mass. This model is used in theoretical physics to explain the Lamb-Dicke effect. After a brief review...... of the literature, we explain how to verify some properly chosen binding conditions which, by [25], lead to the existence of a ground state for our model, and for all values of the fine-structure constant...
Ground state solutions for Choquard type equations with a singular potential
Directory of Open Access Journals (Sweden)
Tao Wang
2017-02-01
Full Text Available This article concerns the Choquard type equation $$ -\\Delta u+V(xu=\\Big(\\int_{\\mathbb{R}^N}\\frac{|u(y|^p}{|x-y|^{N-\\alpha}}dy\\Big |u|^{p-2}u,\\quad x\\in \\mathbb{R}^N, $$ where $N\\geq3$, $\\alpha\\in ((N-4_+,N$, $2\\leq p <(N+\\alpha/(N-2$ and V(x is a possibly singular potential and may be unbounded below. Applying a variant of the Lions' concentration-compactness principle, we prove the existence of ground state solution of the above equations.
The Ground State Energy of a Dilute Bose Gas in Dimension $n\\geq 3$
DEFF Research Database (Denmark)
Aaen, Anders Gottfred
in Rn, and a is the scattering length of V. Furthermore, for smooth and compactly supported two-body potentials, we derive an upper bound to the ground state energy with a correction term (1+γ)8π4a6ρ2|ln(a4ρ)| in 4 dimensions, where 0... dimensions. Finally, we use a grand canonical construction to give a simplified proof of the second order upper bound to the Lee-Huang-Yang formula, a result first obtained by Yau and Yin. We also test this method in 4 dimensions, but with a negative outcome....
Quantum communication for satellite-to-ground networks with partially entangled states
Chen, Na; Quan, Dong-Xiao; Pei, Chang-Xing; Yang-Hong
2015-02-01
To realize practical wide-area quantum communication, a satellite-to-ground network with partially entangled states is developed in this paper. For efficiency and security reasons, the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network. Based on this point, an efficient and secure quantum communication scheme with partially entangled states is presented. In our scheme, the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states. Thus, the security of quantum communication is guaranteed. The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices. Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high. In addition, the auxiliary quantum bit provides a heralded mechanism for successful communication. Based on the critical components that are presented in this article an efficient, secure, and practical wide-area quantum communication can be achieved. Project supported by the National Natural Science Foundation of China (Grant Nos. 61072067 and 61372076), the 111 Project (Grant No. B08038), the Fund from the State Key Laboratory of Integrated Services Networks (Grant No. ISN 1001004), and the Fundamental Research Funds for the Central Universities (Grant Nos. K5051301059 and K5051201021).
Ferromagnetic ground state of the SU(3) Hubbard model on the Lieb lattice
Nie, Wenxing; Zhang, Deping; Zhang, Wei
2017-11-01
We investigate the magnetic properties of a repulsive fermionic SU (3 ) Hubbard model on the Lieb lattice from weak to strong interaction by means of the mean-field approximation. To validate the method we employed, we first discuss the SU (2 ) Hubbard model at the mean-field level, and find that our results are consistent with known rigorous theorems. We then extend the calculation to the case of SU (3 ) symmetry. We find that, at 4 /9 filling, the SU (3 ) symmetry spontaneously breaks into the SU (2 )×U (1 ) symmetry in the ground state, leading to a staggered ferromagnetic state for any repulsive U at zero temperature. We then investigate the stability of the ferromagnetic state by relaxing the filling away from 4 /9 , and conclude that the ferromagnetic state is sensitive but robust to fillings, as it can persist within a certain filling regime. We also apply the mean-field approximation to finite temperature to calculate the critical temperature and the critical entropy of the ferromagnetic state. As the resulting critical entropy per particle is significantly greater than what can be realized in experiments, we expect some quasi-long-range-ordered features of such a ferromagnetic state can be realized and observed with fermionic alkaline-earth-metal(-like) atoms loaded into optical lattices.
Properties of ground states of atomic nuclei in self-consistent theory of finite fermi-system
Energy Technology Data Exchange (ETDEWEB)
Sapershtejn, Eh.E.; Khodel' , V.A. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow. Inst. Atomnoj Ehnergii)
1983-05-01
Ground states of atomic nuclei are described within the framework of the self-consistent theory of finite Fermi systems. The developed approach is compared with the Hartree-Fock method with effective forces.
Ground state of the geometrically frustrated compound Tb{sub 2}Sn{sub 2}O{sub 7}
Energy Technology Data Exchange (ETDEWEB)
Chapuis, Y [CEA/DSM/Departement de Recherche Fondamentale sur la Matiere Condensee, F-38054 Grenoble (France); Yaouanc, A [CEA/DSM/Departement de Recherche Fondamentale sur la Matiere Condensee, F-38054 Grenoble (France); Reotier, P Dalmas de [CEA/DSM/Departement de Recherche Fondamentale sur la Matiere Condensee, F-38054 Grenoble (France); Pouget, S [CEA/DSM/Departement de Recherche Fondamentale sur la Matiere Condensee, F-38054 Grenoble (France); Fouquet, P [Institut Laue-Langevin, Boite Postale 156X, F-38042 Grenoble Cedex 9 (France); Cervellino, A [Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institut, CH-5232 Villigen-PSI (Switzerland); Forget, A [CEA/DSM/Departement de Recherche sur l' Etat Condense, les Atomes et les Molecules, F-91191 Gif sur Yvette (France)
2007-11-07
Despite the observation of magnetic neutron reflections at low temperatures, muon-spin experiments have suggested the ground state of the geometrically frustrated magnetic material Tb{sub 2}Sn{sub 2}O{sub 7} to be dynamical. This unique situation requires additional characterizations of this magnetic ground state. Here we report a neutron spin-echo investigation which supports the existence of a dynamical component in the ground state. This result is backed by a thorough analysis of the diffraction profiles. A physical model is put forward in which the energy splitting between the ground and first excited states of the Tb{sup 3+} ion is comparable to other energies present in this frustrated system.
1976-03-01
Student pilots receiving all instruction in an aircraft and student pilots who received a portion of their flight training in a ground trainer were compared in terms of flying proficiency, psychological (anxiety) states during training, and certain p...
Zethrenes, Extended p -Quinodimethanes, and Periacenes with a Singlet Biradical Ground State
Sun, Zhe
2014-08-19
ConspectusResearchers have studied polycyclic aromatic hydrocarbons (PAHs) for more than 100 years, and most PAHs in the neutral state reported so far have a closed-shell electronic configuration in the ground state. However, recent studies have revealed that specific types of polycyclic hydrocarbons (PHs) could have a singlet biradical ground state and exhibit unique electronic, optical, and magnetic activities. With the appropriate stabilization, these new compounds could prove useful as molecular materials for organic electronics, nonlinear optics, organic spintronics, organic photovoltaics, and energy storage devices. However, before researchers can use these materials to design new devices, they need better methods to synthesize these molecules and a better understanding of the fundamental relationship between the structure and biradical character of these compounds and their physical properties. Their biradical character makes these compounds difficult to synthesize. These compounds are also challenging to physically characterize and require the use of various experimental techniques and theoretic methods to comprehensively describe their unique properties.In this Account, we will discuss the chemistry and physics of three types of PHs with a significant singlet biradical character, primarily developed in our group. These structures are zethrenes, Z-shaped quinoidal hydrocarbons; hydrocarbons that include a proaromatic extended p-quinodimethane unit; and periacenes, acenes fused in a peri-Arrangement. We used a variety of synthetic methods to prepare these compounds and stabilized them using both thermodynamic and kinetic approaches. We probed their ground-state structures by electronic absorption, NMR, ESR, SQUID, Raman spectroscopy, and X-ray crystallography and also performed density functional theory calculations. We investigated the physical properties of these PHs using various experimental methods such as one-photon absorption, two-photon absorption
Energy Technology Data Exchange (ETDEWEB)
Ellis, J. Michael; Altman, Michael D.; Cash, Brandon; Haidle, Andrew M.; Kubiak, Rachel L.; Maddess, Matthew L.; Yan, Youwei; Northrup, Alan B. (Merck)
2016-12-08
Optimization of a series of highly potent and kinome selective carbon-linked carboxamide spleen tyrosine kinase (Syk) inhibitors with favorable drug-like properties is described. A pervasive Ames liability in an analogous nitrogen-linked carboxamide series was obviated by replacement with a carbon-linked moiety. Initial efforts lacked on-target potency, likely due to strain induced between the hinge binding amide and solvent front heterocycle. Consideration of ground state and bound state energetics allowed rapid realization of improved solvent front substituents affording subnanomolar Syk potency and high kinome selectivity. These molecules were also devoid of mutagenicity risk as assessed via the Ames test using the TA97a Salmonella strain.
On large amplitude motions of simplest amides in the ground and excited electronic states
Tukachev, N. V.; Bataev, V. A.; Godunov, I. A.
2017-01-01
For the formamide, acetamide, N-methylformamide and N-methylacetamide molecules in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states equilibrium geometry parameters, harmonic vibrational frequencies, barriers to conformational transitions and conformer energy differences were estimated by means of MP2, CCSD(T), CASSCF, CASPT2 and MRCI ab initio methods. One-, two- and three-dimensional potential energy surface (PES) sections corresponding to different large amplitude motions (LAM) were calculated by means of MP2/aug-cc-pVTZ (S0) and CASPT2/cc-pVTZ (S1,T1). For these molecules, in each excited electronic state six minima were found on 2D PES sections. Using PES sections, different anharmonic vibrational problems were solved and the frequencies of large amplitude vibrations were determined.
Conformational analysis of acetamide in the ground and lowest excited electronic states
Tukachev, N. V.; Bataev, V. A.; Godunov, I. A.
2017-05-01
For acetamide molecule (CH3CONH2) in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states calculations of equilibrium geometry parameters, harmonic vibrational frequencies and barriers to conformational transitions (also conformer energy differences in excited states) using following ab initio methods: MP2, CCSD(T), CASSCF, CASPT2 and MRCI were performed. One-, two- and three-dimensional potential energy surface (PES) sections by different large amplitude motions (LAM) coordinates were calculated by means of MP2/aug-cc-pVTZ (S0) and CASPT2/cc-pVTZ (S1, T1). As a result of electronic excitation, both CCON and CNH2 fragments become pyramidal. On 2D PES sections by torsion (CN) and inversion coordinates there are six minima forming three pairs of enantiomers. Using PES sections different anharmonic vibrational problems were solved and the frequencies of large amplitude vibrations were estimated.
Spin-singlet Quantum Ground State in Zigzag Spin Ladder Cu(CF3 COO)2.
Danilovich, Igor L; Karpova, Elena V; Morozov, Igor V; Ushakov, Alexey V; Streltsov, Sergey V; Shakin, Alexander A; Volkova, Olga S; Zvereva, Elena A; Vasiliev, Alexander N
2017-09-20
The copper salt of trifluoroacetic acid, Cu(CF3 COO)2 , offers a new platform to investigate the quantum ground states of low-dimensional magnets. In practice, it realizes the ideal case of a solid hosting essentially isolated magnetic monolayers. These entities are constituted by well-separated two-leg half-integer spin ladders organized in a zigzag fashion. The ladders are comprised of dimeric units of edge-sharing tetragonal pyramids coupled through carbon ions. The spin-gap state in this compound was revealed by static and dynamic magnetic measurements. No indications of long range magnetic ordering down to liquid helium temperature were obtained in specific heat measurements. First principles calculations allow estimation of the main exchange interaction parameters, J⊥ =176 K and J∥ =12 K, consistent with the weakly interacting dimers model. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Studies on the Magnetic Ground State of a Spin Möbius Strip.
Newton, Graham N; Hoshino, Norihisa; Matsumoto, Takuto; Shiga, Takuya; Nakano, Motohiro; Nojiri, Hiroyuki; Wernsdorfer, Wolfgang; Furukawa, Yuji; Oshio, Hiroki
2016-09-26
Here we report the synthesis, structure and detailed characterisation of three n-membered oxovanadium rings, Nan [(V=O)n Nan (H2 O)n (α, β, or γ-CD)2 ]⋅m H2 O (n=6, 7, or 8), prepared by the reactions of (V=O)SO4 ⋅x H2 O with α, β, or γ-cyclodextrins (CDs) and NaOH in water. Their alternating heterometallic vanadium/sodium cyclic core structures were sandwiched between two CD moieties such that O-Na-O groups separated the neighbouring vanadyl ions. Antiferromagnetic interactions between the S=1/2 vanadyl ions led to S=0 ground states for the even-membered rings, but to two quasi-degenerate S=1/2 states for the spin-frustrated heptanuclear cluster. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Totipotent Embryonic Stem Cells Arise in Ground-State Culture Conditions
DEFF Research Database (Denmark)
Morgani, Sophie M; Canham, Maurice A; Nichols, Jennifer
2013-01-01
Embryonic stem cells (ESCs) are derived from mammalian embryos during the transition from totipotency, when individual blastomeres can make all lineages, to pluripotency, when they are competent to make only embryonic lineages. ESCs maintained with inhibitors of MEK and GSK3 (2i) are thought...... not directly support Nanog-positive epiblast-like ESCs. Thus, 2i and LIF support a totipotent state comparable to early embryonic cells that coexpress embryonic and extraembryonic determinants....... to represent an embryonically restricted ground state. However, we observed heterogeneous expression of the extraembryonic endoderm marker Hex in 2i-cultured embryos, suggesting that 2i blocked development prior to epiblast commitment. Similarly, 2i ESC cultures were heterogeneous and contained a Hex...
Systematics of ground state multiplets of atomic nuclei in the delta-interaction approach
Energy Technology Data Exchange (ETDEWEB)
Imasheva, L. T.; Ishkhanov, B. S.; Stepanov, M. E., E-mail: stepanov@depni.sinp.msu.ru [Moscow State University, Faculty of Physics (Russian Federation); Tretyakova, T. Yu. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)
2015-12-15
Pairing forces between nucleons in an atomic nucleus strongly influence its structure. One of the manifestations of pair interaction is the ground state multiplet (GSM) formation in the spectrum of low-lying excited states of even–even nuclei. The value of GSM splitting is determined by the value of pair interaction of nucleons; for each isotope, it can be estimated on the basis of experimental nuclear masses. The quality of this estimate is characterized by the degree of reproduction of GSM levels in the nucleus. The GSM systematics in even–even nuclei with a pair of identical nucleons in addition to the filled nuclear core is considered on the basis of delta interaction.
On large amplitude motions of simplest amides in the ground and excited electronic states
Directory of Open Access Journals (Sweden)
Tukachev N.V.
2017-01-01
Full Text Available For the formamide, acetamide, N-methylformamide and N-methylacetamide molecules in the ground (S0 and lowest excited singlet (S1 and triplet (T1 electronic states equilibrium geometry parameters, harmonic vibrational frequencies, barriers to conformational transitions and conformer energy differences were estimated by means of MP2, CCSD(T, CASSCF, CASPT2 and MRCI ab initio methods. One-, two- and three-dimensional potential energy surface (PES sections corresponding to different large amplitude motions (LAM were calculated by means of MP2/aug-cc-pVTZ (S0 and CASPT2/cc-pVTZ (S1,T1. For these molecules, in each excited electronic state six minima were found on 2D PES sections. Using PES sections, different anharmonic vibrational problems were solved and the frequencies of large amplitude vibrations were determined.
Correlated basis functions theory of light nuclei. Pt. 1. General description and ground states
Energy Technology Data Exchange (ETDEWEB)
Bosca, M.C.; Guardiola, R.
1988-01-18
The correlated basis functions theory is applied to the description of light (p-shell) nuclei. The interaction used is the Reid potential, in the V8 (central, spin, tensor and spin-orbit) and V6 (no spin-orbit term) forms. Our work includes state-dependent correlation functions, and their radial components are determined by solving the corresponding Euler-Lagrange equations with a healing condition at distance d and with a null derivative; in addition, we impose the sequential condition or the Pauli condition so as to insure convergence. We present results corresponding to the ground state of all nuclei in the p-shell. Our results present a good qualitative behaviour, but are in clear disagreement with experimental values.
Ground and excited states for exotic three-body atomic systems
Directory of Open Access Journals (Sweden)
Gasaneo G.
2010-04-01
Full Text Available An Angular Correlated Conﬁguration Interaction method is extended and applied to exotic threebody atomic systems with general masses. A recently proposed angularly correlated basis set is used to construct, simultaneously and with a single diagonalization, ground and excited states wave functions which: (i satisfy exactly Kato cusp conditions at the two-body coalescence points; (ii have only linear parameters; (iii show a fast convergency rate for the energy; (iv form an orthogonal set. The eﬃciency of the construction is illustrated by the study a variety of three-body atomic systems [m1− m2− m3z3+ ] with two negatively charged light particles, with 123 diverse masses m1− and m2−, and a heavy positively charged nucleus m3z3+. The calculated ground 11S and several excited n1,3S state energies are compared with those given in the literature, when available. We also present a short discussion on the critical charge necessary to get a stable three-body system supporting two electrons, an electron and a muon, or two muons.
Precision measurement of the +25Mg ground-state hyperfine constant
Xu, Z. T.; Deng, K.; Che, H.; Yuan, W. H.; Zhang, J.; Lu, Z. H.
2017-11-01
We report an experimental determination of the ground-state hyperfine constant A of the +25Mg ions by measuring the | S1 /2,F =2 ,m =0 〉 to | S1 /2,F =3 ,m =0 〉 transition (0-0 transition) frequency of the two ground-state hyperfine energy levels. The frequency is measured by rf resonant method in a Paul trap under a magnetic field of about 0.1 mT. The result is A =-596.254 248 7(42) MHz. Different frequency shifts and uncertainties are evaluated. The main effect is quadratic Zeeman shift. Since the Paul trap is driven by rf on the electrodes, ac magnetic field can be induced by the rf at the site of the ion. The ac magnetic field causes quadratic Zeeman shift for ion frequency standards and also reduces the coherence time when the ion acts as a quantum bit. Precision measurement of this ac magnetic field can help evaluating the related uncertainty when a single-ion optical clock is established on the trap.
Hartree–Fock many-body perturbation theory for nuclear ground-states
Directory of Open Access Journals (Sweden)
Alexander Tichai
2016-05-01
Full Text Available We investigate the order-by-order convergence behavior of many-body perturbation theory (MBPT as a simple and efficient tool to approximate the ground-state energy of closed-shell nuclei. To address the convergence properties directly, we explore perturbative corrections up to 30th order and highlight the role of the partitioning for convergence. The use of a simple Hartree–Fock solution for the unperturbed basis leads to a convergent MBPT series for soft interactions, in contrast to the divergent MBPT series obtained with a harmonic oscillator basis. For larger model spaces and heavier nuclei, where a direct high-order MBPT calculation is not feasible, we perform third-order calculations and compare to advanced ab initio coupled-cluster results for the same interactions and model spaces. We demonstrate that third-order MBPT provides ground-state energies for nuclei up into the tin isotopic chain in excellent agreement with the best available coupled-cluster calculations at a fraction of the computational cost.
The B850/B875 Photosynthetic Complex Ground and Excited State are Both Coherent
Squire, R H; Rubio, A; Ingles, J R; Cunningham, W A
2016-01-01
A bacterial photosynthetic light harvesting complex PLHC absorbs a photon and transfers this energy almost perfectly at room temperature RT to a Reaction Center RC, where charge separation occurs. While there are a number of possible light absorbers involved in this process, our focus is the B850 and B875 complexes. We propose that the dominant feature of the ground states in the B850 ring and the B875 open chain are pseudo one dimensional metals due to each bacteriochlorophyll a BChl containing a coordinated magnesium ion Mg2+. The Mg ion structure undergoes a static Peierls distortion that results in symmetry breaking that changes the even spacing of the Mg/BChl molecules comprising the chains to the experimentally observed Mg/BChl dimers. The results are charge density waves CDW, one for each type of the two complexes that result in an energy gap in the single particle electronic spectrum and coherent phonon s spanning the entire rings. The ground state CDWs seem to have two functions the first is to form ...
Climate-driven ground-level ozone extreme in the fall over the Southeast United States.
Zhang, Yuzhong; Wang, Yuhang
2016-09-06
Ground-level ozone is adverse to human and vegetation health. High ground-level ozone concentrations usually occur over the United States in the summer, often referred to as the ozone season. However, observed monthly mean ozone concentrations in the southeastern United States were higher in October than July in 2010. The October ozone average in 2010 reached that of July in the past three decades (1980-2010). Our analysis shows that this extreme October ozone in 2010 over the Southeast is due in part to a dry and warm weather condition, which enhances photochemical production, air stagnation, and fire emissions. Observational evidence and modeling analysis also indicate that another significant contributor is enhanced emissions of biogenic isoprene, a major ozone precursor, from water-stressed plants under a dry and warm condition. The latter finding is corroborated by recent laboratory and field studies. This climate-induced biogenic control also explains the puzzling fact that the two extremes of high October ozone both occurred in the 2000s when anthropogenic emissions were lower than the 1980s and 1990s, in contrast to the observed decreasing trend of July ozone in the region. The occurrences of a drying and warming fall, projected by climate models, will likely lead to more active photochemistry, enhanced biogenic isoprene and fire emissions, an extension of the ozone season from summer to fall, and an increase of secondary organic aerosols in the Southeast, posing challenges to regional air quality management.
Morini, Filippo; Watanabe, Noboru; Kojima, Masataka; Deleuze, Michael Simon; Takahashi, Masahiko
2015-10-01
The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b1, 6a1, 4b2, and 1a2 orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A1, B1, and B2 symmetries, which correspond to C-H stretching and H-C-H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.
Ground-state properties of two-dimensional quantum fluid helium and hydrogen mixtures
Um, C I; Oh, H G
1998-01-01
Using a variational Jastrow wavefunction extended to include a three-body correlation function and a hypernetted chain scheme with the contributions of elementary diagrams, we analyze the ground-state energies and the structural properties of two-dimensional H- sup 4 He and H sub 2 - sup 4 He mixtures. The mixtures are in equilibrium at a lower density compared to a pure sup 4 He system because of the large zero-point energies of the hydrogen atom and molecule. We evaluate the lowering of the ground-state energies as a function of the impurity concentration and total density of mixtures. Comparing the result with boson sup 3 He- sup 4 He mixtures, we show that the shifts of energy mainly come from the difference of the zero-point energies of the impurities rather than from the interatomic potentials.We also analyze the enthalpies to study the miscibility and conclude that boson-boson mixtures are completely phase separated in their equilibria.
Equilibrium Skyrmion Lattice Ground State in a Polar Easy-plane Magnet.
Bordács, S; Butykai, A; Szigeti, B G; White, J S; Cubitt, R; Leonov, A O; Widmann, S; Ehlers, D; von Nidda, H-A Krug; Tsurkan, V; Loidl, A; Kézsmárki, I
2017-08-08
The skyrmion lattice state (SkL), a crystal built of mesoscopic spin vortices, gains its stability via thermal fluctuations in all bulk skyrmion host materials known to date. Therefore, its existence is limited to a narrow temperature region below the paramagnetic state. This stability range can drastically increase in systems with restricted geometries, such as thin films, interfaces and nanowires. Thermal quenching can also promote the SkL as a metastable state over extended temperature ranges. Here, we demonstrate more generally that a proper choice of material parameters alone guarantees the thermodynamic stability of the SkL over the full temperature range below the paramagnetic state down to zero kelvin. We found that GaV 4 Se 8 , a polar magnet with easy-plane anisotropy, hosts a robust Néel-type SkL even in its ground state. Our supporting theory confirms that polar magnets with weak uniaxial anisotropy are ideal candidates to realize SkLs with wide stability ranges.
Lifetime measurements of the first 2+ states in 104,106Zr: Evolution of ground-state deformations
Directory of Open Access Journals (Sweden)
F. Browne
2015-11-01
Full Text Available The first fast-timing measurements from nuclides produced via the in-flight fission mechanism are reported. The lifetimes of the first 2+ states in 104,106Zr nuclei have been measured via β-delayed γ-ray timing of stopped radioactive isotope beams. An improved precision for the lifetime of the 21+ state in 104Zr was obtained, τ(21+=2.90−20+25 ns, as well as a first measurement of the 21+ state in 106Zr, τ(21+=2.60−15+20 ns, with corresponding reduced transition probabilities of B(E2;21+→0g.s.+=0.39(2 e2b2 and 0.31(1 e2b2, respectively. Comparisons of the extracted ground-state deformations, β2=0.39(1 (104Zr and β2=0.36(1 (106Zr with model calculations indicate a persistence of prolate deformation. The data show that 104Zr is the most deformed of the neutron-rich Zr isotopes measured so far.
Deaggregation of Probabilistic Ground Motions in the Central and Eastern United States
Harmsen, S.; Perkins, D.; Frankel, A.
1999-01-01
Probabilistic seismic hazard analysis (PSHA) is a technique for estimating the annual rate of exceedance of a specified ground motion at a site due to known and suspected earthquake sources. The relative contributions of the various sources to the total seismic hazard are determined as a function of their occurrence rates and their ground-motion potential. The separation of the exceedance contributions into bins whose base dimensions are magnitude and distance is called deaggregation. We have deaggregated the hazard analyses for the new USGS national probabilistic ground-motion hazard maps (Frankel et al., 1996). For points on a 0.2?? grid in the central and eastern United States (CEUS), we show color maps of the geographical variation of mean and modal magnitudes (M??, M??) and distances (D??, D??) for ground motions having a 2% chance of exceedance in 50 years. These maps are displayed for peak horizontal acceleration and for spectral response accelerations of 0.2, 0.3, and 1.0 sec. We tabulate M??, D??, M??, and D?? for 49 CEUS cities for 0.2- and 1.0-sec response. Thus, these maps and tables are PSHA-derived estimates of the potential earthquakes that dominate seismic hazard at short and intermediate periods in the CEUS. The contribution to hazard of the New Madrid and Charleston sources dominates over much of the CEUS; for 0.2-sec response, over 40% of the area; for 1.0-sec response, over 80% of the area. For 0.2-sec response, D?? ranges from 20 to 200 km, for 1.0 sec, 30 to 600 km. For sites influenced by New Madrid or Charleston, D is less than the distance to these sources, and M?? is less than the characteristic magnitude of these sources, because averaging takes into account the effect of smaller magnitude and closer sources. On the other hand, D?? is directly the distance to New Madrid or Charleston and M?? for 0.2- and 1.0-sec response corresponds to the dominating source over much of the CEUS. For some cities in the North Atlantic states, short
The reactions of ground and excited state sodium atoms with hydrogen halide molecules
Weiss, P. S.; Mestdagh, J. M.; Covinsky, M. H.; Balko, B. A.; Lee, Y. T.
1988-10-01
The reactions of ground and excited state Na atoms with hydrogen halide (HX) molecules have been studied using the crossed molecular beams method. With both increasing translational and increasing electronic energy, the reactive cross sections increase in the reactions of HCl and HBr. From product angular and velocity distributions detailed center-of-mass information is derived. For the reactions of Na (3 2S 1/2, 3 2P 1/2, 4 2D 5/2, 5 2S 1/2) with HCl, the product NaCl is back-scattered with respect to the incoming Na atom in the center-of-mass frame of reference. The reaction of each Na state studied with HCl is direct and proceeds via collinear and near-collinear Na-Cl-H approach geometries. For the Na (3 2P 3/2) and Na (4 2D 5/2) reactions with HCl the predominant transition state symmetry is 2Σ in a collinear (C ∞ν) Na-Cl-H geometry. This is consistent with the reaction proceeding via electron transfer from the Na atom to the halide atom. Absolute reactive cross sections for each state of Na studied with HCl were determined by comparison with both small and large angle elastic scattering. We were unable to observe Na atoms with over 4 eV of electronic energy react with HF up to collision energies of 13 kcal/mole.
Electron impact excitation cross sections and rates from the ground state of atomic calcium
Samson, A M
2001-01-01
New R-matrix calculations are presented for electron excitation of atomic calcium. The target state expansion includes 22 states: 4s sup 2 sup 1 S; 4snl sup 1 sup , sup 3 L, where nl is 3d, 4p, 5s, 5p, 4d and 4f; 3d4p sup 1 sup , sup 3 P,D,F; and 4p sup 2 sup 3 P, sup 1 D, sup 1 S terms. The calculation is in LS coupling, and configuration interaction involving 3p subshell correlation is included. Electron impact excitation cross sections from the 4s sup 2 ground state to the next 10 states are tabulated for low energies, and thermally averaged effective collision strengths are tabulated over a range of electron temperatures from 1000 to 10,000 K. Comparisons are made with previous cross sections calculations for the 4s sup 2 -4s4p sup 3 P deg. transition; excellent agreement is found with experimentally derived rates for 4s sup 2 -4s4p sup 1 P deg
Ground Water Atlas of the United States: Segment 4, Oklahoma, Texas
Ryder, Paul D.
1996-01-01
The two States, Oklahoma and Texas, that compose Segment 4 of this Atlas are located in the south-central part of the Nation. These States are drained by numerous rivers and streams, the largest being the Arkansas, the Canadian, the Red, the Sabine, the Trinity, the Brazos, the Colorado, and the Pecos Rivers and the Rio Grande. Many of these rivers and their tributaries supply large amounts of water for human use, mostly in the eastern parts of the two States. The large perennial streams in the east with their many associated impoundments coincide with areas that have dense populations. Large metropolitan areas such as Oklahoma City and Tulsa, Okla., and Dallas, Fort Worth, Houston, and Austin, Tex., are supplied largely or entirely by surface water. However, in 1985 more than 7.5 million people, or about 42 percent of the population of the two States, depended on ground water as a source of water supply. The metropolitan areas of San Antonio and El Paso, Tex., and numerous smaller communities depend largely or entirely on ground water for their source of supply. The ground water is contained in aquifers that consist of unconsolidated deposits and consolidated sedimentary rocks. This chapter describes the geology and hydrology of each of the principal aquifers throughout the two-State area. Precipitation is the source of all the water in Oklahoma and Texas. Average annual precipitation ranges from about 8 inches per year in southwestern Texas to about 56 inches per year in southeastern Texas (fig. 1). In general, precipitation increases rather uniformly from west to east in the two States. Much of the precipitation either flows directly into rivers and streams as overland runoff or indirectly as base flow that discharges from aquifers where the water has been stored for some time. Accordingly, the areal distribution of average annual runoff from 1951 to 1980 (fig. 2) reflects that of average annual precipitation. Average annual runoff in the two-State area ranges
Decadal-scale changes of pesticides in ground water of the United States, 1993-2003
Bexfield, L.M.
2008-01-01
Pesticide data for ground water sampled across the United States between 1993-1995 and 2001-2003 by the U.S. Geological Survey National Water-Quality Assessment Program were evaluated for trends in detection frequency and concentration. The data analysis evaluated samples collected from a total of 362 wells located in 12 local well networks characterizing shallow ground water in agricultural areas and six local well networks characterizing the drinking water resource in areas of variable land use. Each well network was sampled once during 1993-1995 and once during 2001-2003. The networks provide an overview of conditions across a wide range of hydrogeologic settings and in major agricultural areas that vary in dominant crop type and pesticide use. Of about 80 pesticide compounds analyzed, only six compounds were detected in ground water from at least 10 wells during both sampling events. These compounds were the triazine herbicides atrazine, simazine, and prometon; the acetanilide herbicide metolachlor; the urea herbicide tebuthiuron; and an atrazine degradate, deethylatrazine (DEA). Observed concentrations of these compounds generally were <0.12 ??g L-1. At individual wells, changes in concentrations typically were <0.02 ??g L-1. Data analysis incorporated adjustments for changes in laboratory recovery as assessed through laboratory spikes. In wells yielding detectable concentrations of atrazine, DEA, and prometon, concentrations were significantly lower (?? = 0.1) in 2001-2003 than in 1993-1995, whereas detection frequency of these compounds did not change significantly. Trends in atrazine concentrations at shallow wells in agricultural areas were found to be consistent overall with recent atrazine use data. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.
Ground Motion Prediction Equations for the Central and Eastern United States
Seber, D.; Graizer, V.
2015-12-01
New ground motion prediction equations (GMPE) G15 model for the Central and Eastern United States (CEUS) is presented. It is based on the modular filter based approach developed by Graizer and Kalkan (2007, 2009) for active tectonic environment in the Western US (WUS). The G15 model is based on the NGA-East database for the horizontal peak ground acceleration and 5%-damped pseudo spectral acceleration RotD50 component (Goulet et al., 2014). In contrast to active tectonic environment the database for the CEUS is not sufficient for creating purely empirical GMPE covering the range of magnitudes and distances required for seismic hazard assessments. Recordings in NGA-East database are sparse and cover mostly range of Mindustry (Vs=2800 m/s). The number of model predictors is limited to a few measurable parameters: moment magnitude M, closest distance to fault rupture plane R, average shear-wave velocity in the upper 30 m of the geological profile VS30, and anelastic attenuation factor Q0. Incorporating anelastic attenuation Q0 as an input parameter allows adjustments based on the regional crustal properties. The model covers the range of magnitudes 4.010 Hz) and is within the range of other models for frequencies lower than 2.5 Hz
Lisewski, Andreas Martin; Lichtarge, Olivier
2010-08-01
Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network’s Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.
Ground-state properties of LiH by reptation quantum Monte Carlo methods.
Ospadov, Egor; Oblinsky, Daniel G; Rothstein, Stuart M
2011-05-07
We apply reptation quantum Monte Carlo to calculate one- and two-electron properties for ground-state LiH, including all tensor components for static polarizabilities and hyperpolarizabilities to fourth-order in the field. The importance sampling is performed with a large (QZ4P) STO basis set single determinant, directly obtained from commercial software, without incurring the overhead of optimizing many-parameter Jastrow-type functions of the inter-electronic and internuclear distances. We present formulas for the electrical response properties free from the finite-field approximation, which can be problematic for the purposes of stochastic estimation. The α, γ, A and C polarizability values are reasonably consistent with recent determinations reported in the literature, where they exist. A sum rule is obeyed for components of the B tensor, but B(zz,zz) as well as β(zzz) differ from what was reported in the literature. This journal is © the Owner Societies 2011
Ground state structure and conductivity of quantum wires of infinite length and finite width
Malet, F.; Pi, M.; Barranco, M.; Lipparini, E.
2005-11-01
We have studied the ground state structure of quantum strips within the local spin-density approximation, for a range of electronic densities between ˜5×104 and 2×106cm-1 and several strengths of the lateral confining potential. The results have been used to address the conductance G of quantum strips. At low density, when only one subband is occupied, the system is fully polarized and G takes a value close to 0.7(2e2/h) , decreasing with increasing electron density in agreement with experiments. At higher densities the system becomes paramagnetic and G takes a value near (2e2/h) , showing a similar decreasing behavior with increasing electron density. In both cases, the physical parameter that determines the value of the conductance is the ratio K/K0 of the compressibility of the system to the free one.
Ground state and magnetic phase transitions of orthoferrite DyFeO3
Zhao, Z. Y.; Zhao, X.; Zhou, H. D.; Zhang, F. B.; Li, Q. J.; Fan, C.; Sun, X. F.; Li, X. G.
2014-06-01
Low-temperature thermal conductivity (κ), as well as magnetization (M) and electric polarization (P), of multiferroic orthoferrite DyFeO3 single crystals are studied with H ∥c. When the crystal is cooled in zero field, M, P, and κ all consistently exhibit irreversible magnetic-field dependencies. In particular, with 500 mK ultra-low-T (T mK) κ (H) shows a different irreversibility and there is only one transition when the field is swept both up and down. All the results indicate a complex low-T H-T phase diagram involving successive magnetic phase transitions of the Fe3+ spins. In particular, the ground state, obtained with cooling to sub-Kelvin temperatures in zero field, is found to be an unexplored phase.
Energy Technology Data Exchange (ETDEWEB)
Kunishige, Sachi; Katori, Toshiharu; Baba, Masaaki, E-mail: baba@kuchem.kyoto-u.ac.jp [Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Nakajima, Masakazu; Endo, Yasuki [Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902 (Japan)
2015-12-28
We observed microwave absorption spectra of some deuterated benzenes and accurately determined the rotational constants of all H/D isotopomers in the ground vibrational state. Using synthetic analysis assuming that all bond angles are 120°, the mean bond lengths were obtained to be r{sub 0}(C–C) = 1.3971 Å and r{sub 0}(C–H) = r{sub 0}(C–D) = 1.0805 Å. It has been concluded that the effect of deuterium substitution on the molecular structure is negligibly small and that the mean bond lengths of C–H and C–D are identical unlike small aliphatic hydrocarbons, in which r{sub 0}(C–D) is about 5 mÅ shorter than r{sub 0}(C–H). It is considered that anharmonicity is very small in the C–H stretching vibration of aromatic hydrocarbons.
Ground state magnetization of conduction electrons in graphene with Zeeman effect
Energy Technology Data Exchange (ETDEWEB)
Escudero, F., E-mail: federico.escudero@uns.edu.ar [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Ardenghi, J.S., E-mail: jsardenhi@gmail.com [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Sourrouille, L., E-mail: lsourrouille@yahoo.es [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Jasen, P., E-mail: pvjasen@uns.edu.ar [Departamento de Física, Universidad Nacional del Sur, Av. Alem 1253, B8000CPB Bahía Blanca (Argentina); Instituto de Física del Sur (IFISUR, UNS-CONICET), Av. Alem 1253, B8000CPB Bahía Blanca (Argentina)
2017-05-01
In this work we address the ground state magnetization in graphene, considering the Zeeman effect and taking into account the conduction electrons in the long wavelength approximation. We obtain analytical expressions for the magnetization at T=0 K, where the oscillations given by the de Haas van Alphen (dHvA) effect are present. We find that the Zeeman effect modifies the magnetization by introducing new peaks associated with the spin splitting of the Landau levels. These peaks are very small for typical carrier densities in graphene, but become more important for higher densities. The obtained results provide insight of the way in which the Zeeman effect modifies the magnetization, which can be useful to control and manipulate the spin degrees of freedom. - Highlights: • The magnetization has peaks whenever the last energy level changes discontinuously. • The peaks amplitude depends on the electron density. • The Zeeman effect introduces new peaks in the magnetization.
A Continuous Family of Equilibria in Ferromagnetic Media are Ground States
Su, Xifeng; de la Llave, Rafael
2017-09-01
We show that a foliation of equilibria (a continuous family of equilibria whose graph covers all the configuration space) in ferromagnetic transitive models are ground states. The result we prove is very general, and it applies to models with long range and many-body interactions. As an application, we consider several models of networks of interacting particles including models of Frenkel-Kontorova type on Z^d and one-dimensional quasi-periodic media. The result above is an analogue of several results in the calculus of variations (fields of extremals) and in PDE's. Since the models we consider are discrete and long range, new proofs need to be given. We also note that the main hypothesis of our result (the existence of foliations of equilibria) is the conclusion (using KAM theory) of several recent papers. Hence, we obtain that the KAM solutions recently established are minimizers when the interaction is ferromagnetic and transitive (these concepts are defined later).
Ground state oxygen holes and the metal-insulator transition in rare earth nickelates
Energy Technology Data Exchange (ETDEWEB)
Schmitt, Thorsten; Bisogni, Valentina; Huang, Yaobo; Strocov, Vladimir [Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Catalano, Sara; Gibert, Marta; Scherwitzl, Raoul; Zubko, Pavlo; Triscone, Jean-Marc [Departement de Physique de la Matiere Condensee, University of Geneva (Switzerland); Green, Robert J.; Balandeh, Shadi; Sawatzky, George [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada)
2015-07-01
Perovskite rare-earth (Re) nickelates ReNiO{sub 3} continue to attract a lot of interest owing to their intriguing properties like a sharp metal to insulator transition (MIT), unusual magnetic order and expected superconductivity in specifically tuned super-lattices. Full understanding of these materials, however, is hampered by the difficulties in describing their electronic ground state (GS). From X-ray absorption (XAS) at the Ni 2p{sub 3/2} edge of thin films of NdNiO{sub 3} and corresponding RIXS maps vs. incident and transferred photon energies we reveal that the electronic GS configuration of NdNiO{sub 3} is composed of delocalized and localized components. Our study conveys that a Ni 3d{sup 8}-like configuration with holes at oxygen takes on the leading role in the GS and the MIT of ReNiO{sub 3} as proposed by recent model theories.
The ground state properties of spin-aligned atomic hydrogen, deuterium, and tritium
Etters, R. D.; Dugan, J. V., Jr.; Palmer, R. W.
1975-01-01
The internal energy, pressure, and compressibility of ground-state, spin-aligned atomic hydrogen, deuterium, and tritium are calculated assuming that all pair interactions occur via the atomic triplet (spin-aligned) potential. The conditions required to obtain atomic hydrogen and its isotopes in bulk are discussed; such a development would be of value in propulsion systems because of the light mass and energetic recombination of atomic hydrogen. Results show that atomic triplet hydrogen and deuterium remain gaseous at 0 K, and that tritium forms a liquid with a binding energy of approximately -0.75 K per atom at a molar volume of 130 cu cm per mole. The pair distribution function for these systems is calculated, and the predicted superfluid behavior of atomic triplet hydrogen and tritium is briefly discussed.
Long-range interactions of excited He atoms with ground-state noble-gas atoms
Zhang, J.-Y.
2013-10-09
The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-n expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the C6 coefficients for the systems involving He(131,3S) and He(131,3P) are calculated and found to be in good agreement with directly calculated values.
A minimisation approach for computing the ground state of Gross Pitaevskii systems
Caliari, Marco; Ostermann, Alexander; Rainer, Stefan; Thalhammer, Mechthild
2009-02-01
In this paper, we present a minimisation method for computing the ground state of systems of coupled Gross-Pitaevskii equations. Our approach relies on a spectral decomposition of the solution into Hermite basis functions. Inserting the spectral representation into the energy functional yields a constrained nonlinear minimisation problem for the coefficients. For its numerical solution, we employ a Newton-like method with an approximate line-search strategy. We analyse this method and prove global convergence. Appropriate starting values for the minimisation process are determined by a standard continuation strategy. Numerical examples with two- and three-component two-dimensional condensates are included. These experiments demonstrate the reliability of our method and nicely illustrate the effect of phase segregation.
Verification of g-factors for lead monofluoride ground state, PbF
Skripnikov, L V; Titov, A V; Mawhorter, R J; Baum, A L; Sears, T J; Grabow, J -U
2015-01-01
We report the results of our theoretical study and analysis of earlier experimental data for the g-factor tensor components of the ground $^2\\Pi_{1/2}$ state of free PbF radical. The values obtained both within the relativistic coupled-cluster method combined with the generalized relativistic effective core potential approach and with our fit of the experimental data from [R.J. Mawhorter, B.S. Murphy, A.L. Baum, T.J. Sears, T. Yang, P.M. Rupasinghe, C.P. McRaven, N.E. Shafer-Ray, L.D. Alphei, J.-U. Grabow, Phys. Rev. A 84, 022508 (2011); A. Baum, B.S. thesis, Pomona College, 2011]. The obtained results agree very well with each other but contradict the previous fit performed in the cited works. Our final prediction for g-factors is $G_{\\parallel}= 0.081(5)$, $G_{\\perp}=-0.27(1)$.
Uniqueness of non-linear ground states for fractional Laplacians in R
DEFF Research Database (Denmark)
Frank, Rupert L.; Lenzmann, Enno
2013-01-01
We prove uniqueness of ground state solutions Q = Q(|x|) ≥ 0 of the non-linear equation (−Δ)sQ+Q−Qα+1=0inR,where 0 fractional Laplacian in one dimension. In particular, we answer affirmatively an open question...... recently raised by Kenig–Martel–Robbiano and we generalize (by completely different techniques) the specific uniqueness result obtained by Amick and Toland for s=12 and α = 1 in [5] for the Benjamin–Ono equation. As a technical key result in this paper, we show that the associated linearized operator L...... + = (−Δ) s +1−(α+1)Q α is non-degenerate; i.e., its kernel satisfies ker L + = span{Q′}. This result about L + proves a spectral assumption, which plays a central role for the stability of solitary waves and blowup analysis for non-linear dispersive PDEs with fractional Laplacians, such as the generalized...
Dai, Y. Y.; Wang, H.; Tao, P.; Yang, T.; Ren, W. J.; Zhang, Z. D.
2013-08-01
We show by micromagnetic simulations that a spontaneous skyrmion ground state can exist in Co/Ru/Co nanodisks without the Dzyaloshinsky-Moriya interaction, which can remain stable in the applied magnetic field along the +z direction even up to 0.44 T. The guiding center (Rx,Ry) of skyrmion defined by the moments of the topological density presents a gyration with a star-like trajectory in a pulsed magnetic field and a hexagonal trajectory after the field is switched off, which is different from that of a vortex or bubble. One of the coupled skyrmions could move without an external magnetic field, just induced by the motion of the other one due to strong interlayer magnetostatic interactions. This work sheds light on how skyrmions can be discovered in various (not limited to magnetic) systems with competing energies and contributes to the understanding of the dynamical properties of skyrmions.
On the ground and excited state of glycine-glutaric acid: A new organic material
Shkir, Mohd.; Abbas, Haider
In current work, the experimental and theoretical investigation on glycine-glutaric acid (GGA) has been reported. Single crystals of GGA were grown by slow evaporation solution technique in an aqueous solution. Crystal structure and lattice parameters of GGA were confirmed by powder X-ray diffraction analysis. The ground and excited state properties of GGA were obtained within the framework of density functional theory. The calculated infrared spectrum and the S0 → S1 transition energy were compared with the earlier reported experimental results and found in good agreement. HOMO-LUMO energy gap was calculated by using RHF/6-31G(d,p) and B3LYP/6-31G(d,p) level of theoretical calculations. Dipole moment of GGA obtained by RHF and B3LYP was found 11.84 and 10.87 D respectively.
Local convertibility of the ground state of the perturbed toric code
Santra, Siddhartha; Hamma, Alioscia; Cincio, Lukasz; Subasi, Yigit; Zanardi, Paolo; Amico, Luigi
2014-12-01
We present analytical and numerical studies of the behavior of the α -Renyi entropies in the toric code in presence of several types of perturbations aimed at studying the simulability of these perturbations to the parent Hamiltonian using local operations and classical communications (LOCC)—a property called local convertibility. In particular, the derivatives, with respect to the perturbation parameter, present different signs for different values of α within the topological phase. From the information-theoretic point of view, this means that such ground states cannot be continuously deformed within the topological phase by means of catalyst assisted local operations and classical communications (LOCC). Such LOCC differential convertibility is on the other hand always possible in the trivial disordered phase. The non-LOCC convertibility is remarkable because it can be computed on a system whose size is independent of correlation length. This method can therefore constitute an experimentally feasible witness of topological order.
Universal subleading terms in ground-state fidelity from boundary conformal field theory
Campos Venuti, Lorenzo; Saleur, Hubert; Zanardi, Paolo
2009-03-01
The study of the (logarithm of the) fidelity, i.e., of the overlap amplitude, between ground states of Hamiltonians corresponding to different coupling constants provides a valuable insight on critical phenomena. When the parameters are infinitesimally close, it is known that the leading term behaves as O(Lα) ( L system size), where α is equal to the spatial dimension d for gapped systems, and otherwise depends on the critical exponents. Here we show that when parameters are changed along a critical manifold, a subleading O(1) term can appear. This term, somewhat similar to the topological entanglement entropy, depends only on the system’s universality class and encodes nontrivial information about the topology of the system. We relate it to universal g factors and partition functions of (boundary) conformal field theory in d=1 and d=2 dimensions. Numerical checks are presented on the simple example of the XXZ chain.
This EnviroAtlas dataset includes the average below ground live tree root dry biomass estimate for the Watershed Boundary Dataset (WBD) 12-digit Hydrologic Unit (HUC) in kg/m from the 2000 National Biomass and Carbon Dataset developed by the Woods Hole Research Center. This dataset was produced by the US EPA to support research and online mapping activities related to EnviroAtlas. EnviroAtlas (https://www.epa.gov/enviroatlas) allows the user to interact with a web-based, easy-to-use, mapping application to view and analyze multiple ecosystem services for the contiguous United States. The dataset is available as downloadable data (https://edg.epa.gov/data/Public/ORD/EnviroAtlas) or as an EnviroAtlas map service. Additional descriptive information about each attribute in this dataset can be found in its associated EnviroAtlas Fact Sheet (https://www.epa.gov/enviroatlas/enviroatlas-fact-sheets).
Direct observation of the hyperfine transition of ground-state positronium.
Yamazaki, T; Miyazaki, A; Suehara, T; Namba, T; Asai, S; Kobayashi, T; Saito, H; Ogawa, I; Idehara, T; Sabchevski, S
2012-06-22
We report the first direct measurement of the hyperfine transition of the ground state positronium. The hyperfine structure between ortho-positronium and para-positronium is about 203 GHz. We develop a new optical system to accumulate about 10 kW power using a gyrotron, a mode converter, and a Fabry-Pérot cavity. The hyperfine transition has been observed with a significance of 5.4 standard deviations. The transition probability is measured to be A = 3.1(-1.2)(+1.6) × 10(-8) s(-1) for the first time, which is in good agreement with the theoretical value of 3.37 × 10(-8) s(-1).
Lisewski, Andreas Martin; Lichtarge, Olivier
2010-08-15
Recurrent international financial crises inflict significant damage to societies and stress the need for mechanisms or strategies to control risk and tamper market uncertainties. Unfortunately, the complex network of market interactions often confounds rational approaches to optimize financial risks. Here we show that investors can overcome this complexity and globally minimize risk in portfolio models for any given expected return, provided the relative margin requirement remains below a critical, empirically measurable value. In practice, for markets with centrally regulated margin requirements, a rational stabilization strategy would be keeping margins small enough. This result follows from ground states of the random field spin glass Ising model that can be calculated exactly through convex optimization when relative spin coupling is limited by the norm of the network's Laplacian matrix. In that regime, this novel approach is robust to noise in empirical data and may be also broadly relevant to complex networks with frustrated interactions that are studied throughout scientific fields.
Classical ground states of Heisenberg and X Y antiferromagnets on the windmill lattice
Jeevanesan, Bhilahari; Orth, Peter P.
2014-10-01
We investigate the classical Heisenberg and planar (X Y ) spin models on the windmill lattice. The windmill lattice is formed out of two widely occurring lattice geometries: a triangular lattice is coupled to its dual honeycomb lattice. Using a combination of iterative minimization, heat-bath Monte Carlo simulations, and analytical calculations, we determine the complete ground-state phase diagram of both models and find the exact energies of the phases. The phase diagram shows a rich phenomenology due to competing interactions and hosts, in addition to collinear and various coplanar phases, also intricate noncoplanar phases. We briefly outline different paths to an experimental realization of these spin models. Our extensive study provides a starting point for the investigation of quantum and thermal fluctuation effects.
The ground state of the ${\\rm H}_3^+$ molecular ion: a physics behind
Turbiner, A V
2012-01-01
Five physics mechanisms of interaction leading to binding of the ${\\rm H}_3^+$ molecular ion are identified, realized in a form of variational trial functions and their respective total energies are calculated. Each of them provides subsequently the most accurate approximation for the Born-Oppenheimer (BO) ground state energy among (two-three-seven)-parametric trial functions being correspondingly, H$_2$-molecule plus proton (two variational parameters), H$_2^+$-ion plus H-atom (three variational parameters) and generalized Guillemin-Zener (seven variational parameters). These trial functions are chosen following a criterion of physical adequacy, they include the electronic correlation in the exponential form $\\sim\\exp{(\\gamma r_{12})}$, where $\\gamma$ is a variational parameter. Superpositions of two different mechanisms of binding are investigated and a particular one, which is a generalized Guillemin-Zener plus H$_2$-molecule plus proton (ten variational parameters), provides the total energy at the equili...
Santos, J. T.; Li, J.; Ilves, J.; Ockeloen-Korppi, C. F.; Sillanpää, M.
2017-10-01
Cavity optomechanics is a tool to study the interaction between light and micromechanical motion. Here we observe optomechanical physics in a truly macroscopic oscillator close to the quantum ground state. As the mechanical system, we use a mm-sized piezoelectric quartz disk oscillator. Its motion is coupled to a charge qubit which translates the piezo-induced charge into an effective radiation-pressure interaction between the disk and a microwave cavity. We measure the thermal motion of the lowest mechanical shear mode at 7 MHz down to 30 mK, corresponding to roughly 102 quanta in a 20 mg oscillator. We estimate that with realistic parameters, it is possible to utilize the back-action cooling by the qubit in order to control macroscopic motion by a single Cooper pair. The work opens up opportunities for macroscopic quantum experiments.
Study of some electronics properties of new superconductor Sr2VO3FeAs in ground state
Directory of Open Access Journals (Sweden)
M Majidiyan
2010-09-01
Full Text Available In this paper, some electronics properties of new superconductor Sr2VO3FeAs, such as density of states, band structure, density of electron cloud and bound lengths in the ground state have been calculated. According to N(Ef in ground state CV/T value has been estimated. The calculations were performed in the framework of density functional theory (DFT, using the full potential linearized augmented plane wave (FP-LAPW method with the general gradient approximation (GGA.
Directory of Open Access Journals (Sweden)
M.V. Tkach
2015-09-01
Full Text Available The partial summing of infinite range of diagrams for the two-phonon mass operator of polaron described by Frohlich Hamiltonian is performed using the Feynman-Pines diagram technique. The renormalized spectral parameters of ground and first excited (phonon repeat polaron state are accurately calculated for the weak electron-phonon coupling at T=0 K. It is shown that the stronger electron-phonon interaction shifts the energy of both states into low-energy region of the spectra. The ground state stays stationary and the excited one - decays at bigger coupling constant.
Timonen, Virpi; Conlon, Catherine; Scharf, Thomas; Carney, Gemma
2013-09-01
The relationship between class and intergenerational solidarities in the public and private spheres calls for further conceptual and theoretical development. This article discusses the findings from the first wave of a qualitative longitudinal study entitled Changing Generations , conducted in Ireland in 2011-2012, comprising 100 in-depth interviews with men and women across the age and socioeconomic spectrums. Constructivist grounded theory analysis of the data gives rise to the following postulates: (1) intergenerational solidarity at the family level is strongly contoured by socioeconomic status (SES); (2) intergenerational solidarity evolves as family generations observe each others' practices and adjust their expectations accordingly; (3) intergenerational solidarity within families is also shaped by the public sphere (the welfare state) that generates varying expectations and levels of solidarity regarding State supports for different age groups, again largely dependent on SES; (4) the liberal welfare state context, especially at a time of economic crisis, enhances the significance of intergenerational solidarity within families. We conclude by calling for research that is attuned to age/generation, gender and class, and how these operate across the family and societal levels.
Distribution of major herbicides in ground water of the United States
Barbash, Jack E.; Thelin, Gail P.; Kolpin, Dana W.; Gilliom, Robert J.
1999-01-01
Information on the concentrations and spatial distributions of pesticides and their transformation products, or degradates, in the hydrologic system is essential for managing pesticide use in both agricultural and nonagricultural settings to protect water resources. This report examines the occurrence of selected herbicides and their degradates in ground water, primarily on the basis of results from two large-scale, multistate investigations by the U.S. Geological Survey—the National Water-Quality Assessment (NAWQA) Program and the Midwest Pesticide Study (MWPS). The NAWQA pesticide data were derived from 2,227 sites (wells and springs) sampled in 20 major hydrologic basins across the United States from 1993 to 1995; the MWPS data were obtained from the sampling of 303 wells in a 12-state area of the northern midcontinent from 1991 to 1994. Data are presented for seven high-use herbicides: five of current interest to the U.S. Environmental Protection Agency for designing Pesticide Management Plans (atrazine, cyanazine, simazine, alachlor and metolachlor), a largely nonagricultural herbicide (prometon), and an agricultural herbicide first registered in 1994 for use in the United States (acetochlor).
Zhang, Tianyuan; Evangelista, Francesco A
2016-09-13
In this work we propose a novel approach to solve the Schrödinger equation which combines projection onto the ground state with a path-filtering truncation scheme. The resulting projector configuration interaction (PCI) approach realizes a deterministic version of the full configuration interaction quantum Monte Carlo (FCIQMC) method [Booth, G. H.; Thom, A. J. W.; Alavi, A. J. Chem. Phys. 2009, 131, 054106]. To improve upon the linearized imaginary-time propagator, we develop an optimal projector scheme based on an exponential Chebyshev expansion in the limit of an infinite imaginary time step. After writing the exact projector as a path integral in determinant space, we introduce a path filtering procedure that truncates the size of the determinantal basis and approximates the Hamiltonian. The path filtering procedure is controlled by one real threshold that determines the accuracy of the PCI energy and is not biased toward any determinant. Therefore, the PCI approach can equally well describe static and dynamic electron correlation effects. This point is illustrated in benchmark computations on N2 at both equilibrium and stretched geometries. In both cases, the PCI achieves chemical accuracy with wave functions that contain less than 0.5% determinants of full CI space. We also report computations on the ground state of C2 with up to quaduple-ζ basis sets and wave functions as large as 200 million determinants, which allow a direct comparison of the PCI, FCIQMC, and density matrix renormalization group (DMRG) methods. The size of the PCI wave function grows modestly with the number of unoccupied orbitals, and its accuracy may be tuned to match that of FCIQMC and DMRG.
Ground Water Atlas of the United States: Segment 7, Idaho, Oregon, Washington
Whitehead, R.L.
1994-01-01
The States of Idaho, Oregon, and Washington, which total 248,730 square miles, compose Segment 7 of this Atlas. The area is geologically and topographically diverse and contains a wealth of scenic beauty, natural resources, and ground and surface water that generally are suitable for all uses. Most of the area of Segment 7 is drained by the Columbia River, its tributaries, and other streams that discharge to the Pacific Ocean. Exceptions are those streams that flow to closed basins in southeastern Oregon and northern Nevada and to the Great Salt Lake in northern Utah. The Columbia River is one of the largest rivers in the Nation. The downstream reach of the Columbia River forms most of the border between Oregon and Washington. In 1990, Idaho, Oregon, and Washington had populations of 1.0 million, 2.8 million, and 4.9 million, respectively. The more densely populated parts are in lowland areas and stream valleys. Many of the mountains, the deserts, and the upland areas of Idaho, Oregon, and Washington lack major population centers. Large areas of Idaho and Oregon are uninhabited and are mostly public land (fig. 1) where extensive ground-water development is restricted. Surface water is abundant in Idaho, Oregon, and Washington, though not always available when and where needed. In some places, surface water provides much of the water used for public-supply, domestic and commercial, agricultural (primarily irrigation and livestock watering), and industrial purposes. In arid parts of Segment 7, however, surface water has long been fully appropriated, chiefly for irrigation. Ground water is used when and where surface-water supplies are lacking. Ground water is commonly available to shallow wells that are completed in unconsolidated-deposit aquifers that consist primarily of sand and gravel but contain variable quantities of clay and silt. Many large-yield public-supply and irrigation wells and thousands of domestic wells are completed in these types of aquifers
Vaezi, Mohammad-Sadegh; Vaezi, Abolhassan
2017-10-01
We study the concept of entanglement distance between two quantum states, which quantifies the amount of information shared between their reduced density matrices (RDMs). Using analytical arguments combined with density-matrix renormalization group (DMRG) and exact diagonalization (ED) calculations, we show that for gapless systems the entanglement distance has power law dependence on the energy separation and subsystem size, with αE and αℓ exponents, respectively. Using conformal field theory (CFT) we find αE=2 and αℓ=4 for Abelian theories with c =1 , as in the case of free fermions. For non-Abelian CFTs αE=0 , and αℓ is twice the conformal dimension of the thermal primary fields. For instance, for Z3 parafermion CFT αE=1 and αℓ=4 /5 . For gapped 1+1 dimensional (1+1D) fermion systems, we show that the entanglement distance divides the low energy excitations into two branches with different values of αE and αℓ. These two branches are related to momentum transfers near zero and π . We also demonstrate that the entanglement distance reaches its maximum for degenerate states related through nonlocal operators such as Wilson loops. For example, degenerate ground states (GSs) of 2+1D topological states have maximum entanglement distance. In contrast, degenerate GSs related through confined anyon excitations such as genons have minimum entanglement distance. Various implications of this concept for quantum simulations are discussed. Finally, based on the ideas developed we discuss the computational complexity of DMRG algorithms that are capable of finding all degenerate GSs.
Probing ground and low-lying excited states for HIO{sub 2} isomers
Energy Technology Data Exchange (ETDEWEB)
Souza, Gabriel L. C. de [Departamento de Química, Universidade Federal de Mato Grosso, Cuiabá, Mato Grosso 78060-900 (Brazil); Instituto de Ciências Exatas e Tecnologia, Universidade Federal do Amazonas, Itacoatiara, Amazonas 69100-000 (Brazil); Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2 (Canada); Brown, Alex, E-mail: alex.brown@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2 (Canada)
2014-12-21
We present a computational study on HIO{sub 2} molecules. Ground state properties such as equilibrium structures, relative energetics, vibrational frequencies, and infrared intensities were obtained for all the isomers at the coupled-cluster with single and double excitations as well as perturbative inclusion of triples (CCSD(T)) level of theory with the aug-cc-pVTZ-PP basis set and ECP-28-PP effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. The HOIO structure is confirmed as the lowest energy isomer. The relative energies are shown to be HOIO < HOOI < HI(O)O. The HO(O)I isomer is only stable at the density functional theory (DFT) level of theory. The transition states determined show interconversion of the isomers is possible. In order to facilitate future experimental identification, vibrational frequencies are also determined for all corresponding deuterated species. Vertical excitation energies for the three lowest-lying singlet and triplet excited states were determined using the configuration interaction singles, time-dependent density functional theory (TD-DFT)/B3LYP, TD-DFT/G96PW91, and equation of motion-CCSD approaches with the LANL2DZ basis set plus effective core potential for iodine and the aug-cc-pVTZ basis set for hydrogen and oxygen atoms. It is shown that HOIO and HOOI isomers have excited states accessible at solar wavelengths (<4.0 eV) but these states have very small oscillator strengths (<2 × 10{sup −3})
Cabrera-Diaz, Elisa; Barbosa-Cardenas, Claudia M; Perez-Montaño, Julia A; Gonzalez-Aguilar, Delia; Pacheco-Gallardo, Carlos; Barba, Jeannette
2013-12-01
The occurrence, serotype diversity, and antimicrobial resistance of Salmonella bacteria in commercial ground beef at retail establishments were investigated. Salmonella was isolated from 135 (56.7%) of 238 ground beef samples collected at the same number of butcher's shops located in three municipalities of Jalisco State, Mexico, during an 11-month period. The isolation frequency differed by municipality (P retail establishments increase the consumer's exposure to Salmonella.
Millimeter/submillimeter-wave spectrum of the VCl(+) radical in its X (4)Sigma(-) ground state.
Halfen, D T; Ziurys, L M
2009-11-26
The pure rotational spectrum of the molecular ion VCl(+) (X (4)Sigma(-)) has been recorded from 274 to 419 GHz using a combination of millimeter direct absorption and velocity modulation spectroscopy. This study is the first spectroscopic measurement of this species in the laboratory, which has also enabled the determination of the ground state term, (4)Sigma(-). VCl(+) was produced in an AC discharge of VCl(4) and argon. Fifteen and eleven rotational transitions were recorded for the V(35)Cl(+) and V(37)Cl(+) isotopologues, respectively. The fine structure splittings of the (4)Sigma(-) state were found to deviate significantly from a case (b) pattern. Specifically, spin components from adjacent rotational transitions were found to overlap in frequency. Unusual vanadium hyperfine splittings were also observed in the VCl(+) spectra; the expected vanadium octet was clearly present for the F(2) and F(3) spin components but was partially collapsed and reversed in frequency ordering in the F(1) and F(4) cases. The data were analyzed in a global fit, and rotational, fine structure, and hyperfine constants were determined. For VCl(+), the values of both the spin-spin and spin-rotation parameters are extremely large, as were the third-order hyperfine and spin-rotation terms, b(s) and gamma(s). For example, the spin-spin constant is lambda = 417 900(22 700) MHz, while gamma = 6567(51) MHz. The values of these constants indicate a high density of excited electronic states close to the ground state, which contribute to second and third-order spin-orbit coupling. The hyperfine constants suggest a sigma(1)pi(2) electron configuration, as opposed to sigma(1)delta(2), as found in VS and VO. The bond length of VCl(+), r(0) = 2.119(2) A, is shorter than that of VCl by 0.1 A, which has r(0) = 2.219 A. The decrease in bond length is attributed to an increase in the electrostatic attraction between V(2+) and Cl(-), as opposed to V(+) and Cl(-) for VCl.
Gerbi, Andrea; Buzio, Renato; Kawale, Shrikant; Bellingeri, Emilio; Martinelli, Alberto; Bernini, Cristina; Tresca, Cesare; Capone, Massimo; Profeta, Gianni; Ferdeghini, Carlo
2017-12-01
We investigate with scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT) calculations the surface structures and the electronic properties of Fe1+y Te thin films grown by pulsed laser deposition. Contrary to the regular arrangement of antiferromagnetic nanostripes previously reported on cleaved single-crystal samples, the surface of Fe1+y Te thin films displays a peculiar distribution of spatially inhomogeneous nanostripes. Both STM and DFT calculations show the bias-dependent nature of such features and support the interpretation of spin-polarized tunneling between the FeTe surface and an unintentionally magnetized tip. In addition, the spatial inhomogeneity is interpreted as a purely electronic effect related to changes in hybridization and Fe–Fe bond length driven by local variations in the concentration of excess interstitial Fe cations. Unexpectedly, the surface density of states measured by STS strongly evolves with temperature in close proximity to the antiferromagnetic–paramagnetic first-order transition, and reveals a large pseudogap of 180–250 meV at about 50–65 K. We believe that in this temperature range a phase transition takes place, and the system orders and locks into particular combinations of orbitals and spins because of the interplay between excess interstitial magnetic Fe and strongly correlated d-electrons.
Gerbi, Andrea; Buzio, Renato; Kawale, Shrikant; Bellingeri, Emilio; Martinelli, Alberto; Bernini, Cristina; Tresca, Cesare; Capone, Massimo; Profeta, Gianni; Ferdeghini, Carlo
2017-11-09
We investigate with scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT) calculations the surface structures and the electronic properties of Fe 1+y Te thin films grown by pulsed laser deposition. Contrary to the regular arrangement of antiferromagnetic nanostripes previously reported on cleaved single-crystal samples, the surface of Fe 1+y Te thin films displays a peculiar distribution of spatially inhomogeneous nanostripes. Both STM and DFT calculations show the bias-dependent nature of such features and support the interpretation of spin-polarized tunneling between the FeTe surface and an unintentionally magnetized tip. In addition, the spatial inhomogeneity is interpreted as a purely electronic effect related to changes in hybridization and Fe-Fe bond length driven by local variations in the concentration of excess interstitial Fe cations. Unexpectedly, the surface density of states measured by STS strongly evolves with temperature in close proximity to the antiferromagnetic-paramagnetic first-order transition, and reveals a large pseudogap of 180-250 meV at about 50-65 K. We believe that in this temperature range a phase transition takes place, and the system orders and locks into particular combinations of orbitals and spins because of the interplay between excess interstitial magnetic Fe and strongly correlated d-electrons.
Gerbi, Andrea; Buzio, Renato; Kawale, Shrikant S; Bellingeri, Emilio; Martinelli, Alberto; Bernini, Cristina; Tresca, Cesare; Capone, Massimo; Profeta, Gianni; Ferdeghini, Carlo
2017-10-04
We investigate by Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Density Functional Theory (DFT) calculations the surface structures and the electronic properties of Fe1+yTe thin films grown by pulsed laser deposition. Contrary to the regular arrangement of antiferromagnetic nanostripes previously reported on cleaved single-crystal samples, the surface of Fe1+yTe thin films displays a peculiar distribution of spatially inhomogeneous nanostripes. Both STM and DFT calculations show the bias-dependent nature of such features and support the interpretation of spin-polarized tunneling between the FeTe surface and an unintentionally magnetized tip. In addition, the spatial inhomogeneity is interpreted as a purely electronic effect, related to changes in hybridization and Fe-Fe bond length driven by local variations in the concentration of excess interstitial Fe cations. Unexpectedly, the surface density of states measured by STS strongly evolves with temperature in close proximity to the antiferromagnetic-paramagnetic first-order transition, and reveals a large pseudogap of 180-250 meV at about 50-65 K. We believe that in this temperature range a phase transition takes place and the system orders and locks into particular combinations of orbitals and spins, because of the interplay between excess interstitial magnetic Fe and strongly correlated d-electrons. © 2017 IOP Publishing Ltd.
Schiffer, Jamie M; Feher, Victoria A; Malmstrom, Robert D; Sida, Roxana; Amaro, Rommie E
2016-10-18
Proteins commonly sample a number of conformational states to carry out their biological function, often requiring transitions from the ground state to higher-energy states. Characterizing the mechanisms that guide these transitions at the atomic level promises to impact our understanding of functional protein dynamics and energy landscapes. The leucine-99-to-alanine (L99A) mutant of T4 lysozyme is a model system that has an experimentally well characterized excited sparsely populated state as well as a ground state. Despite the exhaustive study of L99A protein dynamics, the conformational changes that permit transitioning to the experimentally detected excited state (∼3%, ΔG ∼2 kcal/mol) remain unclear. Here, we describe the transitions from the ground state to this sparsely populated excited state of L99A as observed through a single molecular dynamics (MD) trajectory on the Anton supercomputer. Aside from detailing the ground-to-excited-state transition, the trajectory samples multiple metastates and an intermediate state en route to the excited state. Dynamic motions between these states enable cavity surface openings large enough to admit benzene on timescales congruent with known rates for benzene binding. Thus, these fluctuations between rare protein states provide an atomic description of the concerted motions that illuminate potential path(s) for ligand binding. These results reveal, to our knowledge, a new level of complexity in the dynamics of buried cavities and their role in creating mobile defects that affect protein dynamics and ligand binding. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Bader, A.N.; Pivovarenko, V.; Demchenko, A.P.; Ariese, F.; Gooijer, C.
2004-01-01
We studied the mechanisms of excited-state intramolecular proton transfer (ESIPT) and ground-state back proton transfer (BPT) in 3-hydroxyflavone (3HF) at cryogenic temperatures. The focus was on substituents that change the distribution of electronic density on the chromophore and their influence
Huang, Wenxuan; Dacek, Stephen; Rong, Ziqin; Urban, Alexander; Cao, Shan; Luo, Chuan; Ceder, Gerbrand
2016-01-01
Lattice models, also known as generalized Ising models or cluster expansions, are widely used in many areas of science and are routinely applied to alloy thermodynamics, solid-solid phase transitions, magnetic and thermal properties of solids, and fluid mechanics, among others. However, the problem of finding the true global ground state of a lattice model, which is essential for all of the aforementioned applications, has remained unresolved, with only a limited number of results for highly simplified systems known. In this article, we present the first general algorithm to find the exact ground states of complex lattice models and to prove their global optimality, resolving this fundamental problem in condensed matter and materials theory. We transform the infinite-discrete-optimization problem into a pair of combinatorial optimization (MAX-SAT) and non-smooth convex optimization (MAX-MIN) problems, which provide upper and lower bounds on the ground state energy respectively. By systematically converging th...
Konstantinidis, N. P.
2016-11-01
The icosahedron has a ground state magnetization discontinuity in an external magnetic field when classical spins mounted on its vertices are coupled according to the antiferromagnetic Heisenberg model. This is so even if there is no magnetic anisotropy in the Hamiltonian. The discontinuity is a consequence of the frustrated nature of the interactions, which originates in the topology of the cluster. Here it is found that the addition of the next order isotropic spin exchange interaction term in the Hamiltonian, the biquadratic exchange interaction, significantly enriches the classical ground state magnetic response. For relatively weak biquadratic interaction new discontinuities emerge, while for even stronger the number of discontinuities for this small molecule can go up to seven, accompanied by a susceptibility discontinuity. These results demonstrate the possibility of using a small entity like the icosahedron as a magnetic unit whose ground state spin configuration and magnetization can be tuned between many different non-overlapping regimes with the application of an external field.
Gartside, Jack C.; Arroo, Daan M.; Burn, David M.; Bemmer, Victoria L.; Moskalenko, Andy; Cohen, Lesley F.; Branford, Will R.
2018-01-01
Arrays of non-interacting nanomagnets are widespread in data storage and processing. As current technologies approach fundamental limits on size and thermal stability, enhancing functionality through embracing the strong interactions present at high array densities becomes attractive. In this respect, artificial spin ices are geometrically frustrated magnetic metamaterials that offer vast untapped potential due to their unique microstate landscapes, with intriguing prospects in applications from reconfigurable logic to magnonic devices or hardware neural networks. However, progress in such systems is impeded by the inability to access more than a fraction of the total microstate space. Here, we demonstrate that topological defect-driven magnetic writing—a scanning probe technique—provides access to all of the possible microstates in artificial spin ices and related arrays of nanomagnets. We create previously elusive configurations such as the spin-crystal ground state of artificial kagome dipolar spin ices and high-energy, low-entropy `monopole-chain' states that exhibit negative effective temperatures.
FeCr2S4 in magnetic fields: possible evidence for a multiferroic ground state
Bertinshaw, J.; Ulrich, C.; Günther, A.; Schrettle, F.; Wohlauer, M.; Krohns, S.; Reehuis, M.; Studer, A. J.; Avdeev, M.; Quach, D. V.; Groza, J. R.; Tsurkan, V.; Loidl, A.; Deisenhofer, J.
2014-01-01
We report on neutron diffraction, thermal expansion, magnetostriction, dielectric, and specific heat measurements on polycrystalline FeCr2S4 in external magnetic fields. The ferrimagnetic ordering temperatures TC ≈ 170 K and the transition at TOO ≈ 10 K, which has been associated with orbital ordering, are only weakly shifted in magnetic fields up to 9 T. The cubic lattice parameter is found to decrease when entering the state below TOO. The magnetic moments of the Cr- and Fe-ions are reduced from the spin-only values throughout the magnetically ordered regime, but approach the spin-only values for fields >5.5 T. Thermal expansion in magnetic fields and magnetostriction experiments indicate a contraction of the sample below about 60 K. Below TOO this contraction is followed by a moderate expansion of the sample for fields larger than ~4.5 T. The transition at TOO is accompanied by an anomaly in the dielectric constant. The dielectric constant depends on both the strength and orientation of the external magnetic field with respect to the applied electric field for T magnetic-field-induced change of the dielectric constant and the magnetic-field dependent magnetization is observed. This behaviour is consistent with the existence of a ferroelectric polarization and a multiferroic ground state below 10 K. PMID:25123960
Structures of Annulenes and Model Annulene Systems in the Ground and Lowest Excited States
Directory of Open Access Journals (Sweden)
Pier Remigio Salvi
2010-11-01
Full Text Available The paper introduces general considerations on structural properties of aromatic, antiaromatic and non-aromatic conjugated systems in terms of potential energy along bond length alternation and distortion coordinates, taking as examples benzene, cyclobutadiene and cyclooctatetraene. Pentalene, formally derived from cyclooctatetraene by cross linking, is also considered as a typical antiaromatic system. The main interest is concerned with [n]annulenes and model [n]annulene molecular systems, n ranging from 10 to 18. The rich variety of conformational and configurational isomers and of dynamical processes among them is described. Specific attention is devoted to bridged [10]- and [14]annulenes in the ground and lowest excited states as well as to s-indacene and biphenylene. Experimental data obtained from vibrational and electronic spectroscopies are discussed and compared with ab initio calculation results. Finally, porphyrin, tetraoxaporphyrin dication and diprotonated porphyrin are presented as annulene structures adopting planar/non-planar geometries depending on the steric hindrance in the inner macrocycle ring. Radiative and non-radiative relaxation processes from excited state levels have been observed by means of time-resolved fluorescence and femtosecond transient absorption spectroscopy. A short account is also given of porphycene, the structural isomer of porphyrin, and of porphycene properties.
Path integral Monte Carlo ground state approach: formalism, implementation, and applications
Yan, Yangqian; Blume, D.
2017-11-01
Monte Carlo techniques have played an important role in understanding strongly correlated systems across many areas of physics, covering a wide range of energy and length scales. Among the many Monte Carlo methods applicable to quantum mechanical systems, the path integral Monte Carlo approach with its variants has been employed widely. Since semi-classical or classical approaches will not be discussed in this review, path integral based approaches can for our purposes be divided into two categories: approaches applicable to quantum mechanical systems at zero temperature and approaches applicable to quantum mechanical systems at finite temperature. While these two approaches are related to each other, the underlying formulation and aspects of the algorithm differ. This paper reviews the path integral Monte Carlo ground state (PIGS) approach, which solves the time-independent Schrödinger equation. Specifically, the PIGS approach allows for the determination of expectation values with respect to eigen states of the few- or many-body Schrödinger equation provided the system Hamiltonian is known. The theoretical framework behind the PIGS algorithm, implementation details, and sample applications for fermionic systems are presented.
Preparation of HD{sup +}-Ions in the Ro-vibrational ground state
Energy Technology Data Exchange (ETDEWEB)
Schneider, Tobias; Roth, Bernhard; Duncker, Hannes; Hansen, Michael; Vasilyev, Sergey; Ernsting, Ingo; Schiller, Stephan [Institut fuer Experimentalphysik, Universitaet Duesseldorf (Germany)
2009-07-01
Being the most simple heteronuclear molecule, the HD{sup +} molecular ion is an ideal model system for testing the predictions of ab-initio theoretical molecular structure calculations using high precision laser spectroscopy. Two interesting perspectives are improved tests of QED effects in molecules and an alternative determination of the electron to proton mass ration m{sub e}/m{sub p}. One important prerequisite for high precision spectroscopic measurements is the ability to control the translational as well as internal degrees of freedom of the molecules. For molecular ions stored in an ion trap the motion of the molecules can be cooled via sympathetic cooling with laser cooled atomic ions. Cooling of the internal degrees of freedom is more difficult since the sympathetic cooling does not affect the internal degrees of freedom and in non-cryogenic environments interaction with black body radiation will distribute the molecular population over several ro-vibrational states. For HD{sup +} we developed an optical pumping scheme that allows to prepare most of the molecular ions in the ro-vibrational ground state. We present first experimental results.
Magnetic ground state of the Ising-like antiferromagnet DyScO3
Wu, L. S.; Nikitin, S. E.; Frontzek, M.; Kolesnikov, A. I.; Ehlers, G.; Lumsden, M. D.; Shaykhutdinov, K. A.; Guo, E.-J.; Savici, A. T.; Gai, Z.; Sefat, A. S.; Podlesnyak, A.
2017-10-01
We report on the low-temperature magnetic properties of the DyScO3 perovskite, which were characterized by means of single crystal and powder neutron scattering, and by magnetization measurements. Below TN=3.15 K, Dy3 + moments form an antiferromagnetic structure with an easy axis of magnetization lying in the a b plane. The magnetic moments are inclined at an angle of ˜±28∘ to the b axis. We show that the ground-state Kramers doublet of Dy3 + is made up of primarily |±15 /2 〉 eigenvectors and well separated by a crystal field from the first excited state at E1=24.9 meV. This leads to an extreme Ising single-ion anisotropy, M⊥/M∥˜0.05 . The transverse magnetic fluctuations, which are proportional to M⊥2/M∥2 , are suppressed, and only moment fluctuations along the local Ising direction are allowed. We also found that the Dy-Dy dipolar interactions along the crystallographic c axis are two to four times larger than in-plane interactions.
Case Study for the ARRA-Funded Ground Source Heat Pump Demonstration at Ball State University
Energy Technology Data Exchange (ETDEWEB)
Im, Piljae [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Xiaobing [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Henderson, Jr., Hugh [CDH Energy Corp., Beijing (China)
2016-12-01
With funding provided by the American Recovery and Reinvestment Act (ARRA), 26 ground-source heat pump (GSHP) projects were competitively selected in 2009 to demonstrate the benefits of GSHP systems and innovative technologies for cost reduction and/or performance improvement. One of the selected demonstration projects is a district central GSHP system installed at Ball State University (BSU) in Muncie, IN. Prior to implementing the district GSHP system, 47 major buildings in BSU were served by a central steam plant with four coal-fired and three natural-gas-fired steam boilers. Cooling was provided by five water-cooled centrifugal chillers at the District Energy Station South (DESS). The new district GSHP system replaced the existing coal-fired steam boilers and conventional water-cooled chillers. It uses ground-coupled heat recovery (HR) chillers to meet the simultaneous heating and cooling demands of the campus. The actual performance of the GSHP system was analyzed based on available measured data from August 2015 through July 2016, construction drawings, maintenance records, personal communications, and construction costs. Since Phase 1 was funded in part by the ARRA grant, it is the focus of this case study. The annual energy consumption of the GSHP system was calculated based on the available measured data and other related information. It was compared with the performance of a baseline scenario— a conventional water-cooled chiller and natural-gas-fired boiler system, both of which meet the minimum energy efficiencies allowed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE 90.1-2013). The comparison was made to determine source energy savings, energy cost savings, and CO2 emission reductions achieved by the GSHP system. A cost analysis was performed to evaluate the simple payback of the GSHP system. The following sections summarize the results of the analysis, the lessons learned, and recommendations for improvement
Energy Technology Data Exchange (ETDEWEB)
Bolte, Jens, E-mail: jens.bolte@rhul.ac.uk [Department of Mathematics, Royal Holloway, University of London, Egham TW20 0EX (United Kingdom); Kerner, Joachim, E-mail: joachim.kerner@fernuni-hagen.de [Department of Mathematics and Computer Science, FernUniversität in Hagen, Hagen 58084 (Germany)
2016-04-15
In this paper we investigate Bose-Einstein condensation into the one-particle ground state in interacting quantum many-particle systems on graphs. We extend previous results obtained for particles on an interval and show that even arbitrarily small repulsive two-particle interactions destroy the condensate in the one-particle ground state present in the non-interacting Bose gas. Our results also cover singular two-particle interactions, such as the well-known Lieb-Liniger model, in the thermodynamic limit.
Blancher, P.J.; Jacobs, B.; Couturier, A.; Beardmore, C.J.; Dettmers, R.; Dunn, Erica H.; Easton, W.; Iñigo-Elias, Eduardo E.; Rich, T.D.; Rosenberg, K.V.; Ruth, J.M.
2006-01-01
To effectively conserve migratory landbirds, we need to be involved in conservation beyond our political borders. This has been a central tenet of Partners in Flight (PIF) since the initiative began in 1990 with a focus on Nearctic-Neotropical migrants. Implementation of this concept has also been fundamental to the success of the North American Waterfowl Management Plan (e.g., NAWMP 2004). Actions by individual states, provinces and territories are key to the success of PIF efforts at the continental scale, and great progress has been made in recent years though various initiatives. Currently, U.S. state Wildlife Action Plans are outlining a vast array of actions to benefit priority species. However, it is also very important to take action in regions that support these same species at the other end of their migratory movements, to ensure effective protection year-round (Rappole et al. 1983, Webster and Marra 2005, Elliott et al. 2005). For instance, conservation action is needed on the wintering grounds for many birds that breed in Canada and the U.S. but spend a large portion of their annual cycle in Mexico, the West Indies, Central and/or South America. In this document we use maps to summarize migratory connections between individual U.S. states, Canadian provinces & territories and the regions that support the same birds at the other end of migration. The maps give a general picture of where birds go, providing a starting point for targeting action. With this information in hand, decision-makers can explore partnerships and mechanism that would help further conservation action outside their bordersa?|
Energy Technology Data Exchange (ETDEWEB)
Hauer, Juergen; Buckup, Tiago [Fachbereich Chemie, Physikalische Chemie, Philipps-Universitaet Marburg, Hans-Meerwein-Strasse, D-35043 Marburg (Germany); Motzkus, Marcus [Fachbereich Chemie, Physikalische Chemie, Philipps-Universitaet Marburg, Hans-Meerwein-Strasse, D-35043 Marburg (Germany)], E-mail: motzkus@staff.uni-marburg.de
2008-06-23
Quantum control spectroscopy (QCS) is used as a tool to study, address selectively and enhance vibrational wavepacket motion in large solvated molecules. By contrasting the application of Fourier-limited and phase-modulated excitation on different electronic states, the interplay between the controllability of vibrational coherence and electronic resonance is revealed. We contrast control on electronic ground and excited state by introducing an additional pump beam prior to a DFWM-sequence (Pump-DFWM). Via phase modulation of this initial pump pulse, coherent control is extended to structural evolution on the vibrationally hot ground state (hot-S{sub 0}) and lowest lying excited state (S{sub 1}) of {beta}-carotene. In an open loop setup, the control scenarios for these different electronic states are compared in their effectiveness and mechanism.
Non-local ground-state functional for quantum spin chains with translational broken symmetry
Energy Technology Data Exchange (ETDEWEB)
Libero, Valter L.; Penteado, Poliana H.; Veiga, Rodrigo S. [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica
2011-07-01
Full text. Thanks to the development and use of new materials with special doping, it becomes relevant the study of Heisenberg spin-chains with broken translational symmetry, induced for instance by finite-size effects, bond defects or by impurity spin in the chain. The exact numerical results demands huge computational efforts, due to the size of the Hilbert space involved and the lack of symmetry to exploit. Density Functional Theory (DFT) has been considered a simple alternative to obtain ground-state properties for such systems. Usually, DFT starts with a uniform system to build the correlation energy and after implement a local approximation to construct local functionals. Based on our prove of the Hohenberg-Kohn theorem for Heisenberg models, and in order to describe more realistic models, we have recently developed a non-local exchange functional for the ground-state energy of quantum-spin chains. A alternating-bond chain is used to obtain the correlation energy and a local unit-cell approximation - LUCA, is defined in the context of DFT. The alternating chain is a good starting point to construct functionals since it is intrinsically non-homogeneous, therefore instead of the usual local approximation (like LDA for electronic systems) we need to introduce an approximation based upon a unit cell concept, that renders a non-local functional in the bond exchange interaction. The agreement with exact numerical data (obtained only for small chains, although the functional can be applied for chains with arbitrary size) is significantly better than in our previous local formulation, even for chains with several ferromagnetic or antiferromagnetic bond defects. These results encourage us to extend the concept of LUCA for chains with alternating-spin magnitudes. We also have constructed a non-local functional based on an alternating-spin chain, instead of a local alternating-bond, using spin-wave-theory. Because of its non-local nature, this functional is expected to
Xu, Jie; Chang, Chia-Chen; Walter, Eric J; Zhang, Shiwei
2011-12-21
The ground states of the two-dimensional repulsive Hubbard model are studied within the unrestricted Hartree-Fock (UHF) theory. Magnetic and charge properties are determined by systematic, large-scale, exact numerical calculations, and quantified as a function of electron doping, h. In the solution of the self-consistent UHF equations, multiple initial configurations and simulated annealing are used to facilitate convergence to the global minimum. New approaches are employed to minimize finite-size effects in order to reach the thermodynamic limit. At low to moderate interacting strengths and low doping, the UHF ground state is a linear spin-density wave (l-SDW), with antiferromagnetic order and a modulating wave. The wavelength of the modulating wave is 2/h. Corresponding charge order exists but is substantially weaker than the spin order, hence holes are mobile. As the interaction is increased, the l-SDW states evolve into several different phases, with the holes eventually becoming localized. A simple pairing model is presented with analytic calculations for low interaction strength and small doping, to help understand the numerical results and provide a physical picture for the properties of the SDW ground state. By comparison with recent many-body calculations, it is shown that, for intermediate interactions, the UHF solution provides a good description of the magnetic correlations in the true ground state of the Hubbard model. © 2011 IOP Publishing Ltd Printed in the UK & the USA
Towards {sup 6}Li-{sup 40}K ground state molecules
Energy Technology Data Exchange (ETDEWEB)
Brachmann, Johannes Felix Simon
2013-02-08
The production of a quantum gas with strong long - range dipolar interactions is a major scientific goal in the research field of ultracold gases. In their ro - vibrational ground state Li-K dimers possess a large permanent dipole moment, which could possibly be exploited for the realization of such a quantum gas. A production of these molecules can be achieved by the association of Li and K at a Feshbach resonance, followed by a coherent state transfer. In this thesis, detailed theoretical an experimental preparations to achieve state transfer by means of Stimulated Raman Adiabatic Passage (STIRAP) are described. The theoretical preparations focus on the selection of an electronically excited molecular state that is suitable for STIRAP transfer. In this context, molecular transition dipole moments for both transitions involved in STIRAP transfer are predicted for the first time. This is achieved by the calculation of Franck-Condon factors and a determination of the state in which the {sup 6}Li-{sup 40}K Feshbach molecules are produced. The calculations show that state transfer by use of a single STIRAP sequence is experimentally very well feasible. Further, the optical wavelengths that are needed to address the selected states are calculated. The high accuracy of the data will allow to carry out the molecular spectroscopy in a fast and efficient manner. Further, only a comparatively narrow wavelength tuneability of the spectroscopy lasers is needed. The most suitable Feshbach resonance for the production of {sup 6}Li-{sup 40}K molecules at experimentally manageable magnetic field strengths is occurring at 155 G. Experimentally, this resonance is investigated by means of cross-dimensional relaxation. The application of the technique at various magnetic field strengths in the vicinity of the 155 G Feshbach resonance allows a determination of the resonance position and width with so far unreached precision. This reveals the production of molecules on the atomic side
Parusel, A. B.
2000-01-01
The ground and excited states of a covalently linked porphyrin-fullerene dyad in both its free-base and zinc forms (D. Kuciauskas et al., J. Phys. Chem. 100 (1996) 15926) have been investigated by semiempirical methods. The excited-state properties are discussed by investigation of the character of the molecular orbitals. All frontier MOs are mainly localized on either the donor or the acceptor subunit. Thus, the absorption spectra of both systems are best described as the sum of the spectra of the single components. The experimentally observed spectra are well reproduced by the theoretical computations. Both molecules undergo efficient electron transfer in polar but not in apolar solvents. This experimental finding is explained theoretically by explicitly considering solvent effects. The tenth excited state in the gas phase is of charge-separated character where an electron is transferred from the porphyrin donor to the fullerene acceptor subunit. This state is stabilized in energy in polar solvents due to its large formal dipole moment. The stabilization energy for an apolar environment such as benzene is not sufficient to lower this state to become the first excited singlet state. Thus, no electron transfer is observed, in agreement with experiment. In a polar environment such as acetonitrile, the charge-separated state becomes the S, state and electron transfer takes place, as observed experimentally. The flexible single bond connecting both the donor and acceptor subunits allows free rotation by ca. +/- 30 degrees about the optimized ground-state conformation. For the charge-separated state this optimized geometry has a maximum dipole moment. The geometry of the charge-separated state thus does not change relatively to the ground-state conformation. The electron-donating properties of porphyrin are enhanced in the zinc derivative due to a reduced porphyrin HOMO-LUMO energy gap. This yields a lower energy for the charge-separated state compared to the free
On the Stability of Classical Orbits of the Hydrogen Ground State in Stochastic Electrodynamics
Directory of Open Access Journals (Sweden)
Theodorus M. Nieuwenhuizen
2016-04-01
Full Text Available De la Peña 1980 and Puthoff 1987 show that circular orbits in the hydrogen problem of Stochastic Electrodynamics connect to a stable situation, where the electron neither collapses onto the nucleus nor gets expelled from the atom. Although the Cole-Zou 2003 simulations support the stability, our recent numerics always lead to self-ionisation. Here the de la Peña-Puthoff argument is extended to elliptic orbits. For very eccentric orbits with energy close to zero and angular momentum below some not-small value, there is on the average a net gain in energy for each revolution, which explains the self-ionisation. Next, an 1 / r 2 potential is added, which could stem from a dipolar deformation of the nuclear charge by the electron at its moving position. This shape retains the analytical solvability. When it is enough repulsive, the ground state of this modified hydrogen problem is predicted to be stable. The same conclusions hold for positronium.
Quasi-Two-Dimensional Metallic Ground State of Ca3Ru2O7
Yoshida, Yoshiyuki
2005-03-01
Ca3Ru2O7 is a three-dimensional antiferromagnetic metal between a first-order metal to nonmetal transition at 48 K and the antiferromagnetic ordering temperature, TN=56 K[1]. The crystal structure is the double layered Ruddlesden-Popper type with the Bb21m space group, which has both the rotation and tiling of RuO6 octahedra. We have succeeded in growing single crystals of Ca3Ru2O7 using a floating-zone method for the first time. The temperature dependence of the electrical resistivity establishes that Ca3Ru2O7 develops a quasi-two-dimensional metallic ground state below 30 K, from which the observed quantum oscillation derives. The specific heat measurement reveals the electronic specific-heat coefficient γ to be as small as 1.7 mJ/Ru mol K^2[2]. From the results of powder neutron diffractions, we proposed the most possible magnetic structure with an antiferromagnetic ordering. The field dependence of the resistivity at the metamagnetic transition around 6 T can be explained by the tunneling magnetoresistance. This work was done in collaboration with S. I. Ikeda, N. Shirakawa, C. H. Lee, M. Kosaka, and S. Katano. [1] G. Cao et al., Phys. Rev. Lett. 78 (1997) 1751. [2] Y. Yoshida et al., Phys. Rev. B 69 (2004) R220411.
Masuda, Yuichi; Nakano, Tomoko; Sugiyama, Midori
2012-05-10
Despite the importance of ultrafast (time scale exceeding 10(-11) s) intramolecular proton transfer (PT) events between electronic ground states in solution, experimental determination of the rates of such reactions has not yet been accomplished because of the limitations of the utilized methods. The objective of this study was to evaluate the PT rates of intramolecular O···H···O hydrogen-bonded systems in solution through the (1)H spin-lattice relaxation times of the hydroxyl protons, induced by the (1)H-(17)O dipolar interactions (T(1dd)(OH)), taking into account the contribution of the OH reorientational motion to T(1dd)(OH). Solutions of the benzoic acid dimer (BA dimer), 1-benzoyl-6-hydroxy-6-phenylfulvene (Fulvene), and dibenzoylmethane (DBM) were chosen as test systems. For Fulvene in CCl(4), the PT time, τ(PT), was deduced to be 7 × 10(-11) s. In the case of the BA dimer in CCl(4), the τ(PT) value was considerably greater than the OH reorientational correlation time, τ(R(OH)) = 4.3 × 10(-11) s. In contrast, the experimental results for DBM in CCl(4) indicated that the proton is located about midway between the two oxygen atoms, that is, the PT potential energy surface is a single well or a double well with a PT barrier near or below the zero-point energy.
Half-life determination of the ground state decay of ¹¹¹Ag.
Collins, S M; Harms, A V; Regan, P H
2016-02-01
The radioactive decay half-life of the β(-)-emitter (111)Ag has been measured using decay transitions identified using a high purity germanium γ-ray spectrometer. The time series of measurements of the net peak areas of the 96.8 keV, 245.4 keV and 342.1 keV γ-ray emissions following the β(-) decay of (111)Ag were made over approximately 23 days, i.e. ~3 half-life periods. The measured half-life of the ground state decay of (111)Ag was determined as 7.423 (13) days which is consistent with the Evaluated Nuclear Structure Data File (ENSDF) recommended half-life of 7.45 (1) days at k=2. Utilising all available experimental half-life values, a revised recommended half-life of 7.452 (12) days has been determined. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.
Ground State of the One Dimensional Heisenberg Model with NNN Interactions
Mancini, J. D.; Fessatidis, V.; Bowen, S. P.; Maly, J.; Murawski, R. K.
A great number of insights into a variety of complex physical many-body systems have been gleaned from the study of the of the one-dimensional Heisenberg model. There exists a number of quasi one-dimensional inorganic compounds such as TTF - CUS4C4(CF3) 4 , SRCU2O3 , VO2P2O7 and CuGeO3 for which this Hamiltonian system is relevant. For this work we shall study the one-dimensional Heisenberg Model with nearest, next nearest and next -next nearest interactions. The Hamiltonian is given by: H =J1 ∑ ksk .sk + 1 +J2 ∑ ksk .sk + 2 +J3 ∑ ksk .sk + 3 where sk represents the spin 1 / 2 operator along a chain of N sites and periodic boundary conditions is assumed for the closed chain. We note that it is further possible to describe the Coulomb interaction subject to the Pauli exclusion principle for two quantum dots an XY model. Here we shall study the ground-state energy as well as the energy gap of this system using both a Lanczos (tridiagonal) scheme as well as a generalized Moments approach.
Energy Technology Data Exchange (ETDEWEB)
Bauer, Eric D [Los Alamos National Laboratory; Booth, C H [LBNL; Walter, M D [LBNL; Kazhdan, D [LBNL; Hu, Y - J [LBNL; Lukens, Wayne [LBNL; Maron, Laurent [INSA TOULOUSE; Eisentein, Odile [UNIV MONTPELLIER 2; Anderson, Richard [LBNL
2009-01-01
Partial ytterbium f-orbital occupancy (i.e. intermediate valence) and open-shell singlet Draft 12/formation are established for a variety of bipyridine and diazabutadiene adducts to decamethylytterbocene, (C{sub 5}Me{sub 5}){sub 2}Yb or Cp*{sub 2}Yb. Data used to support this claim includes ytterbium valence measurements using Yb Lm-edge x-ray absorption near-edge structure (XANES) spectroscopy, magnetic susceptibility and Complete Active Space Self-Consistent Field (CASSCF) multi configurational calculations, as well as structural measurements compared to density-functional theory (DFT) calculations. The CASSCF calculations indicate that the intermediate valence is the result of a multiconfigurational ground state wave function that has both an open-shell singlet f{sup 13} and a closed-shell singlet f{sup 14} component. A number of other competing theories for the unusual magnetism in these materials are ruled out by the presence of intermediate valence and its lack of any significant temperature dependence. These results have implications for understanding chemical bonding not only in organolanthanide complexes, but also for organometallic chemistry in general, as well as understanding magnetic interactions in nanopartic1es and devices.
Energy Technology Data Exchange (ETDEWEB)
Booth, Corwin H.; Walter, Marc D.; Kazhdan, Daniel; Hu, Yung-Jin; Lukens, Wayne W.; Bauer, Eric D.; Maron, Laurent; Eisenstein, Odile; Andersen, Richard A.
2009-04-22
Partial ytterbium f-orbital occupancy (i.e., intermediate valence) and open-shell singlet formation are established for a variety of bipyridine and diazabutadiene adducts with decamethylytterbocene, (C5Me5)2Yb, abbreviated as Cp*2Yb. Data used to support this claim include ytterbium valence measurements using Yb LIII-edge X-ray absorption near-edge structure spectroscopy, magnetic susceptibility, and complete active space self-consistent field (CASSCF) multiconfigurational calculations, as well as structural measurements compared to density functional theory calculations. The CASSCF calculations indicate that the intermediate valence is the result of a multiconfigurational ground-state wave function that has both an open-shell singlet f13(?*)1, where pi* is the lowest unoccupied molecular orbital of the bipyridine or dpiazabutadiene ligands, and a closed-shell singlet f14 component. A number of other competing theories for the unusual magnetism in these materials are ruled out by the lack of temperature dependence of the measured intermediate valence. These results have implications for understanding chemical bonding not only in organolanthanide complexes but also for f-element chemistry in general, as well as understanding magnetic interactions in nanoparticles and devices.
Entropy Constraints in the Ground State Formation of Magnetically Frustrated Systems
Sereni, Julian G.
2018-01-01
A systematic modification of the entropy trajectory (S_m(T)) is observed at very low temperature in magnetically frustrated systems as a consequence of the constraint (S_m&g; 0) imposed by the Nernst postulate. The lack of magnetic order allows to explore and compare new thermodynamic properties by tracing the specific heat (C_m) behavior down to the sub-Kelvin range. Some of the most relevant findings are: (i) a common C_m/T|_{T→ 0} ≈ 7 J/mol K^2 `plateau' in at least five Yb-based very-heavy-fermions (VHF) compounds; (ii) quantitative and qualitative differences between VHF and standard non-Fermi-liquids; (iii) entropy bottlenecks governing the change of S_m(T) trajectories in a continuous transition into alternative ground states. A comparative analysis of S_m(T→ 0) dependencies is performed in compounds suitable for adiabatic demagnetization processes according to their partial ^2 S_m/partial T^2 derivatives.
Existence of ground state of an electron in the BDF approximation
Sok, Jérémy
2014-05-01
The Bogoliubov-Dirac-Fock (BDF) model allows us to describe relativistic electrons interacting with the Dirac sea. It can be seen as a mean-field approximation of Quantum Electrodynamics (QED) where photons are neglected. This paper treats the case of an electron together with the Dirac sea in the absence of any external field. Such a system is described by its one-body density matrix, an infinite rank, self-adjoint operator. The parameters of the model are the coupling constant α > 0 and the ultraviolet cut-off Λ > 0: we consider the subspace of squared integrable functions made of the functions whose Fourier transform vanishes outside the ball B(0, Λ). We prove the existence of minimizers of the BDF energy under the charge constraint of one electron and no external field provided that α, Λ-1 and α log(Λ) are sufficiently small. The interpretation is the following: in this regime the electron creates a polarization in the Dirac vacuum which allows it to bind. We then study the non-relativistic limit of such a system in which the speed of light tends to infinity (or equivalently α tends to zero) with αlog(Λ) fixed: after rescaling and translation the electronic solution tends to a Choquard-Pekar ground state.
Nuclear Ground State Properties in Strontium by Fast Beam Laser Spectroscopy
2002-01-01
Hyperfine structures and isotope shifts of strontium isotopes with A=78 to A=100 were measured by collinear fast beam laser spectroscopy. Nuclear spins, moments and changes in mean square charge radii are extracted from the data. The spins and moments of most of the odd isotopes are explained in the framework of the single particle model. The changes in mean square charge radii show a decrease with increasing neutron number below the N=50 shell closure. Above N=50 the charge radii increase regularly up to N=59 before revealing a strong discontinuity, indicating the onset of strong ground state deformation. A comparison of the droplet model shows that for the transitional isotopes below and above N=50, the zero point quadrupole motion describes part of the observed shell effect. Calculations carried out in the Hartree-Fock plus BCS model suggest an additional change in the surface region of the charge distribution at spherical shape. From these calculations it is furthermore proposed, that the isotopes $^7
Variational calculation of the ground state of closed-shell nuclei up to A =40
Lonardoni, D.; Lovato, A.; Pieper, Steven C.; Wiringa, R. B.
2017-08-01
Variational calculations of ground-state properties of 4He,16O, and 40Ca are carried out employing realistic phenomenological two- and three-nucleon potentials. The trial wave function includes two- and three-body correlations acting on a product of single-particle determinants. Expectation values are evaluated with a cluster expansion for the spin-isospin dependent correlations considering up to five-body cluster terms. The optimal wave function is obtained by minimizing the energy expectation value over a set of up to 20 parameters by means of a nonlinear optimization library. We present results for the binding energy, charge radius, one- and two-body densities, single-nucleon momentum distribution, charge form factor, and Coulomb sum rule. We find that the employed three-nucleon interaction becomes repulsive for A ≥16 . In 16O the inclusion of such a force provides a better description of the properties of the nucleus. In 40Ca instead, the repulsive behavior of the three-body interaction fails to reproduce experimental data for the charge radius and the charge form factor. We find that the high-momentum region of the momentum distributions, determined by the short-range terms of nuclear correlations, exhibits a universal behavior independent of the particular nucleus. The comparison of the Coulomb sum rules for 4He,16O, and 40Ca reported in this work will help elucidate in-medium modifications of the nucleon form factors.
Study of the Ground-State Geometry of Silicon Clusters Using Artificial Neural Networks
Directory of Open Access Journals (Sweden)
M.R. Lemes
2002-09-01
Full Text Available Theoretical determination of the ground-state geometry of Si clusters is a difficult task. As the number of local minima grows exponentially with the number of atoms, to find the global minimum is a real challenge. One may start the search procedure from a random distribution of atoms but it is probably wiser to make use of any available information to restrict the search space. Here, we introduce a new approach, the Assisted Genetic Optimization (AGO that couples an Artificial Neural Network (ANN to a Genetic Algorithm (GA. Using available information on small Silicon clusters, we trained an ANN to predict good starting points (initial population for the GA. AGO is applied to Si10 and Si20 and compared to pure GA. Our results indicate: i AGO is, at least, 5 times faster than pure GA in our test case; ii ANN training can be made very fast and successfully plays the role of an experienced investigator; iii AGO can easily be adapted to other optimization problems.
Chen, Zehua; Zhang, Du; Jin, Ye; Yang, Yang; Su, Neil Qiang; Yang, Weitao
2017-09-21
To describe static correlation, we develop a new approach to density functional theory (DFT), which uses a generalized auxiliary system that is of a different symmetry, such as particle number or spin, from that of the physical system. The total energy of the physical system consists of two parts: the energy of the auxiliary system, which is determined with a chosen density functional approximation (DFA), and the excitation energy from an approximate linear response theory that restores the symmetry to that of the physical system, thus rigorously leading to a multideterminant description of the physical system. The electron density of the physical system is different from that of the auxiliary system and is uniquely determined from the functional derivative of the total energy with respect to the external potential. Our energy functional is thus an implicit functional of the physical system density, but an explicit functional of the auxiliary system density. We show that the total energy minimum and stationary states, describing the ground and excited states of the physical system, can be obtained by a self-consistent optimization with respect to the explicit variable, the generalized Kohn-Sham noninteracting density matrix. We have developed the generalized optimized effective potential method for the self-consistent optimization. Among options of the auxiliary system and the associated linear response theory, reformulated versions of the particle-particle random phase approximation (pp-RPA) and the spin-flip time-dependent density functional theory (SF-TDDFT) are selected for illustration of principle. Numerical results show that our multireference DFT successfully describes static correlation in bond dissociation and double bond rotation.
Energy Technology Data Exchange (ETDEWEB)
T. Barnes; E.S. Swanson; C.-Y. Wong; X.-M. Xu
2003-07-29
We present numerical results for the dissociation cross sections of ground-state, orbitally- and radially-excited charmonia in collisions with light mesons. Our results are derived using the nonrelativistic quark model, so all parameters are determined by fits to the experimental meson spectrum. Examples of dissociation into both exclusive and inclusive final states are considered. The dissociation cross sections of several C=(+) charmonia may be of considerable importance for the study of heavy ion collisions, since these states are expected to be produced more copiously than the J/{psi}. The relative importance of the productions of ground-state and orbitally-excited charmed mesons in a pion-charmonium collision is demonstrated through the {radical}s-dependent charmonium dissociation cross sections.
A large-space shell-model approach to the ground state properties of sup 16 O
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Takayanagi, K. (Tokyo Denki Univ., Hatoyama, Saitama (Japan). Dept. of Mathematical Sciences); Lipparini, E. (Trento Univ. (Italy). Dipartimento di Fisica)
1991-05-23
We perform a large-space shell-model calculation of the non-local one-body density of {sup 16}O which takes into account the two-particle-two-hole correlations in the ground state. An application is done to a simultaneous study of the matter and momentum distributions and the occupation numbers of particle levels. (orig.).
Crey, Lawrence D.; Petersen, Walter A.; Christian, Hugh J., Jr.
2009-01-01
This poster reviews the program to estimate the intracloud (IC) to cloud-to-ground (CG) ratio (Z = IC/CG) of a large sample of extreme (i.e., severe) weather events over the contiguous United States (CONUS) using coincident Optical Transient Detector (OTD) [or Lightning Image Sensor (LIS)] and National Lightning Detection Network (NLDN) observations
Harbola, Varun
2011-01-01
In this paper, we accurately estimate the ground-state energy and the atomic radius of the helium atom and a helium-like Hookean atom by employing the uncertainty principle in conjunction with the variational approach. We show that with the use of the uncertainty principle, electrons are found to be spread over a radial region, giving an electron…
Magnasco, Valerio
2008-01-01
Orbital exponent optimization in the elementary ab-initio VB calculation of the ground states of H[subscript 2][superscript +], H[subscript 2], He[subscript 2][superscript +], He[subscript 2] gives a fair description of the exchange-overlap component of the interatomic interaction that is important in the bond region. Correct bond lengths and…
First-principles determination of the ground-state structure of Mg(BH4)(2)
DEFF Research Database (Denmark)
Caputo, R.; Tekin, Adem; Sikora, W.
2009-01-01
The ground-state structure of magnesium tetrahydroborate, Mg(BH4)(2), is still under debate. The experimentally and theoretically proposed structures mismatch, and even among the computationally determined structures a disagreement still exists. The main debated question is related to the lattice...... the case of Mg(BH4)(2)....
Directory of Open Access Journals (Sweden)
Stephen L. Adler
2015-03-01
Full Text Available Working with explicit examples given by the 56 representation in SU(8, and the 10 representation in SU(5, we show that symmetry breaking of a group G⊃G1×G2 by a scalar in a rank three or two antisymmetric tensor representation leads to a number of distinct modular ground states. For these broken symmetry phases, the ground state is periodic in an integer divisor p of N, where N>0 is the absolute value of the nonzero U(1 generator of the scalar component Φ that is a singlet under the simple subgroups G1 and G2. Ground state expectations of fractional powers Φp/N provide order parameters that distinguish the different phases. For the case of period p=1, this reduces to the usual Higgs mechanism, but for divisors N≥p>1 of N it leads to a modular ground state with periodicity p, implementing a discrete Abelian symmetry group U(1/Zp. This observation may allow new approaches to grand unification and family unification.
Influence of 2p-2h ground state correlations on charge distributions of doubly-closed shell nuclei
Energy Technology Data Exchange (ETDEWEB)
Waroquier, M.; Bloch, J.; Wenes, G.; Heyde, K.
1983-10-01
Ground state 2p-2h correlations are explicitly calculated in a completely self-consistent way within the framework of the Tamm-Dancoff approximation using a ''universal'' effective nucleon-nucleon interaction of the Skyrme type. Their influence on the charge distributions of /sup 16/O, /sup 40/Ca, and /sup 48/Ca is studied.
Ground-state phase diagram of an anisotropic spin-1/2 model on the triangular lattice
Luo, Qiang; Hu, Shijie; Xi, Bin; Zhao, Jize; Wang, Xiaoqun
2017-04-01
Motivated by a recent experiment on the rare-earth material YbMgGaO4 [Y. Li et al., Phys. Rev. Lett. 115, 167203 (2015), 10.1103/PhysRevLett.115.167203], which found that the ground state of YbMgGaO4 is a quantum spin liquid, we study the ground-state phase diagram of an anisotropic spin-1 /2 model that was proposed to describe YbMgGaO4. Using the density matrix renormalization-group method in combination with the exact-diagonalization method, we calculate a variety of physical quantities, including the ground-state energy, the fidelity, the entanglement entropy and spin-spin correlation functions. Our studies show that in the quantum phase diagram, there is a 120∘ phase and two distinct stripe phases. The transitions from the two stripe phases to the 120∘ phase are of the first order. However, the transition between the two stripe phases is not of the first order, which is different from its classical counterpart. Additionally, we find no evidence for a quantum spin liquid in this model. Our results suggest that additional terms may also be important to model the material YbMgGaO4. These findings will stimulate further experimental and theoretical works in understanding the quantum spin-liquid ground state in YbMgGaO4.
Ground-state properties of ordered, partially ordered, and random Cu-Au and Ni-Pt alloys
DEFF Research Database (Denmark)
Ruban, Andrei; Abrikosov, I. A.; Skriver, Hans Lomholt
1995-01-01
We have studied the ground-state properties of ordered, partially ordered, and random Cu-Au and Ni-Pt alloys at the stoichiometric 1/4, 1/2, and 3/4 compositions in the framework of the multisublattice single-site (SS) coherent potential approximation (CPA). Charge-transfer effects in the random...
Ghosh, Soumen; Sonnenberger, Andrew L; Hoyer, Chad E; Truhlar, Donald G; Gagliardi, Laura
2015-08-11
The correct description of charge transfer in ground and excited states is very important for molecular interactions, photochemistry, electrochemistry, and charge transport, but it is very challenging for Kohn-Sham (KS) density functional theory (DFT). KS-DFT exchange-correlation functionals without nonlocal exchange fail to describe both ground- and excited-state charge transfer properly. We have recently proposed a theory called multiconfiguration pair-density functional theory (MC-PDFT), which is based on a combination of multiconfiguration wave function theory with a new type of density functional called an on-top density functional. Here we have used MC-PDFT to study challenging ground- and excited-state charge-transfer processes by using on-top density functionals obtained by translating KS exchange-correlation functionals. For ground-state charge transfer, MC-PDFT performs better than either the PBE exchange-correlation functional or CASPT2 wave function theory. For excited-state charge transfer, MC-PDFT (unlike KS-DFT) shows qualitatively correct behavior at long-range with great improvement in predicted excitation energies.
Ground state analysis of XCNi{sub 3} (X=Mg, Zn, and Ga) from first-principles
Energy Technology Data Exchange (ETDEWEB)
Boutaiba, F. [Departement de Physique, Universite des Sciences et de la Technologie d' Oran, Oran, USTO (Algeria); Zaoui, A., E-mail: azaoui@polytech-lille.f [Laboratoire Genie Civil et Geo-Environnement (LGCgE, EA 4515) Lille Nord de France, Polytech' Lille, Universite des Sciences et de la Technologie de Lille, Cite Scientifique, Avenue Paul Langevin, 59655 Villeneuve D' Ascq Cedex (France); Ferhat, M. [Departement de Physique, Universite des Sciences et de la Technologie d' Oran, Oran, USTO (Algeria)
2011-01-15
The ground state properties of recent antiperovskite MgCNi{sub 3} and related systems ZnCNi{sub 3} and GaCNi{sub 3} are studied using full-potential augmented plane waves method. The obtained quantities agree well with the recent experiments and theoretical data. The band structure is dominated by the Ni d band as shown in the charge density and density of states. Besides, the effect of external pressure has been addressed.
State of the Art in Input Ground Motions for Seismic Fragility and Risk Assessment
Energy Technology Data Exchange (ETDEWEB)
Kim, Jung Han; Choi, In Kil; Kim, Min Kyu [KAERI, Daejeon (Korea, Republic of)
2016-05-15
The purpose of a Seismic Probabilistic Safety Analysis (SPSA) is to determine the probability distribution of core damage due to the potential effects of earthquakes. The SPSA is performed based on four steps, a seismic hazard analysis, a component fragility evaluation, a plant system and accident sequence analysis, and a consequence analysis. There are very different spectrum shapes in every ground motions. The structural response and the seismic load applied to equipment are greatly influenced by a spectral shape of the input ground motion. Therefore the input ground motion need to be determined under the same assumption in risk calculation. Several technic for the determination of input ground motions has developed and reviewed in this study. In this research, the methodologies of the determination of input ground motion for the seismic risk assessment are reviewed and discussed. It has developed to reduce the uncertainty in fragility curves and to remove the conservatism in risk values.
Ground beef handling and cooking practices in restaurants in eight States.
Bogard, April K; Fuller, Candace C; Radke, Vincent; Selman, Carol A; Smith, Kirk E
2013-12-01
Eating in table-service restaurants has been implicated as a risk factor for Escherichia coli O157:H7 infection. To explore this association and learn about the prevalence of risky ground beef preparation practices in restaurants, the Environmental Health Specialists Network (EHS-Net) assessed ground beef handling policies and practices in restaurants in California, Colorado, Connecticut, Georgia, Minnesota, New York, Oregon, and Tennessee. Eligible restaurants prepared and served hamburgers. EHS-Net specialists interviewed a restaurant employee with authority over the kitchen (defined as the manager) using a standard questionnaire about food safety policies, hamburger preparation policies, and use of irradiated ground beef. Interviews were followed by observations of ground beef preparation. Data from 385 restaurants were analyzed: 67% of the restaurants were independently owned and 33% were chain restaurants; 75% of the restaurants were sit down, 19% were quick service or fast food, and 6% were cafeteria or buffet restaurants. Eighty-one percent of restaurants reported determining doneness of hamburgers by one or more subjective measures, and 49% reported that they never measure the final cook temperatures of hamburgers. At least two risky ground beef handling practices were observed in 53% of restaurants. Only 1% of restaurants reported purchasing irradiated ground beef, and 29% were unfamiliar with irradiated ground beef. Differences in risky ground beef handling policies and practices were noted for type of restaurant ownership (independently owned versus chain) and type of food service style (sit down versus quick service or fast food). This study revealed the pervasiveness of risky ground beef handling policies and practices in restaurants and the need for educational campaigns targeting food workers and managers. These results highlight the importance of continued efforts to reduce the prevalence of E. coli O157:H7 in ground beef.
Energy Technology Data Exchange (ETDEWEB)
Alécio, Raphael C.; Lyra, Marcelo L. [Instituto de Física, Universidade Federal de Alagoas, 57072–970 Maceió-AL (Brazil); Strečka, Jozef [Department of Theoretical Physics and Astrophysics, Faculty of Science, P. J. Šafárik University, Park Angelinum 9, 040 01 Košice (Slovakia)
2016-11-01
The ground-state phase diagram, magnetization process and bipartite entanglement of the frustrated spin-1/2 Ising-Heisenberg and Heisenberg triangular tube (three-leg ladder) are investigated in a non-zero external magnetic field. The exact ground-state phase diagram of the spin-1/2 Ising-Heisenberg tube with Heisenberg intra-rung and Ising inter-rung couplings consists of six distinct gapped phases, which manifest themselves in a magnetization curve as intermediate plateaus at zero, one-third and two-thirds of the saturation magnetization. Four out of six available ground states exhibit quantum entanglement between two spins from the same triangular unit evidenced by a non-zero concurrence. Density-matrix renormalization group calculations are used in order to construct the ground-state phase diagram of the analogous but purely quantum spin-1/2 Heisenberg tube with Heisenberg intra- and inter-rung couplings, which consists of four gapped and three gapless phases. The Heisenberg tube shows a continuous change of the magnetization instead of a plateau at zero magnetization, while the intermediate one-third and two-thirds plateaus may be present or not in the zero-temperature magnetization curve. - Highlights: • Ground-state properties of Ising-Heisenberg and full Heisenberg spin tubes are studied. • Phases with 1/3 and 2/3 magnetization plateaus are present in both models. • We unveil the region in the parameter space on which inter-rung quantum fluctuations are relevant. • The full Heisenberg tube exhibits quantum bipartite entanglement between intra- as well as inter-rung spins.
Blank, I.; Otranto, S.; Meinema, C.; Olson, R. E.; Hoekstra, R.
2012-01-01
Single electron transfer and ionization in collisions of N5+ and Ne8+ with ground state Na(3s) and laser excited Na*(3p) are investigated both experimentally and theoretically at collision energies from 1 to 10 keV/amu, which includes the classical orbital velocity of the valence electron.
Huang, C H; Kaiser, R I; Chang, A H H
2009-11-12
The bimolecular reaction of ground state cyano radical with propylene under the condition of single collision is investigated by combining ab initio electronic structure calculations for predicting reaction paths and RRKM theory to yield rate constant for each path. The isomerization and dissociation channels for each of the seven collision complexes are characterized by utilizing the unrestricted B3LYP/cc-pVTZ level of theory and the CCSD(T)/cc-pVTZ calculations. Sifting with the facilitation of RRKM rate constants through web of ab initio paths composed of 8 collision complexes, 37 intermediates, and 12 H-, 23 H(2)-, 3 HCN-, and 4 CH(3)-dissociated products, we identify the most probable paths down to 7-9 species at collisions energies of 0 and 5 kcal/mol as the reaction mechanisms. The rate equations of the reaction mechanisms are solved numerically such that the concentration evolutions for all species involved are obtained. This study predicts that CN + C(2)H(3)CH(3) reaction via any of the seven collision complex, c1-c5, c7, and c8, would produce p1(CH(3)CHCHCN) + H, p2(CH(2)CHCH(2)CN) + H, and mostly p43(vinyl cyanide) + CH(3) for collision energy within 0-5 kcal/mol. In addition to the insertion mechanism through collision complex, the direct H-abstraction of propylene by CN radical might occur. Our investigation indicates that the barrierless and exoergic CN(X(2)Sigma(+)) + C(2)H(3)CH(3)(X(1)A') reaction would be an efficient route for the p1, p2, and p43, and likely HCN formation in cold molecular clouds and in the atmosphere of Saturn's satellite Titan.
Loco, Daniele; Polack, Étienne; Caprasecca, Stefano; Lagardère, Louis; Lipparini, Filippo; Piquemal, Jean-Philip; Mennucci, Benedetta
2016-08-09
A fully polarizable implementation of the hybrid quantum mechanics/molecular mechanics approach is presented, where the classical environment is described through the AMOEBA polarizable force field. A variational formalism, offering a self-consistent relaxation of both the MM induced dipoles and the QM electronic density, is used for ground state energies and extended to electronic excitations in the framework of time-dependent density functional theory combined with a state specific response of the classical part. An application to the calculation of the solvatochromism of the pyridinium N-phenolate betaine dye used to define the solvent ET(30) scale is presented. The results show that the QM/AMOEBA model not only properly describes specific and bulk effects in the ground state but it also correctly responds to the large change in the solute electronic charge distribution upon excitation.
Schlittler, Thiago M.; Mosseri, Rémy; Barthel, Thomas
2017-11-01
The phase diagram of the quantum dimer model on the hexagonal (honeycomb) lattice is computed numerically, extending on earlier work by Moessner, Sondhi, and Chandra. The different ground state phases are studied in detail using several local and global observables. In addition, we analyze imaginary-time correlation functions to determine ground state energies as well as gaps to the first excited states. This leads in particular to a confirmation that the intermediary so-called plaquette phase is gapped. On the technical side, we describe an efficient world-line quantum Monte Carlo algorithm with improved cluster updates that increase acceptance probabilities by taking account of potential terms of the Hamiltonian during the cluster construction. The Monte Carlo simulations are supplemented with variational computations.
Directory of Open Access Journals (Sweden)
Romig C.
2015-01-01
Full Text Available The method of relative self absorption is based on the technique of nuclear resonance fluorescence measurements. It allows for a model-independent determination of ground-state transition widths, natural level widths, and, consequently, of branching ratios to the ground state for individual excitations. Relative self–absorption experiments have been performed on the nuclei 6Li and 140Ce. In order to investigate the total level width for the 0+1, T = 1 level at 3563 keV in 6Li, a high-precision self-absorption measurement has been performed. In the case of 140Ce, self absorption has been applied for the first time to study decay widths of dipole-excited states in the energy regime of the pygmy dipole resonance.
Nature of the spin-liquid ground state of the S=1/2 Heisenberg model on the kagome lattice.
Depenbrock, Stefan; McCulloch, Ian P; Schollwöck, Ulrich
2012-08-10
We perform a density-matrix renormalization group (DMRG) study of the S=1/2 Heisenberg antiferromagnet on the kagome lattice to identify the conjectured spin liquid ground state. Exploiting SU(2) spin symmetry, which allows us to keep up to 16,000 DMRG states, we consider cylinders with circumferences up to 17 lattice spacings and find a spin liquid ground state with an estimated per site energy of -0.4386(5), a spin gap of 0.13(1), very short-range decay in spin, dimer and chiral correlation functions, and finite topological entanglement γ consistent with γ=log(2)2, ruling out gapless, chiral, or nontopological spin liquids in favor of a topological spin liquid of quantum dimension 2, with strong evidence for a gapped topological Z(2) spin liquid.
Glassy magnetic ground state and Kondo-like behaviour in Mn10FeGe8 alloy
Pramanick, S.; Dutta, P.; Majumdar, S.; Chatterjee, S.
2017-12-01
We report a detailed investigation of the ground-state magnetic properties of newly synthesized Mn10 FeGe8 alloy. The sample can be thought of being derived by substituting one Mn atom by Fe of the parent compound Mn11 Ge8 . Fe-substitution leads to a drastic change in the magnetic ground state as well as to the magneto-transport properties of the parent alloy. On cooling below 250 K, Mn10 FeGe8 undergoes a transition from paramagnetic phase to a state having significant ferromagnetic correlations. The ground state is found to be canonical spin glass (CSG) type in nature as evident from the dc magnetization and ac susceptibility measurements. Interestingly, the resistivity data shows an upturn at low temperature below about 30 K, mimicking Kondo-like behaviour. Mn10 FeGe8 turns out to be a rare example among 3d transition metal alloys, where a Kondo-like state coexists within a CSG phase.
Gacesa, Marko; Michels, H Harvey; Côté, Robin
2016-01-01
We present a theoretical analysis of optical pathways for formation of cold Ca($^1$S)Na$^+$($^1$S) molecular ions via an intermediate state. The formation schemes are based on ab initio potential energy curves and transition dipole moments calculated using effective-core-potential methods of quantum chemistry. In the proposed approach, starting from a mixture of cold trapped Ca$^+$ ions immersed into an ultracold gas of Na atoms, (NaCa)$^+$ molecular ions are photoassociated in the excited E$^{1}\\Sigma^+$ electronic state and allowed to spontaneously decay either to the ground electronic state or an intermediate state from which the population is transferred to the ground state via an additional optical excitation. By analyzing all possible pathways, we find that the efficiency of a two-photon scheme, via either B$^{1}\\Sigma^+$ or C$^{1}\\Sigma^+$ potential, is sufficient to produce significant quantities of ground state (NaCa)$^+$ molecular ions. A single-step process results in lower formation rates that wou...
U.S. Geological Survey, Department of the Interior — This data set is a national map of predicted probability of nitrate contamination of shallow ground waters based on a logistic regression (LR) model. The LR model...
Estimated mean annual natural ground-water recharge in the conterminous United States
U.S. Geological Survey, Department of the Interior — This 1-kilometer resolution raster (grid) dataset is an index of mean annual natural ground-water recharge. The dataset was created by multiplying a grid of...
U.S. Environmental Protection Agency — This EnviroAtlas dataset includes the average below ground live tree root dry biomass estimate for the Watershed Boundary Dataset (WBD) 12-digit Hydrologic Unit...
EnviroAtlas - Above Ground Live Biomass Carbon Storage for the Conterminous United States- Forested
U.S. Environmental Protection Agency — This EnviroAtlas dataset includes the average above ground live dry biomass estimate for the Watershed Boundary Dataset (WBD) 12-digit Hydrologic Unit (HUC) in kg/m...
U.S. Geological Survey, Department of the Interior — This digital data set defines the lateral boundary of the area simulated by the steady-state ground-water flow model of the Death Valley regional ground-water flow...
Theoretical investigation of the ground and low-lying excited states of nickel carbide, NiC.
Tzeli, Demeter; Mavridis, Aristides
2007-05-21
The electronic structure and bonding of 19 states of the diatomic nickel carbide (NiC) has been studied by multireference methods. Potential energy curves have been constructed for all states, whereas for the three lowest states of symmetries X (1)Sigma(+), a (3)Pi, and A (1)Pi well separated from the rest of the states, special attention was paid through the use of very large basis sets and the calculation of core-valence correlation and scalar relativistic effects. The recommended binding energies for these states are 91, 67, and 54 kcal/mol with respect to the ground state atoms. Our results in general can be considered in fair agreement with the limited experimental findings.
Energy Technology Data Exchange (ETDEWEB)
Prima, Eka Cahya [Advanced Functional Material Laboratory, Engineering Physics, Institut Teknologi Bandung (Indonesia); Computational Material Design and Quantum Engineering Laboratory, Engineering Physics, Institut Teknologi Bandung (Indonesia); International Program on Science Education, Universitas Pendidikan Indonesia (Indonesia); Yuliarto, Brian; Suyatman, E-mail: yatman@tf.itb.ac.id [Advanced Functional Material Laboratory, Engineering Physics, Institut Teknologi Bandung (Indonesia); Dipojono, Hermawan Kresno [Computational Material Design and Quantum Engineering Laboratory, Engineering Physics, Institut Teknologi Bandung (Indonesia)
2015-09-30
The aglycones of anthocyanidin dyes were previously reported to form carbinol pseudobase, cis-chalcone, and trans-chalcone due to the basic levels. The further investigations of ground and excited state properties of the dyes were characterized using density functional theory with PCM(UFF)/B3LYP/6-31+G(d,p) level in the basic solutions. However, to the best of our knowledge, the theoretical investigation of their potential photosensitizers has never been reported before. In this paper, the theoretical photovoltaic properties sensitized by dyes have been successfully investigated including the electron injections, the ground and excited state oxidation potentials, the estimated open circuit voltages, and the light harvesting efficiencies. The results prove that the electronic properties represented by dyes’ LUMO-HOMO levels will affect to the photovoltaic performances. Cis-chalcone dye is the best anthocyanidin aglycone dye with the electron injection spontaneity of −1.208 eV, the theoretical open circuit voltage of 1.781 V, and light harvesting efficiency of 56.55% due to the best HOMO-LUMO levels. Moreover, the ethanol solvent slightly contributes to the better cell performance than the water solvent dye because of the better oxidation potential stabilization in the ground state as well as in the excited state. These results are in good agreement with the known experimental report that the aglycones of anthocyanidin dyes in basic solvent are the high potential photosensitizers for dye-sensitized solar cell.
Li, Yuan
2012-09-12
Polycyclic aromatic hydrocarbons with an open-shell singlet biradical ground state are of fundamental interest and have potential applications in materials science. However, the inherent high reactivity makes their synthesis and characterization very challenging. In this work, a convenient synthetic route was developed to synthesize two kinetically blocked heptazethrene (HZ-TIPS) and octazethrene (OZ-TIPS) compounds with good stability. Their ground-state electronic structures were systematically investigated by a combination of different experimental methods, including steady-state and transient absorption spectroscopy, variable temperature NMR, electron spin resonance (ESR), superconducting quantum interfering device (SQUID), FT Raman, and X-ray crystallographic analysis, assisted by unrestricted symmetry-broken density functional theory (DFT) calculations. All these demonstrated that the heptazethrene derivative HZ-TIPS has a closed-shell ground state while its octazethrene analogue OZ-TIPS with a smaller energy gap exists as an open-shell singlet biradical with a large measured biradical character (y = 0.56). Large two-photon absorption (TPA) cross sections (σ(2)) were determined for HZ-TIPS (σ(2)max = 920 GM at 1250 nm) and OZ-TIPS (σ(2)max = 1200 GM at 1250 nm). In addition, HZ-TIPS and OZ-TIPS show a closely stacked 1D polymer chain in single crystals. © 2012 American Chemical Society.
U.S. Geological Survey, Department of the Interior — This data set represents predicted nitrate concentration in shallow, recently recharged ground water, in milligrams per liter, in the conterminous United States, and...
Decadal-scale changes of nitrate in ground water of the United States, 1988-2004.
Rupert, Michael G
2008-01-01
This study evaluated decadal-scale changes of nitrate concentrations in ground water samples collected by the USGS National Water-Quality Assessment Program from 495 wells in 24 well networks across the USA in predominantly agricultural areas. Each well network was sampled once during 1988-1995 and resampled once during 2000-2004. Statistical tests of decadal-scale changes of nitrate concentrations in water from all 495 wells combined indicate there is a significant increase in nitrate concentrations in the data set as a whole. Eight out of the 24 well networks, or about 33%, had significant changes of nitrate concentrations. Of the eight well networks with significant decadal-scale changes of nitrate, all except one, the Willamette Valley of Oregon, had increasing nitrate concentrations. Median nitrate concentrations of three of those eight well networks increased above the USEPA maximum contaminant level of 10 mg L(-1). Nitrate in water from wells with reduced conditions had significantly smaller decadal-scale changes in nitrate concentrations than oxidized and mixed waters. A subset of wells had data on ground water recharge date; nitrate concentrations increased in response to the increase of N fertilizer use since about 1950. Determining ground water recharge dates is an important component of a ground water trends investigation because recharge dates provide a link between changes in ground water quality and changes in land-use practices.
Reformulation of the covering and quantizer problems as ground states of interacting particles
Torquato, S.
2010-11-01
It is known that the sphere-packing problem and the number-variance problem (closely related to an optimization problem in number theory) can be posed as energy minimizations associated with an infinite number of point particles in d -dimensional Euclidean space Rd interacting via certain repulsive pair potentials. We reformulate the covering and quantizer problems as the determination of the ground states of interacting particles in Rd that generally involve single-body, two-body, three-body, and higher-body interactions. This is done by linking the covering and quantizer problems to certain optimization problems involving the “void” nearest-neighbor functions that arise in the theory of random media and statistical mechanics. These reformulations, which again exemplify the deep interplay between geometry and physics, allow one now to employ theoretical and numerical optimization techniques to analyze and solve these energy minimization problems. The covering and quantizer problems have relevance in numerous applications, including wireless communication network layouts, the search of high-dimensional data parameter spaces, stereotactic radiation therapy, data compression, digital communications, meshing of space for numerical analysis, and coding and cryptography, among other examples. In the first three space dimensions, the best known solutions of the sphere-packing and number-variance problems (or their “dual” solutions) are directly related to those of the covering and quantizer problems, but such relationships may or may not exist for d≥4 , depending on the peculiarities of the dimensions involved. Our reformulation sheds light on the reasons for these similarities and differences. We also show that disordered saturated sphere packings provide relatively thin (economical) coverings and may yield thinner coverings than the best known lattice coverings in sufficiently large dimensions. In the case of the quantizer problem, we derive improved upper
Anthony, S.S.
1996-01-01
The lens of fresh ground water on Ngatik Island contains about 509 million gallons of potable water. Recharge to the freshwater lens is estimated to be 990,000 gallons per day on the basis of an estimated mean annual rainfall of 160 inches. The long-term average sustainable yield is estimated to be about 280,000 gallons per day. The estimated demand for water is about 30,000 gallons per day. Shallow-vertical-tube-wells or horizontal-infiltration wells could be used to develop the freshwater lens. The effect of development on the lens can be determined by monitoring the chloride concentration of water from a network of shallow-water-table wells and deep driven wells. The ground-water resource on Ngatik can be used in conjunction with individual rainwater-catchment systems: rainwater can be used for drinking and cooking and ground water can be used for sanitary purposes. When rainwater- catchment systems fail during extended dry periods, ground water would be available to meet the total demand.
Anthony, S.S.
1996-01-01
The lens of fresh ground water on Kahlap Island contains about 21.3 million gallons of potable water. Recharge to the freshwater lens is estimated to be 125,000 gallons per day on the basis of a mean annual rainfall of 120 inches. The long-term average sustainable yield is estimated to be about 17,300 gallons per day. The estimated demand for water is about 13,500 gallons per day. Shallow-vertical-tube wells or horizontal- infiltration wells could be used to develop the freshwater lens. The effect of development on the lens can be determined by monitoring the chloride concentration of water from a network of shallow- water-table and deep driven wells. The ground- water resource on Kahlap can be used in conjunc- tion with individual rainwater-catchment systems: rainwater can be used for drinking and cooking, and ground water can be used for sanitary uses. When rainwater-catchment systems fail during extended dry periods, ground water would be available to meet the total demand.
Anthony, S.S.
1996-01-01
The lens of fresh ground water on Pingelap Island, Pingelap Atoll contains about 384 million gallons of potable water. Recharge to the freshwater lens is estimated to be 230,000 gallons per day on the basis of an average annual rainfall of 160 inches. The long-term average sustainable yield is estimated to be about 69,000 gallons per day. The estimated demand for water is about 50,000 gallons per day. Shallow-vertical-tube wells or horizontal-infiltration wells could be used to develop the freshwater lens. The effect of development on the lens can be determined by monitoring the chloride concentration of water from a network of shallow-water-table wells and deep driven wells. The ground-water resource on Pingelap can be used in conjunction with individual rainwater-catchment systems: rainwater can be used for drinking and cooking, and ground water can be used for sanitary uses. When rainwater-catchment systems fail during extended dry periods, ground water would be available to meet the total demand.
Motta, Mario; Zhang, Shiwei
2017-11-14
We address the computation of ground-state properties of chemical systems and realistic materials within the auxiliary-field quantum Monte Carlo method. The phase constraint to control the Fermion phase problem requires the random walks in Slater determinant space to be open-ended with branching. This in turn makes it necessary to use back-propagation (BP) to compute averages and correlation functions of operators that do not commute with the Hamiltonian. Several BP schemes are investigated, and their optimization with respect to the phaseless constraint is considered. We propose a modified BP method for the computation of observables in electronic systems, discuss its numerical stability and computational complexity, and assess its performance by computing ground-state properties in several molecular systems, including small organic molecules.
Tang, Yingying; Peng, Cheng; Guo, Wenbin; Wang, Jun-Feng; Su, Gang; He, Zhangzhen
2017-10-11
Search for a new geometrically frustrated lattice is a great challenge. Herein, we report on a successful synthesis of two new layered compounds BiOCu2(XO3)(SO4)(OH)·H2O [X = Te (1) and Se (2)] with a new type of geometrically frustrated lattice (i.e., the octa-kagomé lattice) between kagomé and star motifs. Magnetic measurements confirmed that 1 exhibits a spin gap ground state, while 2 possesses a typical antiferromagnetic ordering at low-temperature. Such different magnetic behaviors between two isostructural compounds are suggested to originate from a slightly structural modification induced by nonmagnetic XO3 anionic groups. Theoretical simulations suggest that the origin of gapped ground state in 1 may be due to the dimerization of Cu2+ ions, while 2 may break the limiting of such dimerization, leading to an antiferromagnetic ordering.
Feng, Jin-Shan; Tan, Lei; Gu, Huai-Qiang; Liu, Wu-Ming
2017-12-01
We theoretically analyze the ground-state cooling of an optically levitated nanosphere in the unresolved-sideband regime by introducing a coupled high-quality-factor cavity. On account of the quantum interference stemming from the presence of the coupled cavity, the spectral density of the optical force exerting on the nanosphere gets changed and then the symmetry between the heating and the cooling processes is broken. Through adjusting the detuning of a strong-dissipative cavity mode, one obtains an enhanced net cooling rate for the nanosphere. It is illustrated that the ground-state cooling can be realized in the unresolved sideband regime even if the effective optomechanical coupling is weaker than the frequency of the nanosphere, which can be understood by the picture that the effective interplay of the nanosphere and the auxiliary cavity mode brings the system back to an effective resolved regime. Besides, the coupled cavity refines the dynamical stability of the system.
Study of Ground State Wave-function of the Neutron-rich 29,30Na Isotopes through Coulomb Breakup
Rahaman, A.; Datta Pramanik, U.; Aumann, T.; Beceiro, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chatterjee, S.; Chartier, M.; De Angelis, G.; Cortina-Gil, D.; Gonzalez-Diaz, D.; Emling, H.; Diaz Fernandez, P.; Fraile, L. M.; Ershova, O.; Geissel, H.; Heil, M.; Jonson, B.; Kelic, A.; Johansson, H.; Kruecken, R.; Kroll, T.; Kurcewicz, J.; Langer, C.; Bleis, T. Le; Leifels, Y.; Munzenberg, G.; Marganiec, J.; Nociforo, C.; Najafi, A.; Panin, V.; Paschalis, S.; Pietri, S.; Plag, R.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Ray, J.; Simon, H.; Scheidenberge, C.; Typel, S.; Taylor, J.; Togano, Y.; Volkov, V.; Weick, H.; Wagner, A.; Wamers, F.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.
2014-03-01
Coulomb breakup of unstable neutron rich nuclei 29,30Na around the `island of inversion' has been studied at energy around 434 MeV/nucleon and 409 MeV/nucleon respectively. Four momentum vectors of fragments, decay neutron from excited projectile and γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence. For these nuclei, the low-lying dipole strength above one neutron threshold can be explained by direct breakup model. The analysis for Coulomb breakup of 29,30Na shows that large amount of the cross section yields the 28Na, 29Na core in ground state. The predominant ground-state configuration of 29,30Na is found to be 28Na(g.s)⊗νs1/2 and 29Na(g.s)⊗νs1/2,respectively.
Study of Ground State Wave-function of the Neutron-rich 29,30Na Isotopes through Coulomb Breakup
Directory of Open Access Journals (Sweden)
Rahaman A.
2014-03-01
Full Text Available Coulomb breakup of unstable neutron rich nuclei 29,30Na around the ‘island of inversion’ has been studied at energy around 434 MeV/nucleon and 409 MeV/nucleon respectively. Four momentum vectors of fragments, decay neutron from excited projectile and γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence. For these nuclei, the low-lying dipole strength above one neutron threshold can be explained by direct breakup model. The analysis for Coulomb breakup of 29,30Na shows that large amount of the cross section yields the 28Na, 29Na core in ground state. The predominant ground-state configuration of 29,30Na is found to be 28Na(g.s⊗νs1/2 and 29Na(g.s⊗νs1/2,respectively.
Norris, D G; Orozco, L A; Barberis-Blostein, P; Carmichael, H J; 10.1103/PhysRevA.86.053816
2012-01-01
The spontaneous creation and persistence of ground-state coherence in an ensemble of intracavity Rb atoms has been observed as a quantum beat. Our system realizes a quantum eraser, where the detection of a first photon prepares a superposition of ground-state Zeeman sublevels, while detection of a second erases the stored information. Beats appear in the time-delayed photon-photon coincidence rate (intensity correlation function). We study the beats theoretically and experimentally as a function of system parameters, and find them remarkably robust against perturbations such as spontaneous emission. Although beats arise most simply through single-atom-mediated quantum interference, scattering pathways involving pairs of atoms interfere also in our intracavity experiment. We present a detailed model which identifies all sources of interference and accounts for experimental realities such as imperfect pre-pumping of the atomic beam, cavity birefringence, and the transit of atoms across the cavity mode.
Energy Technology Data Exchange (ETDEWEB)
Harbola, Varun, E-mail: varunh@iitk.ac.in [Kendriya Vidyalaya (Central School) Indian Institute of Technology, Kanpur-208 016 (India)
2011-11-15
In this paper, we accurately estimate the ground-state energy and the atomic radius of the helium atom and a helium-like Hookean atom by employing the uncertainty principle in conjunction with the variational approach. We show that with the use of the uncertainty principle, electrons are found to be spread over a radial region, giving an electron cloud. Our calculation also shows how the Coulomb interaction between electrons affects their distribution. This leads to a physical picture of how electrons are located with respect to each other in these atoms. Finally, we also obtain through our calculations a general formula for the estimate of ground-state energy and radius of two electron atoms and ions with atomic number Z.
Sun, Yong; Ding, Zhao-Hua; Xiao, Jing-Lin
2016-07-01
On the condition of strong electron-LO phonon coupling in a RbCl quantum pseudodot (QPD), the ground state energy and the mean number of phonons are calculated by using the Pekar variational method and quantum statistical theory. The variations of the ground state energy and the mean number with respect to the temperature and the cyclotron frequency of the magnetic field are studied in detail. We find that the absolute value of the ground state energy increases (decreases) with increasing temperature when the temperature is in the lower (higher) temperature region, and that the mean number increases with increasing temperature. The absolute value of the ground state energy is a decreasing function of the cyclotron frequency of the magnetic field whereas the mean number is an increasing function of it. We find two ways to tune the ground state energy and the mean number: controlling the temperature and controlling the cyclotron frequency of the magnetic field.
The separation of vibrational coherence from ground- and excited-electronic states in P3HT film
Song, Yin
2015-06-07
© 2015 AIP Publishing LLC. Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S (λ 1, T∼ 2, λ 3)) along the population time (T∼ 2) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S (λ 1, ν∼ 2, λ 3)). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ ν∼ 2) in the rephasing beating map and at negative frequency (- ν∼ 2) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems.
Electric field control of the LaAlO3/SrTiO3 interface ground state.
Caviglia, A D; Gariglio, S; Reyren, N; Jaccard, D; Schneider, T; Gabay, M; Thiel, S; Hammerl, G; Mannhart, J; Triscone, J-M
2008-12-04
Interfaces between complex oxides are emerging as one of the most interesting systems in condensed matter physics. In this special setting, in which translational symmetry is artificially broken, a variety of new and unusual electronic phases can be promoted. Theoretical studies predict complex phase diagrams and suggest the key role of the charge carrier density in determining the systems' ground states. A particularly fascinating system is the conducting interface between the band insulators LaAlO(3) and SrTiO(3) (ref. 3). Recently two possible ground states have been experimentally identified: a magnetic state and a two-dimensional superconducting condensate. Here we use the electric field effect to explore the phase diagram of the system. The electrostatic tuning of the carrier density allows an on/off switching of superconductivity and drives a quantum phase transition between a two-dimensional superconducting state and an insulating state. Analyses of the magnetotransport properties in the insulating state are consistent with weak localization and do not provide evidence for magnetism. The electric field control of superconductivity demonstrated here opens the way to the development of new mesoscopic superconducting circuits.
Ground state of Er sup 3+ ions in ErNi sub 5 as studied by high field magnetization
Energy Technology Data Exchange (ETDEWEB)
Radwanski, R.J.; Franse, J.J.M.; Kayzel, F.E.; Marquina, C. (Van der Waals-Zeeman Lab., Univ. Amsterdam (Netherlands)); Gignoux, D. (Lab. Louis Neel, CNRS, 38 - Grenoble (France)); Szewczyk, A. (Inst. of Physics of Polish Academy of Sciences, Warszaw (Poland))
1992-03-01
By magnetization studies of single crystalline ErNi{sub 5} in magnetic fields up to 35 T, the crystal field and exchange interactions have been evaluated. The ground state of the Er{sup 3+} ion is found to be a {Gamma}{sub 9} doublet with a dominant vertical stroke{+-}15/2> contribution. The derived parameters describe the inelastic neutron scattering and specific heat results available in the literature very well. (orig.).
Huang, Wenxuan; Kitchaev, Daniil A.; Dacek, Stephen T.; Rong, Ziqin; Urban, Alexander; Cao, Shan; Luo, Chuan; Ceder, Gerbrand
2016-10-01
Lattice models, also known as generalized Ising models or cluster expansions, are widely used in many areas of science and are routinely applied to the study of alloy thermodynamics, solid-solid phase transitions, magnetic and thermal properties of solids, fluid mechanics, and others. However, the problem of finding and proving the global ground state of a lattice model, which is essential for all of the aforementioned applications, has remained unresolved for relatively complex practical systems, with only a limited number of results for highly simplified systems known. In this paper, we present a practical and general algorithm that provides a provable periodically constrained ground state of a complex lattice model up to a given unit cell size and in many cases is able to prove global optimality over all other choices of unit cell. We transform the infinite-discrete-optimization problem into a pair of combinatorial optimization (MAX-SAT) and nonsmooth convex optimization (MAX-MIN) problems, which provide upper and lower bounds on the ground state energy, respectively. By systematically converging these bounds to each other, we may find and prove the exact ground state of realistic Hamiltonians whose exact solutions are difficult, if not impossible, to obtain via traditional methods. Considering that currently such practical Hamiltonians are solved using simulated annealing and genetic algorithms that are often unable to find the true global energy minimum and inherently cannot prove the optimality of their result, our paper opens the door to resolving longstanding uncertainties in lattice models of physical phenomena. An implementation of the algorithm is available at https://github.com/dkitch/maxsat-ising.
Spin liquid ground state in the frustrated S = 1/2 square lattice compound PbVO{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Tsirlin, A. [MPI CPfS, Dresden (Germany); Dept. of Chemistry, MSU (Russian Federation); Shpanchenko, R.; Antipov, E. [Dept. of Chemistry, MSU (Russian Federation); Belik, A.; Takayama-Muromachi, E. [NIMS, Tsukuba (Japan); Rosner, H. [MPI CPfS, Dresden (Germany)
2007-07-01
The S=1/2 square lattice is known to be one of the simplest models of low-dimensional spin systems depicting the magnetic properties of many transition metal compounds like La{sub 2}CuO{sub 4}. If one considers nearest-neighbor (NN) interactions only, long-range spin order is established in the square lattice. Nevertheless, taking into account next-nearest neighbor (NNN) interactions may result in strong frustration of the spin system and give rise to unusual collinear magnetic order or spin liquid ground states. Here, we present a joint experimental and computational study of a novel layered vanadium oxide PbVO{sub 3} realizing a square lattice of magnetic V{sup +4} atoms. Our results show that in PbVO{sub 3} antiferromagnetic NN (J{sub 1}) as well as NNN (J{sub 2}) interactions are present. The J{sub 2}/J{sub 1} ratio is about 0.3 corresponding to a boundary between AFM ordered and spin liquid ground states. This conclusion is in a perfect agreement with magnetic susceptibility and specific heat measurements showing no sign of long-range spin order down to 2 K. PbVO{sub 3} is likely to be the first system showing spin liquid ground state for the frustrated S=1/2 square lattice. (orig.)
Strečka, Jozef; Richter, Johannes; Derzhko, Oleg; Verkholyak, Taras; KarÄ¾ová, Katarína
2017-06-01
The spin-1/2 Heisenberg octahedral chain with regularly alternating monomeric and square-plaquette sites is investigated using various analytical and numerical methods: variational technique, localized-magnon approach, exact diagonalization (ED), and density-matrix renormalization group (DMRG) methods. The model belongs to the class of flatband systems and it has a rich ground-state phase diagram including phases with spontaneously broken translational symmetry. Moreover, it exhibits an anomalous low-temperature thermodynamics close to continuous or discontinuous field-driven quantum phase transitions between three quantum ferrimagnetic phases, tetramer-hexamer phase, monomer-tetramer phase, localized-magnon phase, and two different spin-liquid phases. If the intraplaquette coupling is at least twice as strong as the monomer-plaquette coupling, the variational method furnishes a rigorous proof of the monomer-tetramer ground state in a low-field region and the localized-magnon approach provides exact evidence of a single magnon trapped at each square plaquette in a high-field region. In the rest of the parameter space we have numerically studied the ground-state phase diagram and magnetization process using DMRG and ED methods. It is shown that the zero-temperature magnetization curve may involve up to four intermediate plateaus at zero, one-fifth, two-fifths, and three-fifths of the saturation magnetization, while the specific heat exhibits a striking low-temperature peak in the vicinity of discontinuous quantum phase transitions.
Fujii, Keisuke; Yoshioka, Shinsuke; Isaka, Tadao; Kouzaki, Motoki
2015-03-01
We previously demonstrated the relationship between sidestepping performance and the preparatory state of ground reaction forces (GRFs). The present study investigated the effect of the preparatory state of GRFs on defensive performance in 1-on-1 subphase of basketball. Ten basketball players participated in 1-on-1 dribble game of basketball. The outcomes (penetrating and guarding) and the preparatory state of GRFs (non-weighted and weighted states, i.e. vertical GRFs below and above 120% of body weight, respectively) were assessed by separating the phases. In the non-weighted state and the weighted state to determine the outcome, the probability of successful guarding was 78.8% and 29.6%, respectively. The non-weighted state prevented delay of the defensive step in the determination phase. Both the non-weighted and weighted states, immediately before the determination phase, were likely to change to the weighted state in the determination phase; during this time, the defender's preparatory state would be destabilised, presumably by the dribbler's movement. These results revealed that the preparatory GRFs before the defensive step help to explain the outcome of the 1-on-1 subphase, and suggest a better way to prevent delaying initiation of the defensive step and thereby to guard more effectively against a dribbler.
Effective Hamiltonian of the nonrigid methanol CH{sub 3}OH molecule in the ground vibronic state
Energy Technology Data Exchange (ETDEWEB)
Burenin, A.V. [Institute of Applied Physics, Nizhnii Novgorod, (Russian Federation)
1995-11-01
For the nonrigid methanol CH{sub 3}OH molecule in the ground vibronic state, the simplest expression for the effective Hamiltonian and generators of its transformation to a reduced form is considered in an arbitrary order of perturbation theroy as a Taylor series expansion in dynamic variables on the basis of the concept of the configuration spin. Partitioning of the configuration-rotational wave functions is given according to the irreducible representations of the rotational subgroup of the symmetry group for the stationary state problem of the molecule considered in the Born-Oppenheimer approximation. 9 refs., 1 tab.
Kohn, Lucas; Tschirsich, Ferdinand; Keck, Maximilian; Plenio, Martin B.; Tamascelli, Dario; Montangero, Simone
2018-01-01
We provide evidence that randomized low-rank factorization is a powerful tool for the determination of the ground-state properties of low-dimensional lattice Hamiltonians through tensor network techniques. In particular, we show that randomized matrix factorization outperforms truncated singular value decomposition based on state-of-the-art deterministic routines in time-evolving block decimation (TEBD)- and density matrix renormalization group (DMRG)-style simulations, even when the system under study gets close to a phase transition: We report linear speedups in the bond or local dimension of up to 24 times in quasi-two-dimensional cylindrical systems.
Cluster decay of 112− 122 Ba isotopes from ground state and as an ...
Indian Academy of Sciences (India)
UNIV) of Poenaru et al and the Universal decay law (UDL) of Qi et al, and are compared with CPPM values and found to be in good agreement. A comparison of half-life for ground and excited systems reveals that probability of decay increases ...
Ground ice at the Phoenix Landing Site: Stability state and origin
Mellon, Michael T.; Arvidson, Raymond E.; Sizemore, Hanna G.; Searls, Mindi L.; Blaney, Diana L.; Cull, Selby; Hecht, Michael H.; Heet, Tabatha L.; Keller, H. Uwe; Lemmon, Mark T.; Markiewicz, Wojciech J.; Ming, Douglas W.; Morris, Richard V.; Pike, W. Thomas; Zent, Aaron P.
2009-12-01
A primary objective of the Phoenix mission was to examine the characteristics of high latitude ground ice on Mars. We report observations of ground ice, its depth distribution and stability characteristics, and examine its origins and history. High latitude ground ice was explored through a dozen trench complexes and landing thruster pits, over a range of polygon morphological provinces. Shallow ground ice was found to be abundant under a layer of relatively loose ice-free soil with a mean depth of 4.6 cm, which varied by more than 10x from trench to trench. These variations can be attributed mainly to slope effects and thermal inertia variations in the overburden soil affecting ground temperatures. The presence of ice at this depth is consistent with vapor-diffusive equilibrium with respect to a mean atmospheric water content of 3.4 × 1019 m-3, consistent with the present-day climate. Significant ice heterogeneity was observed, with two major forms: ice-cemented soil and relatively pure light toned ice. Ice-cemented soils, which comprised about 90% of the icy material exposed by trenching, are best explained as vapor deposited pore ice in a matrix supported porous soil. Light toned ice deposits represent a minority of the subsurface and are thought to consist of relatively thin near surface deposits. The origin of these relatively pure ice deposits appears most consistent with the formation of excess ice by soil ice segregation, such as would occur by thin film migration and the formation of ice lenses, needle ice, or similar ice structures.
Jin, Jingjing; Zhang, Suying; Han, Wei
2014-06-01
We investigate the transitions of ground states induced by zero momentum (ZM) coupling in pseudospin-1/2 Rashba spin-orbit coupled Bose-Einstein condensates confined in a harmonic trap. In a weak harmonic trap, the condensate presents a plane wave (PW) state, a stripe state or a spin polarized ZM state, and the particle distribution of the stripe state is weighted equally at two points in the momentum space without ZM coupling. The presence of ZM coupling induces an imbalanced particle distribution in the momentum space, and leads to the decrease of the amplitude of the stripe state. When its strength exceeds a critical value, the system experiences the transition from stripe phase to PW phase. The boundary of these two phases is shifted and a new phase diagram spanned by the ZM coupling and the interatomic interactions is obtained. The presence of ZM coupling can also achieve the transition from ZM phase to PW phase. In a strong harmonic trap, the condensate exhibits a vortex lattice state without ZM coupling. For the positive effective Rabi frequency of ZM coupling, the condensate is driven from a vortex lattice state to a vortex-free lattice state and finally to a PW state with the increase of coupling strength. In addition, for the negative effective Rabi frequency, the condensate is driven from a vortex lattice state to a stripe state, and finally to a PW state. The stripe state found in the strong harmonic trap is different from that in previous works because of its nonzero superfluid velocity along the stripes. We also discuss the influences of the ZM coupling on the spin textures, and indicate that the spin textures are squeezed transversely by the ZM coupling.
Directory of Open Access Journals (Sweden)
Dilce F. Rossetti
2003-06-01
Full Text Available The geological characterization of shallow subsurface Neogene deposits in northeastern Pará State using Ground Penetrating Radar (GPR revealed normal and reverse faults, as well as folds, not yet well documented by field studies. The faults are identified mostly by steeply-dipping reflections that sharply cut the nearby reflections causing bed offsets, drags and rollovers. The folds are recognized by reflections that are highly undulating, configuring broad concave and convex-up features that are up to 50 m wide and 80 to 90 ns deep. These deformation structures are mostly developed within deposits of Miocene age, though some of the faults might continue into younger deposits as well. Although the studied GPR sections show several diffractions caused by trees, differential degrees of moisture, and underground artifacts, the structures recorded here can not be explained by any of these ''noises''. The detailed analysis of the GPR sections reveals that they are attributed to bed distortion caused by brittle deformation and folding. The record of faults and folds are not widespread in the Neogene deposits of the Bragantina area. These GPR data are in agreement with structural models, which have proposed a complex evolution including strike-slip motion for this area from the Miocene to present.A caracterização geológica de depósitos neógenos ocorrentes em sub-superfície rasa no nordeste do Estado do Pará, usando Radar de Penetração no Solo (GPR, revelou a presença de falhas normais e reversas, bem como dobras, ainda não documentadas em estudos de campo prévios. As falhas são identificadas por reflexões inclinadas que cortam bruscamente reflexões vizinhas, causando freqüentes deslocamentos de camadas. As dobras são reconhecidas por reflexões fortemente ondulantes, configurando feições côncavas e convexas que medem até 50 m de amplitude e 80 a 90 m de profundidade. Estas estruturas deformacionais desenvolvem-se, principalmente
Ross, Kate
In the search for novel quantum states of matter, such as highly entangled Quantum Spin Liquids, ``geometrically frustrated'' magnetic lattices are essential for suppressing conventional magnetic order. In three dimensions, the pyrochlore lattice is the canonical frustrated geometry. Magnetic materials with pyrochlore structures have the potential to realize unusual phases such as ``quantum spin ice'', which is predicted to host emergent magnetic monopoles, electrons, and photons as its fundamental excitations. Even in pyrochlores that form long range ordered phases, this often occurs through unusual routes such as ``order by disorder'', in which the fluctuation spectrum dictates the preferred ordered state. The rare earth-based pyrochlore series R2Ti2O7 provides a fascinating variety of magnetic ground states. I will introduce the general anisotropic interaction Hamiltonian that has been successfully used to describe several materials in this series. Using inelastic neutron scattering, the relevant anisotropic interaction strengths can be extracted quantitatively. I will discuss this approach, and its application to two rare earth pyrochlore materials, Er2Ti2O7 and Yb2Ti<2O7, whose ground state properties have long been enigmatic. From these studies, ErTi2O7 and Yb2Ti2O7 have been suggested to be realizations of "quantum order by disorder" and "quantum spin ice", respectively. This research was supported by NSERC of Canada and the National Science Foundation.
Han, Kyu Young; Kim, Seong Keun; Eggeling, Christian; Hell, Stefan W
2010-08-11
Current far-field optical nanoscopy schemes overcome the diffraction barrier by ensuring that adjacent features assume different states upon detection. Ideally, the transition between these states can be repeated endlessly and, if performed optically, with low levels of light. Here we report such optical switching, realized by pairing the luminescent triplet and a long-lived dark state of diamond color centers, enabling their imaging with a resolution >10 times beyond the diffraction barrier (<20 nm).
Nutrients in ground water and surface water of the United States; an analysis of data through 1992
Mueller, D.K.; Hamilton, P.A.; Helsel, D.R.; Hitt, K.J.; Ruddy, B.C.
1995-01-01
related to interspersion of pasture and woodland with cropland in agricultural areas. Elevated nitrate concentrations in areas of more homogeneous cropland probably were a result of intensive nitrogen fertilizer application on large tracts of land. Certain regions of the United States seemed more vulnerable to nitrate contamination of ground water in agricultural areas. Regions of greater vulnerability included parts of the Northeast, Midwest, and West Coast. The well-drained soils, typical in these regions, have little capacity to hold water and nutrients; therefore, these soils receive some of the largest applications of fertilizer and irrigation in the Nation. The agricultural land is intensively cultivated for row crops, with little interspersion of pasture and woodland. Nutrient concentrations in surface water also were generally related to land use. Nitrate concentrations were highest in samples from sites downstream from agricultural or urban areas. However, concentrations were not as high as in ground water and rarely exceeded the drinking-water standard. Elevated concentrations of nitrate in surface water of the Northeastern United States might be related to large amounts of atmospheric deposition (acid rain). High concentrations in parts of the Midwest might be related to tile drainage of agricultural fields. Ammonia and phosphorus concentrations were highest downstream from urban areas. These concentrations generally were high enough to warrant concerns about toxicity to fish and accelerated eutrophication. Recent improvements in wastewater treatment have decreased ammonia concentrations downstream from some urban areas, but the result has been an increase in nitrate concentrations. Information on environmental factors that affect water quality is useful to identify drainage basins throughout the Nation with the greatest vulnerability for nutrient contamination and to delineate areas where ground-water or surface-water contamination is most likely to oc
Interactions between Ground State Oxygen Atoms and Molecules: O - O and O (sub2) - O (sub2)
Vanderslice, Joseph T.; Mason, Edward A.; Maisch, William G.
1960-01-01
Potential energy curves for O - O interactions corresponding to the X (sup 3) Sigma - g, 1 delta g, 1 Sigma plus g, 3 delta u, A3 Sigma plus u, 1 Sigma - u, and B3 Sigma states of O (sub 2) have been calculated from spectroscopic data by the Rydberg-Klein-Rees method. Curves for the remaining twelve states of O (sub 2) dissociating to ground state atoms have been obtained from relations derived from approximate quantum-mechanical calculations, and checked against the meager experimental information available. Two semi-independent calculations have been made, and are in good agreement with each other. The quantum-mechanical relations also lead to an approximate O (sub 2) - O (sub 2) interaction, which is consistent with interactions derived from vibrational relaxation times and from high-temperature gas viscosity data.
Exchange field effect in the crystal field ground state of CeMAl{sub 4}Si{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Chen, Kai; Strigari, Fabio; Sundermann, Martin; Severing, Andrea [University of Cologne, Cologne (Germany); Agrestini, Stefano [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Bauer, Eric D.; Sarrao, John L.; Thompson, Joe D. [Los Alamos National Laboratory, Los Alamos, NM (United States); Otero, Edwige [Synchrotron Soleil, Gif-sur-Yvette (France); Tanaka, Arata [Hiroshima University, Higashi-Hiroshima (Japan)
2016-07-01
The crystal-field ground state wave functions of the tetragonal Kondo lattice materials CeMAl{sub 4}Si{sub 2}(M = Rh, Ir and Pt), as well as the crystal-field splittings, are determined with low temperature linear polarized soft x-ray absorption spectroscopy. Surprisingly, at T < 20 K, which is far below the first excited crystal-field level at 200 K, a change in linear dichroism was observed that cannot be accounted for by population of crystal-field states. Adding an exchange field to the ionic full multiplet calculations below 20 K leads to a splitting to the ground state doublet and modification of J{sub z} admixture, thus accounting for the change in low temperature linear dichroism. The direction of the required exchange field is parallel along c-axis for the antiferromagnetic Rh and Ir compounds, and perpendicular to c-axis for ferromagnetic CePtAl{sub 4}Si{sub 2}.
Zakharenko, Olena; Motiyenko, R. A.; Aviles Moreno, Juan-Ramon; Huet, T. R.
2016-06-01
Methacrolein and methyl vinyl ketone are the two major oxidation products of isoprene emitted in the troposphere. New spectroscopic information is provided with the aim to allow unambiguous identification of these molecules, characterized by a large amplitude motion associated with the methyl top. State-of-the-art millimeter-wave spectroscopy experiments coupled to quantum chemical calculations have been performed. Comprehensive sets of molecular parameters have been obtained. The torsion-rotation-vibration effects will be discussed in detail. From the atmospheric application point of view the results provide precise ground state molecular constants essential as a foundation (by using the Ground State Combination Differences method) for the analysis of high resolution spectrum, recorded from 600 to 1600 wn. The infrared range can be then refitted using appropriate Hamiltonian parameters. The present work is funded by the French ANR through the PIA under contract ANR-11-LABX-0005-01 (Labex CaPPA), by the Regional Council Nord-Pas de Calais and by the European Funds for Regional Economic Development (FEDER).
Cazzoli, Gabriele; Cludi, Lino; Puzzarini, Cristina; Stoppa, Paolo; Pietropolli Charmet, Andrea; Tasinato, Nicola; Baldacci, Agostino; Baldan, Alessandro; Giorgianni, Santi; Wugt Larsen, René; Stopkowicz, Stella; Gauss, Jürgen
2011-02-03
A combined microwave, infrared, and computational investigation of CHBrF(2) is reported. For the vibrational ground state, measurements in the millimeter- and sub-millimeter-wave regions for CH(79)BrF(2) and CH(81)BrF(2) provided rotational and centrifugal-distortion constants up to the sextic terms as well as the hyperfine parameters (quadrupole-coupling and spin-rotation interaction constants) of the bromine nucleus. The determination of the latter was made possible by recording of spectra at sub-Doppler resolution, achieved by means of the Lamb-dip technique, and supporting the spectra analysis by high-level quantum chemical calculations at the coupled-cluster level. In this context, the importance of relativistic effects, which are of the order of 6.5% and included in the present work using second-order direct perturbation theory, needs to be emphasized for accurate predictions of the bromine quadrupole-coupling constants. The infrared measurements focused on the ν(4) fundamental band of CH(79)BrF(2). Fourier transform investigations using a synchrotron radiation source provided the necessary resolution for the observation and analysis of the rotational structure. The spectroscopic parameters of the v(4) = 1 state were found to be close to those of the vibrational ground state, indicating that the ν(4) band is essentially unaffected by perturbations.
Sandratskii, L. M.
2016-11-01
U2Pd2In is the material where the elements of the geometrical frustration of the lattice coexist with strong spin-orbit coupling (SOC). The ground state of the system is a noncollinear planar magnetic structure with orthogonal atomic magnetic moments. There are three possible physical mechanisms that can lead to this nontrivial magnetic structure: frustrated isotropic exchange interaction, Dzyaloshinskii-Morija interaction (DMI), and magnetic anisotropy. Our first-principles calculations show that in the case where the SOC is neglected, and therefore the DMI and magnetic anisotropy are absent, the ground state structure is the collinear ferromagnetic one. The leading contribution to the stabilization of the magnetically compensated configuration of orthogonal atomic moments is provided by the local magnetic anisotropy of the U moments. A weaker DMI leads to the lifting of the degeneracy between the magnetic states with different local chirality. The established hierarchy of the interactions allows us to explain the metamagnetic phase transition in the in-plane external magnetic field. The analysis of the noncollinearity of the spin and orbital moments of the same U atom appearing in the applied external field show that the trend to the antiparallel orientation of the two atomic moments following from the third Hund's rule is much stronger than the trend to the parallel orientation of the moments due to the applied external magnetic field.
Light–matter interaction in the long-wavelength limit: no ground-state without dipole self-energy
Rokaj, Vasil; Welakuh, Davis M.; Ruggenthaler, Michael; Rubio, Angel
2018-02-01
Most theoretical studies for correlated light–matter systems are performed within the long-wavelength limit, i.e., the electromagnetic field is assumed to be spatially uniform. In this limit the so-called length-gauge transformation for a fully quantized light–matter system gives rise to a dipole self-energy term in the Hamiltonian, i.e., a harmonic potential of the total dipole matter moment. In practice this term is often discarded as it is assumed to be subsumed in the kinetic energy term. In this work we show the necessity of the dipole self-energy term. First and foremost, without it the light–matter system in the long-wavelength limit does not have a ground-state, i.e., the combined light–matter system is unstable. Further, the mixing of matter and photon degrees of freedom due to the length-gauge transformation, which also changes the representation of the translation operator for matter, gives rise to the Maxwell equations in matter and the omittance of the dipole self-energy leads to a violation of these equations. Specifically we show that without the dipole self-energy the so-called ‘depolarization shift’ is not properly described. Finally we show that this term also arises if we perform the semi-classical limit after the length-gauge transformation. In contrast to the standard approach where the semi-classical limit is performed before the length-gauge transformation, the resulting Hamiltonian is bounded from below and thus supports ground-states. This is very important for practical calculations and for density-functional variational implementations of the non-relativistic QED formalism. For example, the existence of a combined light–matter ground-state allows one to calculate the Stark shift non-perturbatively.
Han, Jiande; Freel, Keith; Heaven, Michael C.
2011-06-01
We have examined state-to-state rotational and vibrational energy transfers for the vibrational levels (1010000) and (0112000) of C2H2 in the ground electronic state at ambient temperature. Measurements were made using a pulsed IR - UV double resonance technique. Total removal rate constants and state-to-state rotational energy transfer rate constants have been characterized for certain even-numbered rotational levels from J = 0 to 12 within the two vibrational modes. The measured state-to-state rotational energy transfer rate constants were fit to some energy-based empirical scaling and fitting laws, and the rate constants were found to be best reproduced by the statistical power-exponential gap law (PEGL). The measured rate constants were then further evaluated by a kinetic model which simulated the experimental spectra by solving simultaneous first order differential rate equations. Some rotationally-resolved vibrational energy transfer channels were also observed following excitation of (1010000). The vibrational relaxation channels were found to contribute less than 30% to the total removal rate constants of the measured rotational levels for both of the studied vibrational states.
Magnetic field effect on the ground-state binding energy in InGaN/GaN parabolic QWW
Energy Technology Data Exchange (ETDEWEB)
El Ghazi, Haddou, E-mail: hadghazi@gmail.com [LPS, Faculty of sciences, Dhar EL Mehrez, B.P 1796 Atlas Fez (Morocco); Specials Mathematics, CPGE Kénitra, Chakib Arsalane Street, Kénitra (Morocco); Jorio, Anouar; Zorkani, Izeddine [LPS, Faculty of sciences, Dhar EL Mehrez, B.P 1796 Atlas Fez (Morocco)
2013-07-15
Within the framework of the effective mass scheme, the ground-state binding energy of hydrogenic shallow-donor impurity in wurtzite (WZ) (In,Ga)N/GaN parabolic transversal-section quantum-well wire (PQWW) subjected to magnetic field is investigated. The finite-difference method within the quasi-one-dimensional effective potential model is used. A cylindrical QWW effective radius is introduced to describe the lateral confinement strength. The results show that: (i) the binding energy is the largest for the impurity located at a point corresponding to the largest electron probability density and (ii) it increases with increasing external magnetic field.
Orieux, Adeline; Boutari, Joelle; Barbieri, Marco; Paternostro, Mauro; Mataloni, Paolo
2014-11-24
Critical phenomena involve structural changes in the correlations of its constituents. Such changes can be reproduced and characterized in quantum simulators able to tackle medium-to-large-size systems. We demonstrate these concepts by engineering the ground state of a three-spin Ising ring by using a pair of entangled photons. The effect of a simulated magnetic field, leading to a critical modification of the correlations within the ring, is analysed by studying two- and three-spin entanglement. In particular, we connect the violation of a multipartite Bell inequality with the amount of tripartite entanglement in our ring.
Estevez Aguado, M.E.; Agramunt, J.; Rubio, B.; Tain, J.L.; Jordan, D.; Fraile, L.M.; Gelletly, W.; Frank, A.; Csatlos, M.; Csige, L.; Dombradi, Zs.; Krasznahorkay, A.; Nacher, E.; Sarriguren, P.; Borge, M.J.G.; Briz, J.A.; Tengblad, O.; Molina, F.; Moreno, O.; Kowalska, M.; Fedosseev, V.N.; Marsh, B.A.; Fedorov, D.V.; Molkanov, P.L.; Andreyev, A.N.; Seliverstov, M.D.; Burkard, K.; Huller, W.
2015-01-01
The beta decay of $^{192,190}$Pb has been studied using the total absorption technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the $^{192,190}$Pb isotopes are spherical. These results represent the first application of the shape determination method using the total absorption technique for heavy nuclei and in a region where there is considerable interest in nuclear shapes and shape effects.
Luo, Ding
2014-01-01
Polycyclic hydrocarbons (PHs) with a singlet biradical ground state have recently attracted extensive interest in physical organic chemistry and materials science. Replacing the carbon radical center in the open-shell PHs with a more electronegative nitrogen atom is expected to result in the more stable aminyl radical. In this work, two kinetically blocked stable/persistent derivatives (1 and 2) of indolo[2,3-b]carbazole, an isoelectronic structure of the known indeno[2,1-b]fluorene, were synthesized and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate biradical character (y0 = 0.269) and a small singlet-triplet energy gap (ΔES-T ≅ -1.78 kcal mol-1), while the more extended dibenzo-indolo[2,3-b]carbazole 2 exhibits a quinoidal closed-shell ground state. The difference can be explained by considering the number of aromatic sextet rings gained from the closed-shell to the open-shell biradical resonance form, that is to say, two for compound 1 and one for compound 2, which determines their different biradical characters. The optical and electronic properties of 2 and the corresponding aromatic precursors were investigated by one-photon absorption, transient absorption and two-photon absorption (TPA) spectroscopies and electrochemistry. Amphoteric redox behaviour, a short excited lifetime and a moderate TPA cross section were observed for 2, which can be correlated to its antiaromaticity and small biradical character. Compound 2 showed high reactivity to protic solvents due to its extremely low-lying LUMO energy level. Unusual oxidative dimerization was also observed for the unblocked dihydro-indolo[2,3-b]carbazole precursors 6 and 11. Our studies shed light on the rational design of persistent aminyl biradicals with tunable properties in the future. This journal
Two-particle correlations in the one-dimensional Hubbard model: a ground-state analytical solution
Vallejo, E; Espinosa, J E
2003-01-01
A solution to the extended Hubbard Hamiltonian for the case of two-particles in an infinite one-dimensional lattice is presented, using a real-space mapping method and the Green function technique. This Hamiltonian considers the on-site (U) and the nearest-neighbor (V) interactions. The method is based on mapping the correlated many-body problem onto an equivalent site-impurity tight-binding one in a higher dimensional space. In this new space we obtained the analytical solution for the ground state binding energy. Results are in agreement with the numerical solution obtained previously [1], and with those obtained in the reciprocal space [2]. (Author)
Energy Technology Data Exchange (ETDEWEB)
Mason, Peter [Laboratoire de Physique Statistique, Ecole Normale Superieure, UPMC Paris 06, Universite Paris Diderot, CNRS, 24 rue Lhomond, F-75005 Paris (France); Institut Jean Le Rond D' Alembert, UMR 7190 CNRS-UPMC, 4 place Jussieu, F-75005 Paris (France); Aftalion, Amandine [CNRS and Universite Versailles-Saint-Quentin-en-Yvelines, Laboratoire de Mathematiques de Versailles, CNRS UMR 8100, 45 avenue des Etats-Unis, F-78035 Versailles Cedex (France)
2011-09-15
We classify the ground states and topological defects of a rotating two-component condensate when varying several parameters: the intracomponent coupling strengths, the intercomponent coupling strength, and the particle numbers. No restriction is placed on the masses or trapping frequencies of the individual components. We present numerical phase diagrams which show the boundaries between the regions of coexistence, spatial separation, and symmetry breaking. Defects such as triangular coreless vortex lattices, square coreless vortex lattices, and giant skyrmions are classified. Various aspects of the phase diagrams are analytically justified thanks to a nonlinear {sigma} model that describes the condensate in terms of the total density and a pseudo-spin representation.
Splitting of ISGMR strength in the light-mass nucleus 24Mg due to ground-state deformation
Directory of Open Access Journals (Sweden)
Y.K. Gupta
2015-09-01
Full Text Available The isoscalar giant monopole resonance (ISGMR strength distribution in 24Mg has been determined from background-free inelastic scattering of 386-MeV α particles at extreme forward angles, including 0∘. The ISGMR strength distribution has been observed for the first time to have a two-peak structure in a light-mass nucleus. This splitting of ISGMR strength is explained well by microscopic theory in terms of the prolate deformation of the ground state of 24Mg.
Navarra, Angelica; Musto, Anna; Gargiulo, Anna; Petrosino, Giuseppe; Pierantoni, Giovanna Maria; Fusco, Alfredo; Russo, Tommaso; Parisi, Silvia
2016-03-31
A crucial event in the differentiation of mouse embryonic stem cells (ESCs) is the exit from the pluripotent ground state that leads to the acquisition of the 'primed' pluripotent phenotype, characteristic of the epiblast-like stem cells (EpiLCs). The transcription factors Oct4 and Otx2 play a key role in this phenomenon. In particular, Otx2 pioneers and activates new enhancers, which are silent in ESCs and which control the transcription of genes responsible for the acquisition of the EpiLC phenotype. An important point that remains to be addressed is the mechanism through which Otx2 engages the new enhancers and stably associates with them. Hmga2 is a member of the high-mobility group family of proteins, non-histone components of chromatin whose expression is high during embryogenesis and becomes low or undetectable in adults. Its high expression during embryogenesis suggests that Hmga2 fulfills important roles in development. Here, we demonstrate that Hmga2 accumulates soon after the induction of ESC differentiation. Its suppression hampers the exit of ESCs from the pluripotent ground state and their differentiation into EpiLCs. Mechanistically, Hmga2 controls the differentiation process by cooperating with Otx2 in the pioneering of new enhancers. In Hmga2 null induced pluripotent stem cells we observe that Otx2 fails to regulate its target genes upon the induction of differentiation. Hmga2 associates to Otx2-bound loci in EpiLCs, and in Hmga2 KO cells Otx2 is unable to engage and activate the new enhancers, thus indicating that Hmga2 is required for the binding of Otx2 to its cis-elements. We find that this mechanism also operates on the Hmga2 gene, which is one of the targets of Otx2, thus indicating the existence of a positive feedback loop. Our findings reveal a novel mechanism necessary for the exit of ESCs from the pluripotent ground state. Upon the induction of ESC differentiation, Otx2 alone or in combination with Oct4 engages new enhancers, which are
Lim, Zhenglong
2015-11-12
Quinoidal π-conjugated polycyclic hydrocarbons have attracted intensive research interest due to their unique optical/electronic properties and possible magnetic activity, which arises from a thermally excited triplet state. However, there is still lack of fundamental understanding on the factors that determine the electronic ground states. Herein, by using quinoidal oligo(9,10-anthryl)s, it is demonstrated that both aromatic stabilisation and steric strain release play balanced roles in determining the ground states. Oligomers with up to four anthryl units were synthesised and their ground states were investigated by electronic absorption and electron spin resonance (ESR) spectroscopy, assisted by density functional theory (DFT) calculations. The quinoidal 9,10-anthryl dimer 1 has a closed-shell ground state, whereas the tri- (2) and tetramers (3) both have an open-shell diradical ground state with a small singlet-triplet gap. Such a difference results from competition between two driving forces: the large steric repulsion between the anthryl/phenyl units in the closed-shell quinoidal form that drives the molecule to a flexible open-shell diradical structure, and aromatic stabilisation due to the gain of more aromatic sextet rings in the closed-shell form, which drives the molecule towards a contorted quinoidal structure. The ground states of these oligomers thus depend on the overall balance between these two driving forces and show chain-length dependence. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
DeWolfe, Oliver; Henriksson, Oscar; Wu, Chaolun
2017-12-01
We build a holographic model for the pairing fluctuation pseudogap phase in fermionic high temperature superconductivity/superfluidity based on the BCS-BEC crossover scenario. The pseudogap originates from incoherent Cooper pairing and has been observed in recent cold atom experiments. The strength of Cooper pairing and hence the BCS-BEC crossover is controlled by an effective 4-Fermi interaction and we argue that the double-trace deformation for charged scalar operator is a close analog in large N field theories. We employ the double-trace deformed Abelian Higgs model of holographic superconductors and propose that the incoherent fluctuations of the charged scalar in the bulk is the holographic dual of the fluctuating Cooper pairs. Using a Madelung transformation and the velocity-potential formalism, we develop a quantum fluid dynamics as an effective theory for these bulk fluctuations. The new fluid dynamics takes care of the boundary conditions required by AdS/CFT and encodes the vacuum polarization effect in curved spacetime. The pseudogap in conductivity can be related to the plasma oscillation of this bulk fluid.
Xiao, Jing-Lin
2016-11-01
We study the ground state energy and the mean number of LO phonons of the strong-coupling polaron in a RbCl quantum pseudodot (QPD) with hydrogen-like impurity at the center. The variations of the ground state energy and the mean number of LO phonons with the temperature and the strength of the Coulombic impurity potential are obtained by employing the variational method of Pekar type and the quantum statistical theory (VMPTQST). Our numerical results have displayed that [InlineMediaObject not available: see fulltext.] the absolute value of the ground state energy increases (decreases) when the temperature increases at lower (higher) temperature regime, [InlineMediaObject not available: see fulltext.] the mean number of the LO phonons increases with increasing temperature, [InlineMediaObject not available: see fulltext.] the absolute value of ground state energy and the mean number of LO phonons are increasing functions of the strength of the Coulombic impurity potential.
Positronium in crossed electric and magnetic fields: the existence of a long-lived ground state
Shertzer, J.; Ackermann, J; Schmelcher, P.
1997-01-01
It was earlier reported [PRL 78 199, (1997)] that long-lived excited states of positronium can be formed in crossed electric and magnetic fields at laboratory field strengths. Unlike the lower-lying states that are localized in the magnetically distorted Coulomb well, these long-lived states which can possess a lifetime up to many years are localized in an outer potential well that is formed for certain values of the pseudomomentum and magnetic field. The present work extends the original ana...
Ground state capture in $^{14}$N(p,$\\gamma$)$^{15}$O studied above the 259 keV resonance at LUNA
Trautvetter, H P; Bonetti, R; Broggini, C; Caciolli, A; Confortola, F; Corvisiero, P; Costantini, H; Elekes, Z; Formicola, A; Fülöp, Z; Gervino, G; Guglielmetti, A; Gyurky, Gy; Gustavino, C; Imbriani, G; Junker, M; Lemut, A; Limata, B; Marta, M; Mazzocchi, C; Menegazzo, R; Prati, P; Roca, V; Rolfs, C; Alvarez, C Rossi; Somorjai, E; Straniero, O; Strieder, F; Terrasi, F; Vezzu, S; Vomiero, A
2007-01-01
We report on a new measurement of $^{14}$N(p,$\\gamma$)$^{15}$O for the ground state capture transition at $E_p$ = 360, 380 and 400 keV, using the 400 kV LUNA accelerator. The true coincidence summing effect --the major source of error in the ground state capture determination-- has been significantly reduced by using a Clover--type gamma detector.
Theoretical grounds of internal audit in the system of state financial control in Ukraine
Directory of Open Access Journals (Sweden)
Dikan Larysa V.
2013-03-01
Full Text Available The article considers modern directions of reformation of the system of state financial control connected with introduction of the state internal financial control. It considers economic essence of the state internal financial control in the context of its components. It justifies the place of the internal audit in the system of the state internal financial control in Ukraine. It considers existing definitions of internal audit in legislative acts. It generalises views of scientists on interpretation of the “internal audit” notion. It provides definitions united in approaches. It conducts a critical analysis of generalised approaches. It offers the authors’ view on the essence of internal audit in budget institutions, which has certain positive features compared to existing ones.
Chiang, Pi-Chih
Several different theoretical methods have been developed to investigate the ground-state properties of ^3H, ^3He, and ^4He nuclei. Previously, the properties of these nuclei have been investigated using variational and hyperspherical methods. However, the Faddeev method, which yields essentially exact results has been used for A = 3 and the coupled-cluster method for mass 4. The error inherent in the hyperspherical method is not known, so the development of alternative method may be useful. In this work we have developed a set of effective operators to be used in the shell-model calculations. The m-scheme shell-model method is used in a systematic study of the binding energy and D-state probability obtained for the ground state of ^3H, ^3He, and ^4He nuclei using a variety of realistic nucleon-nucleon potentials. Since the main contribution to the binding energy comes from the ^1S_0 and ^3S_1 -^3D_1 nucleon -nucleon channels, and the main contribution to the D-state probability comes from the ^3S _1-^3D_1 tensor interaction, we will include only these channels in our calculations. Furthermore, this restriction will allow us to compare our results with the Faddeev five -channel calculations in coordinate space for ^3 H and ^3He. For the trinucleon calculations, we find that our results are in substantial agreement with those of Faddeev calculations. The difference between our results and those of Faddeev calculations is found to be between -0.38 MeV and 0.19 MeV for the triton binding energy and between -0.6% and 0.0% for the triton ground-state D-state probability. For the mass 4 calculations, we compare our results with the published results of hyperspherical, variational, and coupled-cluster calculations. The agreement between this work and that of the URBANA group (48) and Goldhammer (51) is excellent for the binding energy calculations. Our systematic study shows the binding energy (without the static Coulomb contribution) of the alpha particle to be between
Zou, Haiyuan; Zhao, Erhai; Liu, W. Vincent
2017-08-01
Motivated by the experimental realization of quantum spin models of polar molecule KRb in optical lattices, we analyze the spin 1 /2 dipolar Heisenberg model with competing anisotropic, long-range exchange interactions. We show that, by tilting the orientation of dipoles using an external electric field, the dipolar spin system on square lattice comes close to a maximally frustrated region similar, but not identical, to that of the J1-J2 model. This provides a simple yet powerful route to potentially realize a quantum spin liquid without the need for a triangular or kagome lattice. The ground state phase diagrams obtained from Schwinger-boson and spin-wave theories consistently show a spin disordered region between the Néel, stripe, and spiral phase. The existence of a finite quantum paramagnetic region is further confirmed by an unbiased variational ansatz based on tensor network states and a tensor renormalization group.
Zou, Haiyuan; Zhao, Erhai; Liu, W Vincent
2017-08-04
Motivated by the experimental realization of quantum spin models of polar molecule KRb in optical lattices, we analyze the spin 1/2 dipolar Heisenberg model with competing anisotropic, long-range exchange interactions. We show that, by tilting the orientation of dipoles using an external electric field, the dipolar spin system on square lattice comes close to a maximally frustrated region similar, but not identical, to that of the J_{1}-J_{2} model. This provides a simple yet powerful route to potentially realize a quantum spin liquid without the need for a triangular or kagome lattice. The ground state phase diagrams obtained from Schwinger-boson and spin-wave theories consistently show a spin disordered region between the Néel, stripe, and spiral phase. The existence of a finite quantum paramagnetic region is further confirmed by an unbiased variational ansatz based on tensor network states and a tensor renormalization group.
Energy Technology Data Exchange (ETDEWEB)
David R. Farley
2010-08-19
A model has been developed to calculate the ground-state rotational populations of homonuclear diatomic molecules in kinetic gases, including the effects of electron-impact excitation, wall collisions, and gas feed rate. The equations are exact within the accuracy of the cross sections used and of the assumed equilibrating effect of wall collisions. It is found that the inflow of feed gas and equilibrating wall collisions can significantly affect the rotational distribution in competition with non-equilibrating electron-impact effects. The resulting steady-state rotational distributions are generally Boltzmann for N≥3, with a rotational temperature between the wall and feed gas temperatures. The N=0,1,2 rotational level populations depend sensitively on the relative rates of electron-impact excitation versus wall collision and gas feed rates.
Energy Technology Data Exchange (ETDEWEB)
Hudson, C. E.; Ramsbottom, C. A.; Scott, M. P., E-mail: c.hudson@qub.ac.uk, E-mail: c.ramsbottom@qub.ac.uk, E-mail: p.scott@qub.ac.uk [Department of Applied Maths and Theoretical Physics, The Queen' s University of Belfast, Belfast BT7 1NN (United Kingdom)
2012-05-01
We have carried out a 29-state R-matrix calculation in order to calculate collision strengths and effective collision strengths for the electron impact excitation of S III. The recently developed parallel RMATRX II suite of codes have been used, which perform the calculation in intermediate coupling. Collision strengths have been generated over an electron energy range of 0-12 Ryd, and effective collision strength data have been calculated from these at electron temperatures in the range 1000-100,000 K. Results are here presented for the fine-structure transitions between the ground-state configurations of 3s {sup 2}3p {sup 23} P{sub 0,1,2}, {sup 1}D{sub 2}, and {sup 1} S{sub 0}, and the values given resolve a discrepancy between two previous R-matrix calculations.
Meckbach, L.; Stroucken, T.; Koch, S. W.
2018-01-01
A self-consistent scheme for the calculations of the interacting ground state and the near band-gap optical spectra of mono- and multilayer transition-metal-dichalcogenide systems is presented. The approach combines a dielectric model for the Coulomb interaction potential in a multilayer environment, gap equations for the renormalized ground state, and the Dirac-Wannier equation to determine the excitonic properties. To account for the extension of the individual monolayers perpendicular to their basic plane, an effective thickness parameter in the Coulomb interaction potential is introduced. Numerical evaluations show that the resulting finite thickness effects lead to significant modifications in the optical spectra, reproducing the experimentally observed nonhydrogenic features of the excitonic resonance series. Applying the theory for a variety of experimentally relevant configurations, a consistent description of the near band-gap optical properties is obtained all the way from monolayer to bulk. In addition to the well-known in-plane excitons, also interlayer excitons occur in multilayer systems suggesting a reinterpretation of experimental results obtained for bulk material.
Energy Technology Data Exchange (ETDEWEB)
Bonatsos, Dennis; Lenis, D.; Minkov, N.; Petrellis, D.; Raychev, P.P.; Terziev, P.A
2004-03-25
Davidson potentials of the form {beta}{sup 2}+{beta}{sub 0}{sup 4}/{beta}{sup 2}, when used in the original Bohr Hamiltonian for {gamma}-independent potentials bridge the U(5) and O(6) symmetries. Using a variational procedure, we determine for each value of angular momentum L the value of {beta}{sub 0} at which the derivative of the energy ratio R{sub L}=E(L)/E(2) with respect to {beta}{sub 0} has a sharp maximum, the collection of R{sub L} values at these points forming a band which practically coincides with the ground state band of the E(5) model, corresponding to the critical point in the shape phase transition from U(5) to O(6). The same potentials, when used in the Bohr Hamiltonian after separating variables as in the X(5) model, bridge the U(5) and SU(3) symmetries, the same variational procedure leading to a band which practically coincides with the ground state band of the X(5) model, corresponding to the critical point of the U(5) to SU(3) shape phase transition. A new derivation of the Holmberg-Lipas formula for nuclear energy spectra is obtained as a by-product.
Analysis and resolution of the ground-state degeneracy of the two-component Bose-Hubbard model.
Wang, Wei; Penna, Vittorio; Capogrosso-Sansone, Barbara
2014-08-01
We study the degeneracy of the ground-state energy E of the two-component Bose-Hubbard model and of the perturbative correction E(1). We show that the degeneracy properties of E and E(1) are closely related to the connectivity properties of the lattice. We determine general conditions under which E is nondegenerate. This analysis is then extended to investigate the degeneracy of E(1). In this case, in addition to the lattice structure, the degeneracy also depends on the number of particles present in the system. After identifying the cases in which E(1) is degenerate and observing that the standard (degenerate) perturbation theory is not applicable, we develop a method to determine the zeroth-order correction to the ground state by exploiting the symmetry properties of the lattice. This method is used to implement the perturbative approach to the two-component Bose-Hubbard model in the case of degenerate E(1) and is expected to be a valid tool to perturbatively study the asymmetric character of the Mott insulator to superfluid transition between the particle and hole side.
Energy Technology Data Exchange (ETDEWEB)
El Bassem, Y.; Oulne, M., E-mail: oulne@uca.ma
2017-01-15
In a previous work (El Bassem and Oulne (2015) ), hereafter referred to as paper I, we have investigated the ground-state properties of Nd, Ce and Sm isotopes within Hartree–Fock–Bogoliubov method with SLy5 Skyrme force in which the pairing strength has been generalized with a new proposed formula. However, that formula is more appropriate for the region of Nd. In this work, we have studied the ground-state properties of both even–even and odd Mo and Ru isotopes. For this, we have used Hartree–Fock–Bogoliubov method with SLy4 Skyrme force, and a new formula of the pairing strength which is more accurate for this region of nuclei. The results have been compared with available experimental data, the results of Hartree–Fock–Bogoliubov calculations based on the D1S Gogny effective nucleon–nucleon interaction and predictions of some nuclear models such as Finite Range Droplet Model (FRDM) and Relativistic Mean Field (RMF) theory.
Ground state energy of the δ-Bose and Fermi gas at weak coupling from double extrapolation
Prolhac, Sylvain
2017-04-01
We consider the ground state energy of the Lieb-Liniger gas with δ interaction in the weak coupling regime γ \\to 0 . For bosons with repulsive interaction, previous studies gave the expansion {{e}\\text{B}}≤ft(γ \\right)≃ γ -4{γ3/2}/3π +≤ft(1/6-1/{π2}\\right){γ2} . Using a numerical solution of the Lieb-Liniger integral equation discretized with M points and finite strength γ of the interaction, we obtain very accurate numerics for the next orders after extrapolation on M and γ. The coefficient of {γ5/2} in the expansion is found to be approximately equal to -0.001 587 699 865 505 944 989 29 , accurate within all digits shown. This value is supported by a numerical solution of the Bethe equations with N particles, followed by extrapolation on N and γ. It was identified as ≤ft(3\\zeta (3)/8-1/2\\right)/{π3} by G Lang. The next two coefficients are also guessed from the numerics. For balanced spin 1/2 fermions with attractive interaction, the best result so far for the ground state energy has been {{e}\\text{F}}≤ft(γ \\right)≃ {π2}/12-γ /2+{γ2}/6 . An analogue double extrapolation scheme leads to the value -\\zeta (3)/{π4} for the coefficient of {γ3} .
Managing United States public lands in response to climate change: a view from the ground up.
Ellenwood, Mikaela S; Dilling, Lisa; Milford, Jana B
2012-05-01
Federal land managers are faced with the task of balancing multiple uses and goals when making decisions about land use and the activities that occur on public lands. Though climate change is now well recognized by federal agencies and their local land and resource managers, it is not yet clear how issues related to climate change will be incorporated into on-the-ground decision making within the framework of multiple use objectives. We conducted a case study of a federal land management agency field office, the San Juan Public Lands Center in Durango, CO, U.S.A., to understand from their perspective how decisions are currently made, and how climate change and carbon management are being factored into decision making. We evaluated three major management sectors in which climate change or carbon management may intersect other use goals: forests, biofuels, and grazing. While land managers are aware of climate change and eager to understand more about how it might affect land resources, the incorporation of climate change considerations into everyday decision making is currently quite limited. Climate change is therefore on the radar screen, but remains a lower priority than other issues. To assist the office in making decisions that are based on sound scientific information, further research is needed into how management activities influence carbon storage and resilience of the landscape under climate change.
Finding Common Ground in Pension Reform: Lessons from the Washington State Pension System
Goldhaber, Dan; Grout, Cyrus
2014-01-01
As states and localities across the nation consider the tradeoffs between defined benefit (DB) and defined contribution (DC) pension systems, it is important to gain insight into what implications pension reforms might have on workforce composition and teachers' retirement savings behavior. Moreover, it is also important to consider that…
Aerial Detection, Ground Evaluation, and Monitoring of the Southern Pine Beetle: State Perspectives
Ronald F. Billings
2011-01-01
The southern pine beetle (SPB), is recognized as the most serious insect pest of southern pine forests. Outbreaks occur almost every year somewhere within its wide range, requiring intensive suppression efforts to minimize resource losses to Federal, State, and private forests. Effective management involves annual monitoring of SPB populations and aerial detection and...
Evaluation of ground water quality of Mubi town in Adamawa State ...
African Journals Online (AJOL)
STORAGESEVER
2008-06-03
Jun 3, 2008 ... the prevalence of epidemics of water borne disease in the area under study. MATERIAL AND METHOD. The study area (Figure 1) lies between latitude 9o 30 and 110 North of the Equator and longitude 13o and 13o 45' East of the Greenwich. Meridian. Mubi region is bounded in the north by Borno State ...
Aaron, J. J.; Tine, A.; Gaye, M. D.; Parkanyi, C.; Boniface, C.; Bieze, T. W. N.
The electronic absorption, and fluorescence excitation and emission spectra of 11 quinazolines have been measured at room temperature (298 K) in several solvents of different polarities (cyclohexane, dioxane, ethylether, chloroform, ethylacetate, 1-butanol, 2-propanol, ethanol, methanol, acetonitrile, dimethylformamide and dimethyl sulfoxide). The effects of the solvent upon the spectral properties are discussed. Experimental ground-state dipole moments were measured for quinazolines and were used in combination with the spectral results to evaluate their first excited singlet-state dipole moments by means of the solvatochromic shift method. The theoretical ground and excited singlet-state dipole moments for selected quinazolines were calculated as a vector sum of the π-component (obtained by the PPP method) and the σ-component (obtained from σ-bond moments). A reasonable agreement was observed between the experimental and the theoretical values. Excited singlet-state dipole moments are higher than the ground-state values for most quinazolines.
Sánchez-Coronilla, Antonio; Balón, Manuel; Muñoz, María A.; Hidalgo, José; Carmona, Carmen
2008-07-01
The hydrogen bonding and excited state proton transfer reactions between betacarboline, 9 H-pyrido[3,4- b]indole, BC, and 1,1,1,3,3,3-hexafluoropropan-2-ol, HFIP, have been studied in the aprotic solvents cyclohexane and toluene by absorption, steady state and time resolved fluorescence measurements. On the basis of these results and those of previous works (Refs. [A. Sánchez-Coronilla, C. Carmona, M.A. Muñoz, M. Balón, Chem. Phys., 327 (2006) 70] and [A. Sánchez-Coronilla, M. Balón, M.A. Muñoz, C. Carmona, Chem. Phys. 344 (2008) 72]) two main fundamental conclusions can be drawn on the photophysical behaviour of BC. Thus, it is shown, for the first time, that the non-cyclic double hydrogen bond complexes formed through both nitrogen atoms of BC, DHB, can suffer, in their ground state, an isomerisation process. These adducts acquire a quinoid structure in cyclohexane, but maintain a dipolar zwitterionic structure in toluene. Moreover, it is concluded that the observed large Stokes shifted emission, around 520 nm, is not due, as it has been so far generally accepted, to the emission of a BC zwitterionic phototautomer, but to the intramolecular charge transfer, ICT, excited state emissions of the DHB hydrogen bond adducts.
Ground state of the U{sub 2}Mo compound: Physical properties of the Ω-phase
Energy Technology Data Exchange (ETDEWEB)
Losada, E.L. [SIM3, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina); Garcés, J.E., E-mail: garces@cab.cnea.gov.ar [GIA, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina)
2016-10-15
Using ab initio calculations, unexpected structural instability was recently found in the ground state of the U{sub 2} Mo compound. Instead of the unstable I4/mmm and the Pmmn structures, in this work the P6/mmm (#191) space group, usually called Ω-phase, is proposed as the fundamental state. Total energy calculations using Wien2k code slightly favoured the last structure. Electronic and elastic properties are studied in this work in order to characterize the physical properties of this new phase. The stability of the Ω-phase is studied by means of its elastic constants calculation and phonon dispersion spectrum. Analysis of isotropic indices shows that the new phase is a ductile material with a minimal degree of anisotropy, suggesting that U{sub 2} Mo in the P6/mmm structure is an elastic isotropic material. Analysis of charge density, density of electronic states (DOS) and the character of the bands revealed a high level of hybridization between d-molybdenum electronic states and d- and f-uranium ones.
Ground state, electronic structure and magnetism of LaMnO{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Radwanski, R.J. E-mail: sfradwan@cyf-kr.edu.pl; Ropka, Z
2004-05-01
We argue that in LaMnO{sub 3} there exists a low-energy electronic structure originating from the atomic-like states of the strongly correlated 3d{sup 4} electronic system occurring in the Mn{sup 3+} ion. Our studies indicate that the intra-atomic spin-orbit coupling and the orbital magnetism are indispensable for the physically adequate description of electronic and magnetic properties of LaMnO{sub 3}.
Hydrogeology and ground-water quality at a land reclamation site, Neshaminy State Park, Pennsylvania
Blickwedel, Ray S.; Linn, Jeff H.
1987-01-01
At Neshaminy State park, the most important aquifer is the informally named 'Trenton gravel' of Pleistocene age, which consists of poorly sorted sand and gravel. This is underlain by less permeable crystalline rock that limits the downward movement of water. Up to 5 feet of Holocene (or perhaps Pleistocene) alluvium consisting of clay and silt was deposited above the Trenton gravel, but much of the surficial material is dredge spoil, mostly sand and silt from the Delaware River.
Ground State Structures of Boron-Rich Rhodium Boride: An Ab Initio Study
Chu, Bin-Hua; Zhao, Yuan; Yan, Jin-Liang; Li, Da
2018-01-01
Not Available Supported by the Natural Science Foundation of Shandong Province under Grant Nos ZR2016AP02, ZR2016FM38 and ZR2016EMP01, the Innovation Project of Ludong University under Grant No LB2016013, the Open Project of State Key Laboratory of Superhard Materials of Jilin University under Grant No 201605, and the National Natural Science Foundation of China under Grant Nos 11704170 and 61705097.
Taskent, Humeyra; Cho, Jae-Hyun; Raleigh, Daniel P
2008-05-02
Characterization of the transition-state ensemble and the nature of the free-energy barrier for protein folding are areas of intense activity and some controversy. A key issue that has emerged in recent years is the width of the free-energy barrier and the susceptibility of the transition state to movement. Here we report denaturant-induced and temperature-dependent folding studies of a small mixed alpha-beta protein, the N-terminal domain of L9 (NTL9). The folding of NTL9 was determined using fluorescence-detected stopped-flow fluorescence measurements conducted at seven different temperatures between 11 and 40 degrees C. Plots of the log of the observed first-order rate constant versus denaturant concentration, "chevron plots," displayed the characteristic V shape expected for two-state folding. There was no hint of deviation from linearity even at the lowest denaturant concentrations. The relative position of the transition state, as judged by the Tanford beta parameter, beta(T), shifts towards the native state as the temperature is increased. Analysis of the temperature dependence of the kinetic and equilibrium m values indicates that the effect is due to significant movement of the transition state and also includes a contribution from temperature-dependent ground-state effects. Analysis of the Leffler plots, plots of Delta G versus Delta G degrees, and their cross-interaction parameters confirms the transition-state movement. Since the protein is destabilized at high temperature, the shift represents a temperature-dependent Hammond effect. This provides independent confirmation of a recent theoretical prediction. The magnitude of the temperature-denaturant cross-interaction parameter is larger for NTL9 than has been reported for the few other cases studied. The implications for temperature-dependent studies of protein folding are discussed.
Nogawa, Tomoaki
2012-05-22
We investigate the ground state of the irrationally frustrated Josephson junction array with a controlling anisotropy parameter λ that is the ratio of the longitudinal Josephson coupling to the transverse one. We find that the ground state has one-dimensional periodicity whose reciprocal lattice vector depends on λ and is incommensurate with the substrate lattice. Approaching the isotropic point λ=1, the so-called hull function of the ground state exhibits analyticity breaking similar to the Aubry transition in the Frenkel-Kontorova model. We find a scaling law for the harmonic spectrum of the hull functions, which suggests the existence of a characteristic length scale diverging at the isotropic point. This critical behavior is directly connected to the jamming transition previously observed in the current-voltage characteristics by a numerical simulation. On top of the ground state there is a gapless continuous band of metastable states, which exhibit the same critical behavior as the ground state. © 2012 American Physical Society.
Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer
Gil, Michał; Kijak, Michał; Piwoński, Hubert; Herbich, Jerzy; Waluk, Jacek
2017-03-01
Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters. We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donor-acceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.
Non-typical fluorescence studies of excited and ground state proton and hydrogen transfer
Gil, Michał
2017-02-03
Fluorescence studies of tautomerization have been carried out for various systems that exhibit single and double proton or hydrogen translocation in various environments, such as liquid and solid condensed phases, ultracold supersonic jets, and finally, polymer matrices with single emitters.We focus on less explored areas of application of fluorescence for tautomerization studies, using porphycene, a porphyrin isomer, as an example. Fluorescence anisotropy techniques allow investigations of self-exchange reactions, where the reactant and product are formally identical. Excitation with polarized light makes it possible to monitor tautomerization in single molecules and to detect their three-dimensional orientation. Analysis of fluorescence from single vibronic levels of jet-isolated porphycene not only demonstrates coherent tunneling of two internal protons, but also indicates that the process is vibrational mode-specific. Next, we present bifunctional proton donoracceptor systems, molecules that are able, depending on the environment, to undergo excited state single intramolecular or double intermolecular proton transfer. For molecules that have donor and acceptor groups located in separate moieties linked by a single bond, excited state tautomerization can be coupled to mutual twisting of the two subunits.
Loft, N. J. S.; Kristensen, L. B.; Thomsen, A. E.; Zinner, N. T.
2016-06-01
We discuss the local density approximation approach to calculating the ground state energy of a one-dimensional Fermi gas containing a single impurity, and compare the results with exact numerical values that we have for up to 11 particles for general interaction strengths and up to 30 particles in the strongly interacting case. We also calculate the contact coefficient in the strongly interacting regime. The different theoretical predictions are compared to recent experimental results with few-atom systems. Firstly, we find that the local density approximation suffers from great ambiguity in the few-atom regime, yet it works surprisingly well for some models. Secondly, we find that the strong interaction theories quickly break down when the number of particles increase or the interaction strength decreases.
Accurate Ground-State Energies of Solids and Molecules from Time-Dependent Density-Functional Theory
DEFF Research Database (Denmark)
Olsen, Thomas; Thygesen, Kristian Sommer
2014-01-01
of the correlation hole characteristic of any local kernel. This new class of renormalized kernels gives a significantly better description of the short-range correlations in covalent bonds compared to the random phase approximation (RPA) and yields a fourfold improvement of RPA binding energies in both molecules......We demonstrate that ground-state energies approaching chemical accuracy can be obtained by combining the adiabatic-connection fluctuation-dissipation theorem with time-dependent densityfunctional theory. The key ingredient is a renormalization scheme, which eliminates the divergence...... and solids. We also consider examples of barrier heights in chemical reactions, molecular adsorption, and graphene interacting with metal surfaces, which are three examples where the RPA has been successful. In these cases, the renormalized kernel provides results that are of equal quality or even slightly...
Directory of Open Access Journals (Sweden)
Tobias Hacker
2012-04-01
Full Text Available The integral boundary layer system (IBL with spatially periodic coefficients arises as a long wave approximation for the flow of a viscous incompressible fluid down a wavy inclined plane. The Nusselt-like stationary solution of the IBL is linearly at best marginally stable; i.e., it has essential spectrum at least up to the imaginary axis. Nevertheless, in this stable case we show that localized perturbations of the ground state decay in a self-similar way. The proof uses the renormalization group method in Bloch variables and the fact that in the stable case the Burgers equation is the amplitude equation for long waves of small amplitude in the IBL. It is the first time that such a proof is given for a quasilinear PDE with spatially periodic coefficients.
Hirose, Yuhei; Miura, Shoma; Yasuda, Chitoshi; Fukumoto, Yoshiyuki
2017-08-01
Quantum Monte Carlo (QMC) simulations are performed to study ground-state properties of a mixed spin-1 and spin-1/2 Lieb-lattice Heisenberg antiferromagnet, in order to get further insight beyond the modified spin-wave (MSW) study reported in [https://doi.org/10.7566/JPSJ.86.014002" xlink:type="simple">J. Phys. Soc. Jpn. 86, 014002 (2017)]. It is confirmed that the MSW results are in good agreement with the QMC results. In particular, the scaling relation found in the MSW study, which argues that sublattice spin reductions are inversely proportional to the sublattice sizes, is observed in our QMC simulation. We present a rigorous proof for spontaneous sublattice magnetizations induced by an infinitesimal uniform magnetic field. The calculation process in the MSW theory is reexamined to clarify the mathematical structure behind the scaling relation for sublattice long-range orders.
Energy Technology Data Exchange (ETDEWEB)
Soubbotin, V.B.; Vinas, X.; Roux, C.; Danilov, P.B.; Gridnev, K.A. [Dept. d' Estructura i Constituents de la Materia, Barcelona Univ. (Spain)
1995-07-01
The ground-state properties of magic nuclei have been studied by means of the Gogny force within the Hartree-Fock Scheme using the Slater approximation for the exchange part. A similar analysis has been carried out within the semiclassical framework by considering the extended Thomas-Fermi approach for the kinetic energy density. Comparisons with the complete Hartree-Fock results are made. The ion-ion potential for two colliding nuclei has been obtained in the energy density functional and the double-folded model approaches by using self-consistent semiclassical densities calculated with the Gogny force. These potentials have been applied in the study of {sup 40}Ca-{sup 40}Ca elastic scattering. (author)
Stanke, Monika; Adamowicz, Ludwik; Kedziera, Dariusz
2013-07-01
The inclusion of the leading quantum electrodynamic energy correction is unavoidable if one aims for sub 0.01 cm-1 accuracy in the calculations of atomic and molecular spectra. The important part of the calculation of the correction is the determination of the value of the so-called Bethe logarithm (ln k 0). In this work, we examine how to construct Gaussian basis sets for such calculations. While the testing is performed for the ground state of the hydrogen atom, the results allow us to suggest how the construction of appropriate basis sets can be handled in ln k 0 calculations of atoms and molecules with more than one electron performed with explicitly correlated all-electron Gaussian functions.
Kim, Hyeong-Jin; Haines, C. R. S.; Liu, C.; Chun, Sae Hwan; Kim, Kee Hoon; Yi, H. T.; Cheong, Sang-Wook; Saxena, Siddharth S.
2017-08-01
Cs2CuCl4 is known to possess a quantum spin-liquid phase with antiferromagnetic interaction below 2.8 K. We report the observation of a new metastable magnetic phase of the triangular frustrated quantum spin system Cs2CuCl4 induced by the application of hydrostatic pressure. We measured the magnetic properties of Cs2CuCl4 following the application and release of pressure after 3 days. We observed a previously unknown ordered magnetic phase with a transition temperature of 9 K. Furthermore, the recovered sample with new magnetic ground state possesses an equivalent crystal structure to the uncompressed one with antiferromagnetic quantum spinliquid phase.
DEFF Research Database (Denmark)
Lindgård, P.-A.; Schmid, B.
1993-01-01
In the singlet ground-state systems CsFeCl3 and CsFeBr3 a large single-ion anisotropy causes a singlet ground state and a doubly degenerate doublet as the first excited states of the Fe2+ ion. In addition the magneteic interaction is anisotropic being much larger along the z axis than perpendicular...... to it. Therefore, these quasi-one-dimensional magnetic model systems are ideal to demonstrate unique correlation effects. Within the framework of the correlation theory we derive the expressions for the excitation spectrum. When a magnetic field is applied parallel to the z axis both substances have...
Energy Technology Data Exchange (ETDEWEB)
Säkkinen, Niko; Leeuwen, Robert van [Department of Physics, Nanoscience Center, University of Jyväskylä, Survontie 9, 40014 Jyväskylä (Finland); Peng, Yang [Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin (Germany); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin-Dahlem (Germany); Appel, Heiko [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin-Dahlem (Germany)
2015-12-21
We study ground-state properties of a two-site, two-electron Holstein model describing two molecules coupled indirectly via electron-phonon interaction by using both exact diagonalization and self-consistent diagrammatic many-body perturbation theory. The Hartree and self-consistent Born approximations used in the present work are studied at different levels of self-consistency. The governing equations are shown to exhibit multiple solutions when the electron-phonon interaction is sufficiently strong, whereas at smaller interactions, only a single solution is found. The additional solutions at larger electron-phonon couplings correspond to symmetry-broken states with inhomogeneous electron densities. A comparison to exact results indicates that this symmetry breaking is strongly correlated with the formation of a bipolaron state in which the two electrons prefer to reside on the same molecule. The results further show that the Hartree and partially self-consistent Born solutions obtained by enforcing symmetry do not compare well with exact energetics, while the fully self-consistent Born approximation improves the qualitative and quantitative agreement with exact results in the same symmetric case. This together with a presented natural occupation number analysis supports the conclusion that the fully self-consistent approximation describes partially the bipolaron crossover. These results contribute to better understanding how these approximations cope with the strong localizing effect of the electron-phonon interaction.
Säkkinen, Niko; Peng, Yang; Appel, Heiko; van Leeuwen, Robert
2015-12-01
We study ground-state properties of a two-site, two-electron Holstein model describing two molecules coupled indirectly via electron-phonon interaction by using both exact diagonalization and self-consistent diagrammatic many-body perturbation theory. The Hartree and self-consistent Born approximations used in the present work are studied at different levels of self-consistency. The governing equations are shown to exhibit multiple solutions when the electron-phonon interaction is sufficiently strong, whereas at smaller interactions, only a single solution is found. The additional solutions at larger electron-phonon couplings correspond to symmetry-broken states with inhomogeneous electron densities. A comparison to exact results indicates that this symmetry breaking is strongly correlated with the formation of a bipolaron state in which the two electrons prefer to reside on the same molecule. The results further show that the Hartree and partially self-consistent Born solutions obtained by enforcing symmetry do not compare well with exact energetics, while the fully self-consistent Born approximation improves the qualitative and quantitative agreement with exact results in the same symmetric case. This together with a presented natural occupation number analysis supports the conclusion that the fully self-consistent approximation describes partially the bipolaron crossover. These results contribute to better understanding how these approximations cope with the strong localizing effect of the electron-phonon interaction.
Precision measurement of the 87Rb tune-out wavelength in the hyperfine ground state F =1 at 790 nm
Schmidt, Felix; Mayer, Daniel; Hohmann, Michael; Lausch, Tobias; Kindermann, Farina; Widera, Artur
2016-02-01
We report on a precision measurement of the D line tune-out wavelength of 87 in the hyperfine ground state |F =1 ,mF=0 ,±1 > manifold at 790 nm , where the scalar ac Stark shifts of the D1 and the D2 lines cancel. This wavelength is sensitive to usually neglected contributions from vector and tensor ac Stark shifts, transitions to higher principle quantum numbers, and core electrons. The ac Stark shift is probed by Kapitza-Dirac scattering of a rubidium Bose-Einstein condensate in a one-dimensional optical lattice in free space and controlled magnetic environment. The tune-out wavelength of the magnetically insensitive mF=0 state was determined to 790.01858 (23 )n m with sub-pm accuracy. An in situ absolute polarization, and magnetic background field measurement is performed by employing the ac vector Stark shift for the mF=±1 states. Comparing our findings to theory, we get quantitative insight into atomic physics beyond commonly used two-level atom approximations or the neglect of inner shell contributions.
Energy Technology Data Exchange (ETDEWEB)
J, D.S.; DR, R. [Kuvempu University (India); Nagaraj, S. [Department of Physics, Govt. First grade college, Malleswaram, Bangalore (India); C, D.N. [Department of Physics, Vidya Vikas Institute of Engineering and Technology Mysore (India); E, S. [I D S G Govt. College Chickmagalore (India)
2014-07-01
Environmental pollution and management of water is a national and international priority today. Our environment is continuously irradiated by naturally occurring radioactive elements and their decay products found in the earth's crust. {sup 222}Rn, a noble radioactive gas produced by decay of {sup 226}Ra, is a member of the {sup 238}U series. Radon concentration measurements in water and atmosphere are necessary to understand the effect of {sup 222}Rn on human health. Epidemiological studies reveal that the exposure to radon and its progeny is the one of the main causes of lung cancer after smoking. The high concentration of radon in ground water poses a potential health risks in two ways by inhalation and ingestion. In the present study, the radon concentration in indoor air atmosphere and in drinking water have been determined by collecting various drinking water samples from bore well, tank, tap and river water from different locations in granite regions of Karnataka state and were estimated by using Solid State Nuclear Track Detector (SSNTD) technique and Emanometry technique. The radon concentration in indoor atmosphere is depends mainly on radon emanation from ground water used for domestic purposes, ventilation condition, type of building materials used for construction. The present study highlights the variation of indoor radon concentration with water used for different purposes and estimates the dose to the publics of this study area. The estimated total equivalent effective dose is higher than the global average. According to US EPA and WHO report majority of the drinking water samples and their radon concentration exceeds the reference levels. Document available in abstract form only. (authors)
Acceleration of a ground-state reaction by selective femtosecond-infrared-laser-pulse excitation
Stensitzki, Till; Yang, Yang; Kozich, Valeri; Ahmed, Ashour A.; Kössl, Florian; Kühn, Oliver; Heyne, Karsten
2018-02-01
Infrared (IR) excitation of vibrations that participate in the reaction coordinate of an otherwise thermally driven chemical reaction are believed to lead to its acceleration. Attempts at the practical realization of this concept have been hampered so far by competing processes leading to sample heating. Here we demonstrate, using femtosecond IR-pump IR-probe experiments, the acceleration of urethane and polyurethane formation due to vibrational excitation of the reactants for 1:1 mixtures of phenylisocyanate and cyclohexanol, and toluene-2,4-diisocyanate and 2,2,2-trichloroethane-1,1-diol, respectively. We measured reaction rate changes upon selective vibrational excitation with negligible heating of the sample and observed an increase of the reaction rate up to 24%. The observation is rationalized using reactant and transition-state structures obtained from quantum chemical calculations. We subsequently used IR-driven reaction acceleration to write a polyurethane square on sample windows using a femtosecond IR pulse.
Nitrogen Dioxide Trend over the United States: the View from the Ground, the View from Space
Lamsal, Lok N.; Duncan, Bryan N.; Yoshida, Yasuko; Krotkov, Nickolay A.
2014-01-01
Emissions of nitrogen oxides (NOx) are decreasing over the US due to environmental policies and technological change. We use observations of tropospheric nitrogen dioxide (NO2) columns from the Ozone Monitoring Instrument (OMI) satellite instrument and surface NO2 in-situ measurements from the air quality system (AQS) to quantify the trends, and to establish the relationship between the trends in tropospheric column and surface concentration. Both observations show substantial downward trends from 2005 to 2013, with an average reduction of 35 percent according to OMI and 38 percent according to AQS. The annual reduction rates are largest in 2005-2009: -6.2 percent per year and -7 percent per year observed by OMI and AQS, respectively. We examine various factors affecting the estimated trend in OMI NO2 columns and in-situ NO2 observations. An improved understanding of trend offers valuable insights about effectiveness of emission reduction regulations on state and federal level.
Variational calculations for ground state properties of liquid 3He injected in a carbon nanotube
Bordbar, G. H.; Rastkhadiv, M. A.
2017-09-01
Liquid 3He injected in a carbon nanotube is of high interests due to different behavior of the liquid helium in the quasi-one-dimensional systems. In this work, a variational approach has been performed to calculate some thermodynamic properties of this quantum system. In order to do so, a single-walled carbon nanotube containing liquid 3He is considered, applying the Lennard-Jones and Stan-Cole potentials for 3He-3He and 3He-C interactions, respectively. Finally the total energy, equation of state and incompressibility of the system have been calculated. Our calculations show the high values for the incompressibility at high densities, especially for high radii.
Yedukondalu, N.; Vaitheeswaran, G.
2014-06-01
Silver fulminate (AgCNO) is a primary explosive, which exists in two polymorphic phases, namely, orthorhombic (Cmcm) and trigonal (Rbar{3}) forms at ambient conditions. In the present study, we have investigated the effect of pressure and temperature on relative phase stability of the polymorphs using planewave pseudopotential approaches based on Density Functional Theory (DFT). van der Waals interactions play a significant role in predicting the phase stability and they can be effectively captured by semi-empirical dispersion correction methods in contrast to standard DFT functionals. Based on our total energy calculations using DFT-D2 method, the Cmcm structure is found to be the preferred thermodynamic equilibrium phase under studied pressure and temperature range. Hitherto Cmcm and Rbar{3} phases denoted as α- and β-forms of AgCNO, respectively. Also a pressure induced polymorphic phase transition is seen using DFT functionals and the same was not observed with DFT-D2 method. The equation of state and compressibility of both polymorphic phases were investigated. Electronic structure and optical properties were calculated using full potential linearized augmented plane wave method within the Tran-Blaha modified Becke-Johnson potential. The calculated electronic structure shows that α, β phases are indirect bandgap insulators with a bandgap values of 3.51 and 4.43 eV, respectively. The nature of chemical bonding is analyzed through the charge density plots and partial density of states. Optical anisotropy, electric-dipole transitions, and photo sensitivity to light of the polymorphs are analyzed from the calculated optical spectra. Overall, the present study provides an early indication to experimentalists to avoid the formation of unstable β-form of AgCNO.
Yedukondalu, N; Vaitheeswaran, G
2014-06-14
Silver fulminate (AgCNO) is a primary explosive, which exists in two polymorphic phases, namely, orthorhombic (Cmcm) and trigonal (R3) forms at ambient conditions. In the present study, we have investigated the effect of pressure and temperature on relative phase stability of the polymorphs using planewave pseudopotential approaches based on Density Functional Theory (DFT). van der Waals interactions play a significant role in predicting the phase stability and they can be effectively captured by semi-empirical dispersion correction methods in contrast to standard DFT functionals. Based on our total energy calculations using DFT-D2 method, the Cmcm structure is found to be the preferred thermodynamic equilibrium phase under studied pressure and temperature range. Hitherto Cmcm and R3 phases denoted as α- and β-forms of AgCNO, respectively. Also a pressure induced polymorphic phase transition is seen using DFT functionals and the same was not observed with DFT-D2 method. The equation of state and compressibility of both polymorphic phases were investigated. Electronic structure and optical properties were calculated using full potential linearized augmented plane wave method within the Tran-Blaha modified Becke-Johnson potential. The calculated electronic structure shows that α, β phases are indirect bandgap insulators with a bandgap values of 3.51 and 4.43 eV, respectively. The nature of chemical bonding is analyzed through the charge density plots and partial density of states. Optical anisotropy, electric-dipole transitions, and photo sensitivity to light of the polymorphs are analyzed from the calculated optical spectra. Overall, the present study provides an early indication to experimentalists to avoid the formation of unstable β-form of AgCNO.
The strong interaction shift and width of the ground state of pionic hydrogen
Energy Technology Data Exchange (ETDEWEB)
Sigg, D. [Eidgenoessische Technische Hochschule, Villigen (Switzerland). Inst. fuer Teilchenphysik; Badertscher, A. [Eidgenoessische Technische Hochschule, Villigen (Switzerland). Inst. fuer Teilchenphysik; Bogdan, M. [Eidgenoessische Technische Hochschule, Villigen (Switzerland). Inst. fuer Teilchenphysik; Goudsmit, P.F.A. [Eidgenoessische Technische Hochschule, Villigen (Switzerland). Inst. fuer Teilchenphysik; Leisi, H.J. [Eidgenoessische Technische Hochschule, Villigen (Switzerland). Inst. fuer Teilchenphysik; Schroeder, H.-C. [Eidgenoessische Technische Hochschule, Villigen (Switzerland). Inst. fuer Teilchenphysik; Zhao, Z.G. [Eidgenoessische Technische Hochschule, Villigen (Switzerland). Inst. fuer Teilchenphysik; Chatellard, D. [Institut de Physique de l`Universite de Neuchatel, 2000 Neuchatel (Switzerland); Egger, J.-P. [Institut de Physique de l`Universite de Neuchatel, 2000 Neuchatel (Switzerland); Jeannet, E. [Institut de Physique de l`Universite de Neuchatel, 2000 Neuchatel (Switzerland); Aschenauer, E.C. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Gabathuler, K. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Simons, L.M. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Rusi El Hassani, A.J. [Ecole Mohammadia d`Ingenieurs, Rabat (Morocco)
1996-11-18
The 3p-1s transition in pionic hydrogen was investigated with a high-resolution crystal spectrometer system. From the precisely measured transition energy, together with the (calculated) electromagnetic energy, the strong interaction shift of the 1s state was obtained as {epsilon}{sub 1s} = -7.127 {+-}0.028 (stat.) {+-}0.036 (syst.) eV (attractive). From the natural line width, measured for the first time, we determine the decay width of the 1s state: {Gamma}{sub 1s}{sup (decay)} = 0.97 {+-}0.10 (stat.) {+-}0.05 (syst.) eV. With the recently calculated electromagnetic corrections the s-wave scattering lengths of an isospin symmetric strong interaction are deduced. The scattering length for elastic scattering of a negative pion on a proton is a{sup h}{sub {pi}{sup -}p{yields}{pi}{sup -}p} = 0.0885 {+-}0.0003 (stat.) {+-}0.0006 (syst.) m{sub {pi}}{sup -1}. The scattering length for single charge exchange is found to be a{sup h}{sub {pi}{sup -}p{yields}{pi}{sup 0}n} = -0.136 {+-}0.007 (stat.) {+-}0.003 (syst.) m{sub {pi}}{sup -1}. The experiment was performed at the Paul Scherrer Institute (PSI) in Switzerland. A focussing crystal spectrometer with an array of bent crystals, the cyclotron trap (a magnetic system designed to increase the particle stop density) and a CCD (charge-coupled device) detector system were employed. The results from the pionic hydrogen experiment - together with those from the pionic deuterium experiment - were used to test the isospin symmetry of the strong interaction. The present data are still consistent with isospin symmetry. (orig.).
Photochemical formation of HCO and CH3 on the ground S0 (1A') state of CH3CHO.
Heazlewood, Brianna R; Rowling, Steven J; Maccarone, Alan T; Jordan, Meredith J T; Kable, Scott H
2009-02-07
The dynamics of the photodissociation of CH(3)CHO into CH(3) + HCO products have been investigated at energies between 30,953 and 31,771 cm(-1), spanning the threshold for radical production on the triplet (T(1)) surface. A barrierless pathway to CH(3) + HCO radical products formed on the ground state (S(0)) surface was discovered and established to be an important reaction channel in acetaldehyde photodissociation throughout this wavelength range. HCO laser induced fluorescence (LIF) spectra recorded from CH(3)CHO dissociated above and below the T(1) barrier energy are quite different; HCO produced on S(0) yields a more congested LIF spectrum with sharp rotational transitions, while HCO formed on the T(1) surface displays fewer, more intense, Doppler-broadened lines. These differences have been further explored in the populations of the HCO K(a) = 1 doublets. Despite the upper and lower levels being almost isoenergetic, HCO formed on T(1) preferentially populates the upper K(c) state due to the geometry of the T(1) transition state structure. In contrast, HCO formed on S(0) produces equal population in each of the upper and lower K(a) = 1 components. Product state distributions (PSDs) showed that HCO formed on S(0) is born with an approximately statistical distribution of population in the available product states, modeled well by phase space theory. HCO formed on the T(1) surface, in contrast, has a PSD that can be characterized as arising from "impulsive" dynamics. Previous discrepancies in the height of the T(1) barrier are discussed following the observation that, once the T(1) channel is energetically accessible, there is competition between the S(0) and T(1) pathways, with the dominance of the triplet channel increasing with increasing photolysis energy.
Killen, R.
1977-01-01
There are six cases considered: (1) no updates made during the flight, (2) one ground update in the vertical components only at the first practice separation minus 15 minutes, (3) one ground update in all components at the first practice separation minus 5 minutes, (4) updates 2 and 3 applied successively, (5) Case 4 plus an update in all components at the second separation attempt minus 3 minutes, and (6) one ground update at first separation attempt minus 5 minutes and a second update at second separation minus two minutes. The mission control simulation program, GROPER, was run using as radar input a tape containing radar derived state vectors for the trajectory.
A search for the ground state structure and the phase stability of tantalum pentoxide.
Pérez-Walton, S; Valencia-Balvín, C; Padilha, A C M; Dalpian, G M; Osorio-Guillén, J M
2016-01-27
Tantalum pentoxide (Ta2O5) is a wide-gap semiconductor that presents good catalytic and dielectric properties, conferring to this compound promising prospective use in a variety of technological applications. However, there is a lack of understanding regarding the relations among its crystalline phases, as some of them are not even completely characterized and there is currently no agreement about which models better explain the crystallographic data. Additionally, its phase diagram is unknown. In this work we performed first-principles density functional theory calculations to study the structural properties of the different phases and models of Ta2O5, the equation of state and the zone-centered vibrational frequencies. From our results, we conclude that the phases that are built up from only distorted octahedra instead of combinations with pentagonal and/or hexagonal bipyramids are energetically more favorable and dynamically stable. More importantly, this study establishes that, given the pressure range considered, the B-phase is the most favorable structure and there is no a crystallographic phase transition to another phase at high-pressure. Additionally, for the equilibrium volume of the B-phase and the λ-model, the description of the electronic structure and optical properties were performed using semi-local and hybrid functionals.
Directory of Open Access Journals (Sweden)
Seán M. Meenehan
2015-10-01
Full Text Available Using pulsed optical excitation and read-out along with single-phonon-counting techniques, we measure the transient backaction, heating, and damping dynamics of a nanoscale silicon optomechanical crystal cavity mounted in a dilution refrigerator at a base temperature of T_{f}≈11 mK. In addition to observing a slow (approximately 740-ns turn-on time for the optical-absorption-induced hot-phonon bath, we measure for the 5.6-GHz “breathing” acoustic mode of the cavity an initial phonon occupancy as low as ⟨n⟩=0.021±0.007 (mode temperature T_{min}≈70 mK and an intrinsic mechanical decay rate of γ_{0}=328±14 Hz (Q_{m}≈1.7×10^{7}. These measurements demonstrate the feasibility of using short pulsed measurements for a variety of quantum optomechanical applications despite the presence of steady-state optical heating.
The ground state properties of In(Ga)As/GaAs low strain quantum dots
Energy Technology Data Exchange (ETDEWEB)
Pieczarka, Maciej, E-mail: maciej.pieczarka@pwr.edu.pl; Sęk, Grzegorz
2016-08-15
We present theoretical studies on the confined states in low-strain In(Ga)As quantum dots (QDs). The 8-band k·p model together with the continuum elasticity theory and piezoelectric fields were employed to calculate the potential and confined electron and hole eigenstates. We focused on low-indium-content QDs with distinct in-plane asymmetry, which are naturally formed in the low strain regime of the Stranski-Krastanow growth mode. It has been found that the naturally thick wetting layer together with piezoelectric potential affect the total confinement potential to such extent that the hole eigenstates can get the spatial in-plane orientation orthogonal to the main axis of the dot elongation. This can influence both, qualitatively and quantitatively, many of the electronic and optical properties, as e.g. the polarization selection rules for the optical transition or the transitions oscillator strength. Eventually, importance of the degree of the shape asymmetry or the dots’ size, and differences between the low-strain (low-In-content) QDs and pure InAs dots formed in high strain conditions are discussed.
Directory of Open Access Journals (Sweden)
Orakwe
2015-08-01
Full Text Available Abstract The chemometric data mining techniques using principal factor analysis PFA and hierarchical cluster analysis CA was employed to evaluate and to examine the borehole characteristics of geological formations of Enugu State of Nigeria to determine the latent structure of the borehole characteristics and to classify 9 borehole parameters from 49 locations into borehole groups of similar characteristics. PFA extracted three factors which accounted for a large proportion of the variation in the data 77.305 of the variance. Out of nine parameters examined the first PFA had the highest number of variables loading on a single factor where four borehole parameters borehole depth borehole casing static water level and dynamic water level loaded on it with positive coefficient as the most significant parameters responsible for variation in borehole characteristics in the study. The CA employed in this study to identified three clusters. The first cluster delineated stations that characterise Awgu sandstone geological formation while the second cluster delineated Agbani sandstone geological formation. The third cluster delineated Ajali sandstone formation. The CA grouping of the borehole parameters showed similar trend with PFA hence validating the efficiency of chemometric data mining techniques in grouping of variations in the borehole characteristics in the geological zone of the study area.
Ilyushin, V.; Armieieva, Iuliia; Dorovskaya, Olga; Pogrebnyak, Mykola; Krapivin, Igor; Alekseev, E. A.; Margulès, L.; Motiyenko, R. A.; Kwabia Tchana, F.; Jabri, Atef; Manceron, Laurent; Bauerecker, Sigurd; Maul, Christof
2017-06-01
A new study of the dimethylsulfide ((CH_{3})_{2}S) spectrum is reported. The new measurements have been carried out using the Kharkiv spectrometer in the Institute of Radio Astronomy of NASU (Ukraine) and using the Lille spectrometer in the PhLAM laboratory (France). The new millimeter and submillimeter wave measurements cover the frequency range from 49 GHz to 660 GHz. The rotational transitions belonging to the three lowest torsional states of the molecule as well as the new assignments in the FIR torsional band (AILES beamline of the synchrotron SOLEIL) and the microwave data available in the literature have been analyzed using recently developed model for the molecules with two equivalent methyl rotors and C_{2v} symmetry at equilibrium (PAM_C2v_2tops program). In the talk the details of this new study will be discussed. This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P686). A. Jabri, V. Van, H. V. L. Nguyen, H. Mouhib, F. Kwabia Tchana , L. Manceron , W. Stahl, I. Kleiner, A&A 589, A127 (2016). Ilyushin V. V., Hougen J. T. J. Mol. Spectrosc. 289 (2013) 41-49.
Ribeiro Guevara, S
2001-01-01
determine, by this method, the production cross section for the ground state even in those cases where the assumption that one of the states has decayed completely, cannot be warranted.In cases where the ground state half life is much longer than that of the isomeric state, when employing direct methods, it is only possible to determine the sum cross section for the production of both states; therefore, if the metastable production cross section is known, then it is possible to determine, by subtraction, the ground state production cross section.When using the straight-line method, both cross sections can be determined separately.The main limitation of the method is the need to measure the g emission associated to the ground state decay at different time intervals.A parametric analysis of the equations associated to the method shows that under certain conditions it is not possible to apply the method, while under other conditions the method delivers optimum results.The method was applied to the study of four ...
Hörner, Gerald; Hug, Gordon L; Pogocki, Dariusz; Filipiak, Piotr; Bauer, Walter; Grohmann, Andreas; Lämmermann, Anica; Pedzinski, Tomasz; Marciniak, Bronislaw
2008-01-01
The formation of head-to-tail contacts in de novo synthesized benzophenone/tyrosine dyads, bp logical sum Tyr, was probed in the ground and excited triplet state by NMR techniques and laser flash photolysis, respectively. The high affinity of triplet-excited ketones towards phenols was used to trace the geometric demands for high reactivity in the excited state. A retardation effect on the rates with increasing hydrogen-bond-acceptor ability of the solvent is correlated with ground-state masking of the phenol. In a given solvent the efficiencies of the intramolecular hydrogen-atom-transfer reaction depend strongly on the properties of the linker: rate constants for the intramolecular quenching of the triplet state cover the range of 10(5) to 10(8) s(-1). The observed order of reactivity correlates to a) the probability of close contacts (from molecular-dynamics simulations) and b) the extent of the electronic overlap between the pi systems of the donor and acceptor moieties (from NMR). A broad survey of the NMR spectra in nine different solvents showed that head-to-tail interactions between the aromatic moieties of the bp logical sum Tyr dyads already exist in the ground state. Favourable aromatic-aromatic interactions in the ground state appear to correspond to high excited-state reactivity.
Directory of Open Access Journals (Sweden)
Omaka Ndukaku Omaka
2015-01-01
Full Text Available This study evaluated the hydrogeochemical attributes and quality of groundwater resources in Ngbo, Ohaukwu Area Council of Ebonyi State, Nigeria in order to determine whether boreholes in the area were suitable for potable uses. Eleven groundwater samples were collected from hand-dug boreholes between February and March, 2013. The physiochemical parameters of the samples were then analyzed to determine electrical conductivity, total dissolved solids, total alkalinity, major cations and anions, and trace metals. The quality of these characteristics was evaluated by comparing them to the Nigerian Institute of Standards, the Bureau of Indian Standards and the World Health Organization standards for drinking water quality. Mass abundance of the major ions was in the order of Mg2+ > Ca2+ for cations, Cl- > SO4 2 - > NO3 - > PO4 3 - for anions and Fe > As > Mn > Cu > Zn > Cr > Ni > Pb > Cd for trace metals. Correlation analysis revealed both positive and negative correlations among the parameters. Also, one-way ANOVA tests revealed that no significant differences existed between physiochemical parameters (F = 1.004 < Fcrit =1.977, major cations and anions (F =0.547 < Fcrit =2.008 and trace metals (F = 0.772 < Fcrit = 1.940 regardless of the sampling location. Groundwater in the area was generally hard, alkaline and highly mineralized, making it unsuitable for drinking in some places due to high total hardness and TDS; but it was generally suitable for irrigation purposes. It is recommended that boreholes be flushed regularly to aid in the removal of mineralized deposits, and that regular hydrogeochemical studies be conducted in order to detect future deterioration of water quality
Johnson, Jeremy A; Kim, Kilyoung; Mayhew, Maurine; Mitchell, Deborah G; Sevy, Eric T
2008-03-27
Relaxation of highly vibrationally excited pyridine (C5NH5) by collisions with carbon dioxide has been investigated using diode laser transient absorption spectroscopy. Vibrationally hot pyridine (E' = 40,660 cm(-1)) was prepared by 248 nm excimer laser excitation followed by rapid radiationless relaxation to the ground electronic state. Pyridine then collides with CO2, populating the high rotational CO2 states with large amounts of translational energy. The CO2 nascent rotational population distribution of the high-J (J = 58-80) tail of the 00(0)0 state was probed at short times following the excimer laser pulse to measure rate constants and probabilities for collisions populating these CO2 rotational states. Doppler spectroscopy was used to measure the CO2 recoil velocity distribution for J = 58-80 of the 00(0)0 state. The energy-transfer distribution function, P(E,E'), from E' - E approximately 1300-7000 cm(-1) was obtained by re-sorting the state-indexed energy-transfer probabilities as a function of DeltaE. P(E,E') is fit to an exponential or biexponential function to determine the average energy transferred in a single collision between pyridine and CO2. Also obtained are fit parameters that can be compared to previously studied systems (pyrazine, C6F6, methylpyrazine, and pyrimidine/CO2). Although the rotational and translational temperatures that describe pyridine/CO2 energy transfer are similar to previous systems, the energy-transfer probabilities are much smaller. P(E,E') fit parameters for pyridine/CO2 and the four previously studied systems are compared to various donor molecular properties. Finally, P(E,E') is analyzed in the context of two models, one indicating that P(E,E') shape is primarily determined by the low-frequency out-of-plane donor vibrational modes, and the other that indicates that P(E,E') shape can be determined from how the donor molecule final density of states changes with DeltaE.
Moran, M.J.; Clawges, R.M.; Zogorski, J.S.
2002-01-01
The detection frequency of methyl tert-butyl ether (MTBE) in ground and surface water of the United States is positively related to the content of MTBE in gasoline in various metropolitan areas of the U.S. The frequency of detection of MTBE is generally higher in areas that use larger amounts of MTBE in gasoline. Sampling of surface and ground water by the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program between 1993 and 1998 revealed a frequent detection of low concentrations of MTBE. In this analysis, data from several national-scale gasoline surveys are examined and data from one survey that is most extensive in geographic and temporal coverage is used to relate the detection of MTBE in ground and surface water to the volumetric content of MTBE in gasoline.