Signatures of Anderson localization excited by an optical frequency comb
Gentilini, S.
2010-01-25
We investigate Anderson localization of light as occurring in ultrashort excitations. A theory based on time dependent coupled-mode equations predicts universal features in the spectrum of the transmitted pulse. In particular, the process of strong localization of light is shown to correspond to the formation of peaks in both the amplitude and in the group delay of the transmitted pulse. Parallel ab initio simulations made with finite-difference time-domain codes and molecular dynamics confirm theoretical predictions, while showing that there exists an optimal degree of disorder for the strong localization. © 2010 The American Physical Society.
Anderson localization in metallic nanoparticle arrays
Mai, Zhijie; Lin, Fang; Pang, Wei; Xu, Haitao; Tan, Suiyan; Fu, Shenhe; Li, Yongyao
2016-06-01
Anderson localization has been observed in various types of waves, such as matter waves, optical waves and acoustic waves. Here we reveal that the effect of Anderson localization can be also induced in metallic nonlinear nanoparticle arrays excited by a random electrically driving field. We find that the dipole-induced nonlinearity results in ballistic expansion of dipole intensity during evolution; while the randomness of the external driving field can suppress such an expansion. Increasing the strength of randomness above the threshold value, a localized pattern of dipole intensity can be generated in the metallic nanoparticle arrays. By means of statistics, the mean intensity distribution of the dipoles reveals the formation of Anderson localization. We further show that the generated Anderson localization is highly confined, with its size down to the scale of incident wavelength. The reported results might facilitate the manipulations of electromagnetic fields in the scale of wavelength.
Anderson localization in metallic nanoparticle arrays
Mai, Zhijie; Pang, Wei; Xu, Haitao; Tan, Suiyan; Fu, Shenhe; Li, Yongyao
2016-01-01
Anderson localization has been observed in various types of waves, such as matter waves, optical waves and acoustic waves. Here we reveal that the effect of Anderson localization can be also induced in metallic nonlinear nanoparticle arrays excited by a random electrically driving field. We find that the dipole-induced nonlinearity results in ballistic expansion of dipole intensity during evolution; while the randomness of the external driving field can suppress such an expansion. Increasing the strength of randomness above the threshold value, a localized pattern of dipole intensity can be generated in the metallic nanoparticle arrays. By means of statistics, the mean intensity distribution of the dipoles reveals the formation of Anderson localization. We further show that the generated Anderson localization is highly confined, with its size down to the scale of incident wavelength. The reported results might facilitate the manipulations of electromagnetic fields in the scale of wavelength.
50 Years of Anderson Localization
Abrahams, Elihu
2010-01-01
In his groundbreaking paper Absence of diffusion in certain random lattices (1958), Philip W. Anderson originated, described and developed the physical principles underlying the phenomenon of the localization of quantum objects due to disorder. Anderson's 1977 Nobel Prize citation featured that paper, which was fundamental for many subsequent developments in condensed matter theory and technical applications. After more than a half century, the subject continues to be of fundamental importance. In particular, in the last 25 years, the phenomenon of localization has proved to be crucial for the
Anderson localization from classical trajectories
Brouwer, Piet W.; Altland, Alexander
2008-01-01
We show that Anderson localization in quasi-one dimensional conductors with ballistic electron dynamics, such as an array of ballistic chaotic cavities connected via ballistic contacts, can be understood in terms of classical electron trajectories only. At large length scales, an exponential proliferation of trajectories of nearly identical classical action generates an abundance of interference terms, which eventually leads to a suppression of transport coefficients. We quantitatively descri...
Effect of coulomb interaction on Anderson localization
We study the quantum mechanics of interacting particles in a disordered system, and in particular, what happens to Anderson localisation when interaction is taken into account. In the first part, one looks at the excited states of two particles in one dimension. For this model, it has been shown (Shepelyansky 1994) that a local repulsive interaction can partially destroy Anderson localisation. Here, we show that this model has similarities with the three-dimensional Anderson model at the metal-insulator transition. In particular, the maximum of rigidity obtained in the spectral statistics correspond to some intermediary statistics that cannot be described by random matrix theory neither by a Poisson statistics. The wave functions show a multifractal behaviour and the spreading of the center of mass of a wave packet is logarithmic in time. The second part deals with the ground state of a finite density of spinless fermions in two dimensions. After the scaling theory of localisation, it was commonly accepted that there was no metal in two dimensions. This idea has been challenged by the observation of a metal-insulator transition in low density electron gas (Kravchenko et al. 1994). We propose a scenario in which a metallic phase occurs between the Anderson insulator and the pinned Wigner crystal. This intermediate phase is characterized by an alignment of the local currents flowing in the system. (author)
Anderson localization in nonlocal nonlinear media
Folli, Viola; Conti, Claudio
2012-01-01
The effect of focusing and defocusing nonlinearities on Anderson localization in highly nonlocal media is theoretically and numerically investigated. A perturbative approach is developed to solve the nonlocal nonlinear Schroedinger equation in the presence of a random potential, showing that nonlocality stabilizes Anderson states.
Probing the statistical properties of Anderson localization with quantum emitters
Smolka, Stephan; Nielsen, Henri Thyrrestrup; Sapienza, Luca;
2011-01-01
embedded in disordered photonic crystal waveguides as light sources. Anderson-localized modes are efficiently excited and the analysis of the photoluminescence spectra allows us to explore their statistical properties, for example the localization length and average loss length. With increasing the amount...
Random nanolasing in the Anderson localized regime
Liu, Jin; Garcia, P. D.; Ek, Sara;
2014-01-01
multiple scattering. The applicability of random lasers has been limited due to multidirectional emission, lack of tunability, and strong mode competition with chaotic fluctuations due to a weak mode confinement. The regime of Anderson localization of light has been proposed for obtaining stable multimode...... random lasing, and initial work concerned macroscopic one-dimensional layered media. Here, we demonstrate on-chip random nanolasers where the cavity feedback is provided by the intrinsic disorder. The strong confinement achieved by Anderson localization reduces the spatial overlap between lasing modes...
Universal mechanism for Anderson and weak localization.
Filoche, Marcel; Mayboroda, Svitlana
2012-09-11
Localization of stationary waves occurs in a large variety of vibrating systems, whether mechanical, acoustical, optical, or quantum. It is induced by the presence of an inhomogeneous medium, a complex geometry, or a quenched disorder. One of its most striking and famous manifestations is Anderson localization, responsible for instance for the metal-insulator transition in disordered alloys. Yet, despite an enormous body of related literature, a clear and unified picture of localization is still to be found, as well as the exact relationship between its many manifestations. In this paper, we demonstrate that both Anderson and weak localizations originate from the same universal mechanism, acting on any type of vibration, in any dimension, and for any domain shape. This mechanism partitions the system into weakly coupled subregions. The boundaries of these subregions correspond to the valleys of a hidden landscape that emerges from the interplay between the wave operator and the system geometry. The height of the landscape along its valleys determines the strength of the coupling between the subregions. The landscape and its impact on localization can be determined rigorously by solving one special boundary problem. This theory allows one to predict the localization properties, the confining regions, and to estimate the energy of the vibrational eigenmodes through the properties of one geometrical object. In particular, Anderson localization can be understood as a special case of weak localization in a very rough landscape. PMID:22927384
Anderson localization of light with topological dislocations
Lobanov, Valery E; Vysloukh, Victor A; Torner, Lluis
2013-01-01
We predict Anderson localization of light with nested screw topological dislocations propagating in disordered two-dimensional arrays of hollow waveguides illuminated by vortex beams. The phenomenon manifests itself in the statistical presence of topological dislocations in ensemble-averaged output distributions accompanying standard disorder-induced localization of light spots. Remarkably, screw dislocations are captured by the light spots despite the fast and irregular transverse displacements and topological charge flipping undertaken by the dislocations due to the disorder. The statistical averaged modulus of the output local topological charge depends on the initial vorticity carried by the beam.
Distribution of critical temperature at Anderson localization
Gammag, Rayda; Kim, Ki-Seok
2016-05-01
Based on a local mean-field theory approach at Anderson localization, we find a distribution function of critical temperature from that of disorder. An essential point of this local mean-field theory approach is that the information of the wave-function multifractality is introduced. The distribution function of the Kondo temperature (TK) shows a power-law tail in the limit of TK→0 regardless of the Kondo coupling constant. We also find that the distribution function of the ferromagnetic transition temperature (Tc) gives a power-law behavior in the limit of Tc→0 when an interaction parameter for ferromagnetic instability lies below a critical value. However, the Tc distribution function stops the power-law increasing behavior in the Tc→0 limit and vanishes beyond the critical interaction parameter inside the ferromagnetic phase. These results imply that the typical Kondo temperature given by a geometric average always vanishes due to finite density of the distribution function in the TK→0 limit while the typical ferromagnetic transition temperature shows a phase transition at the critical interaction parameter. We propose that the typical transition temperature serves a criterion for quantum Griffiths phenomena vs smeared transitions: Quantum Griffiths phenomena occur above the typical value of the critical temperature while smeared phase transitions result at low temperatures below the typical transition temperature. We speculate that the ferromagnetic transition at Anderson localization shows the evolution from quantum Griffiths phenomena to smeared transitions around the critical interaction parameter at low temperatures.
Kolmogorov turbulence, Anderson localization and KAM integrability
Shepelyansky, D. L.
2012-06-01
The conditions for emergence of Kolmogorov turbulence, and related weak wave turbulence, in finite size systems are analyzed by analytical methods and numerical simulations of simple models. The analogy between Kolmogorov energy flow from large to small spacial scales and conductivity in disordered solid state systems is proposed. It is argued that the Anderson localization can stop such an energy flow. The effects of nonlinear wave interactions on such a localization are analyzed. The results obtained for finite size system models show the existence of an effective chaos border between the Kolmogorov-Arnold-Moser (KAM) integrability at weak nonlinearity, when energy does not flow to small scales, and developed chaos regime emerging above this border with the Kolmogorov turbulent energy flow from large to small scales.
Anderson localization and momentum-space entanglement
We consider Anderson localization and the associated metal–insulator transition for non-interacting fermions in D = 1, 2 space dimensions in the presence of spatially correlated on-site random potentials. To assess the nature of the wave function, we follow a recent proposal to study momentum-space entanglement. For a D = 1 model with long-range disorder correlations, both the entanglement spectrum and the entanglement entropy allow us to clearly distinguish between extended and localized states based upon a single realization of disorder. However, for other models, including the D = 2 case with long-range correlated disorder, we find that the method is not similarly successful. We analyze the reasons for its failure, concluding that the much desired generalization to higher dimensions may be problematic. (paper)
Controlling Anderson localization in disordered photonic crystal waveguides
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren;
2010-01-01
In most experiments on Anderson localization so far, only completely random systems without any long-range correlation between the scattering sites have been used, meaning that the Anderson localized modes cannot be controlled. Strongly confined modes were recently observed in the slow-light regime...... of a disordered photonic crystal waveguide and attributed to Anderson localization. We have tested this hypothesis by measuring the light localization length, ξloc, in a disordered photonic crystal waveguide and checked explicitly the criterion of one dimensional Anderson localization that ξloc is...... shorter than the waveguide length LS. Our measurements demonstrate for the first time the close relation between light localization and density of states, which can be used ultimately for controlling Anderson localized modes....
Controlling Anderson localization in disordered photonic crystal waveguides
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren; Lodahl, Peter
2010-01-01
In most experiments on Anderson localization so far, only completely random systems without any long-range correlation between the scattering sites have been used, meaning that the Anderson localized modes cannot be controlled. Strongly confined modes were recently observed in the slow-light regime...
Controlling Anderson localization in disordered photonic crystal waveguides
Smolka, Stephan; Garcia, Pedro D.; Lodahl, Peter
2010-01-01
We prove Anderson localization in the slow-light regime of a photonic crystal waveguide by measuring the ensemble-averaged localization length which is controlled by the dispersion of the disordered photonic crystal waveguide.......We prove Anderson localization in the slow-light regime of a photonic crystal waveguide by measuring the ensemble-averaged localization length which is controlled by the dispersion of the disordered photonic crystal waveguide....
Transverse Anderson localization of light: a tutorial review
Mafi, Arash
2015-01-01
This tutorial review gives an overview of the transverse Anderson localization of light in one and two transverse dimensions. A pedagogical approach is followed throughout the presentation, where many aspects of localization are illustrated by means of a few simple models. The tutorial starts with some basic aspects of random matrix theory, and light propagation through and reflection from a random stack of dielectric slabs. Transverse Anderson localization of light in one- and two-dimensiona...
Controlling Anderson localization in disordered photonic crystal waveguides
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren;
structures [1,2]. Originally proposed for electrons by P. W. Anderson [3], only completely random systems without any long-range correlation between the scattering sites have been used so far, meaning that the Anderson-localized modes cannot be controlled. In disordered photonic crystals, these modes are...... predicted to appear at frequencies in or near a band gap [4] providing a possible way to control Anderson-localized modes. We have tested this hypothesis by measuring the light localization length, ξ, in a disordered photonic crystal waveguide (PCW) as a function of the dispersive slowdown factor of light...... of the waveguide. Our measurements demonstrate for the first time the close relation between light localization and density of states [5], which can be used ultimately for controlling the extension and spectral position of Anderson-localized modes....
Cavity quantum electrodynamics in the Anderson-localized regime
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2010-01-01
We experimentally measure, by means of time-resolved photoluminescence spectroscopy, a 15-fold enhancement of the spontaneous emission decay rate of single semiconductor quantum dots coupled to disorder-induced Anderson-localized modes with efficiencies reaching 94%....
Anderson localization of spinons in a spin-1/2 antiferromagnetic Heisenberg chain
Pan, B. Y.; Zhou, S. Y.; Hong, X. C.; Qiu, X; Li, S. Y.
2012-01-01
Anderson localization is a general phenomenon of wave physics, which stems from the interference between multiple scattering paths1,2. It was originally proposed for electrons in a crystal, but later was also observed for light3-5, microwaves6, ultrasound7,8, and ultracold atoms9-12. Actually, in a crystal, besides electrons there may exist other quasiparticles such as magnons and spinons. However the search for Anderson localization of these magnetic excitations is rare so far. Here we repor...
Multiple-beam Propagation in an Anderson Localized Optical Fiber
Karbasi, Salman; Mafi, Arash
2012-01-01
We investigate the simultaneous propagation of multiple beams in a disordered Anderson localized optical fiber. The profiles of each beam fall off exponentially, enabling multiple channels at high-density. We examine the influence of fiber bends on the movement of the beam positions, which we refer to as drift. We investigate the extent of the drift of localized beams induced by macro-bending and show that it is possible to design Anderson localized optical fibers which can be used for practical beam-multiplexing applications.
Absence of Anderson localization in certain random lattices
Choi, Wonjun; Yin, Cheng; Hooper, Ian R.; Bernes, William L.; Bertolotti, Jacopo
2016-01-01
We report on the transition between an Anderson localized regime and a conductive regime in a 1D scattering system with correlated disorder. We show experimentally that when long-range correlations, in the form of a power-law spectral density with power larger than 2, are introduced the localization length becomes much bigger than the sample size and the transmission peaks typical of an Anderson localized system merge into a pass band. As other forms of long-range correlations are known to ha...
Interplay of Anderson localization and strong interaction in disordered systems
We study the interplay of disorder localization and strong local interactions within the Anderson-Hubbard model. Taking into account local Mott-Hubbard physics and static screening of the disorder potential, the system is mapped onto an effective single-particle Anderson model, which is studied within the self-consistent theory of electron localization. For fermions, we find rich nonmonotonic behavior of the localization length ξ, particularly in two-dimensional systems, including an interaction-induced exponential enhancement of ξ for small and intermediate disorders and a strong reduction of ξ due to hopping suppression by strong interactions. In three dimensions, we identify for half filling a Mott-Hubbard-assisted Anderson localized phase existing between the metallic and the Mott-Hubbard-gapped phases. For small U there is re-entrant behavior from the Anderson localized phase to the metallic phase. For bosons, the unrestricted particle occupation number per lattice site yields a monotonic enhancement of ξ as a function of decreasing interaction, which we assume to persist until the superfluid Bose-Einstein condensate phase is entered. Besides, we study cold atomic gases expanding, by a diffusion process, in a weak random potential. We show that the density-density correlation function of the expanding gas is strongly affected by disorder and we estimate the typical size of a speckle spot, i.e., a region of enhanced or depleted density. Both a Fermi gas and a Bose-Einstein condensate (in a mean-field approach) are considered. (orig.)
Interplay of Anderson localization and strong interaction in disordered systems
Henseler, Peter
2010-01-15
We study the interplay of disorder localization and strong local interactions within the Anderson-Hubbard model. Taking into account local Mott-Hubbard physics and static screening of the disorder potential, the system is mapped onto an effective single-particle Anderson model, which is studied within the self-consistent theory of electron localization. For fermions, we find rich nonmonotonic behavior of the localization length {xi}, particularly in two-dimensional systems, including an interaction-induced exponential enhancement of {xi} for small and intermediate disorders and a strong reduction of {xi} due to hopping suppression by strong interactions. In three dimensions, we identify for half filling a Mott-Hubbard-assisted Anderson localized phase existing between the metallic and the Mott-Hubbard-gapped phases. For small U there is re-entrant behavior from the Anderson localized phase to the metallic phase. For bosons, the unrestricted particle occupation number per lattice site yields a monotonic enhancement of {xi} as a function of decreasing interaction, which we assume to persist until the superfluid Bose-Einstein condensate phase is entered. Besides, we study cold atomic gases expanding, by a diffusion process, in a weak random potential. We show that the density-density correlation function of the expanding gas is strongly affected by disorder and we estimate the typical size of a speckle spot, i.e., a region of enhanced or depleted density. Both a Fermi gas and a Bose-Einstein condensate (in a mean-field approach) are considered. (orig.)
A modal perspective on the transverse Anderson localization of light in disordered optical lattices
Karbasi, Salman; Mafi, Arash
2013-01-01
We frame the transverse Anderson localization of light in a one-dimensional disordered optical lattice in the language of localized propagating eigenmodes. The modal analysis allows us to explore localization behavior of a disordered lattice independent of the properties of the external excitation. Various localization-related phenomena, such as the periodic revival of a propagating Anderson-localized beam are easily explained in modal language. We characterize the localization strength by the average width of the guided modes and carry out a detailed analysis of localization behavior as a function of the optical and geometrical parameters of the disordered lattice. We also show that in order to obtain a minimum average mode width, the average width of the individual random sites in the disordered lattice must be larger than the wavelength of the light by approximately a factor of two or more, and the optimum site width for the maximum localization depends on the design parameters of the disordered lattice.
Controlling Anderson localization in disordered photonic crystal waveguides
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren; Lodahl, Peter
Quantum optics and quantum information technologies require enhancement of light-matter interaction by, for example, confining light in a small volume. A very recently demonstrated route towards light confinement makes use of multiple scattering of light and wave interference in disordered photonic...... structures [1,2]. Originally proposed for electrons by P. W. Anderson [3], only completely random systems without any long-range correlation between the scattering sites have been used so far, meaning that the Anderson-localized modes cannot be controlled. In disordered photonic crystals, these modes are...
Cavity quantum electrodynamics with Anderson-localized modes
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren;
2010-01-01
factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices....
Transverse Anderson localization of light: a tutorial review
Mafi, Arash
2015-01-01
This tutorial review gives an overview of the transverse Anderson localization of light in one and two transverse dimensions. A pedagogical approach is followed throughout the presentation, where many aspects of localization are illustrated by means of a few simple models. The tutorial starts with some basic aspects of random matrix theory, and light propagation through and reflection from a random stack of dielectric slabs. Transverse Anderson localization of light in one- and two-dimensional coupled waveguide arrays is subsequently established and discussed. Recent experimental observations of localization and image transport in disordered optical fibers are discussed. More advanced topics, such as hyper-transport in longitudinally varying disordered waveguides, the impact of nonlinearity, and propagation of partially coherent and quantum light, are also examined.
Absence of Anderson localization in certain random lattices
Choi, Wonjun; Hooper, Ian R; Bernes, William L; Bertolotti, Jacopo
2016-01-01
We report on the transition between an Anderson localized regime and a conductive regime in a 1D scattering system with correlated disorder. We show experimentally that when long-range correlations, in the form of a power-law spectral density with power larger than 2, are introduced the localization length becomes much bigger than the sample size and the transmission peaks typical of an Anderson localized system merge into a pass band. As other forms of long-range correlations are known to have the opposite effect, i.e. to enhance localization, our results show that care is needed when discussing the effects of correlations, as different kinds of long-range correlations can give rise to very different behavior.
Photon transport enhanced by transverse Anderson localization in disordered superlattices
Hsieh, Pin-Chun; McMillan, James; Tsai, Min-An; Lu, Ming; Panoiu, Nicolae; Wong, Chee Wei
2014-01-01
One of the daunting challenges in optical physics is to accurately control the flow of light at the subwavelength scale, by patterning the optical medium one can design anisotropic media. The light transport can also be significantly affected by Anderson localization, namely the wave localization in a disordered medium, a ubiquitous phenomenon in wave physics. Here we report the photon transport and collimation enhanced by transverse Anderson localization in chip-scale dispersion engineered anisotropic media. We demonstrate a new type of anisotropic photonic structure in which diffraction is nearly completely arrested by cascaded resonant tunneling through transverse guided resonances. By perturbing the shape of more than 4,000 scatterers in these superlattices we add structural disordered in a controlled manner and uncover the mechanism of disorder-induced transverse localization at the chip-scale. Arrested spatial divergence is captured in the power-law scaling, along with exponential asymmetric mode profil...
Many-body Anderson localization in one-dimensional systems
Delande, Dominique; Sacha, Krzysztof; Płodzień, Marcin; Avazbaev, Sanat K.; Zakrzewski, Jakub
2013-04-01
We show, using quasi-exact numerical simulations, that Anderson localization in a disordered one-dimensional potential survives in the presence of attractive interaction between particles. The localization length of the particles' center of mass—computed analytically for weak disorder—is in good agreement with the quasi-exact numerical observations using the time evolving block decimation algorithm. Our approach allows for simulation of the entire experiment including the final measurement of all atom positions.
Brambila, Danilo
2012-01-01
We have theoretically studied Anderson localization in a 2D+1 nonlinear kicked rotor model. The system shows a very rich dynamical behavior, where the Anderson localization is suppressed and soliton wave-particles undergo a superdiffusive motion.
Multi-Scale Jacobi Method for Anderson Localization
Imbrie, John Z.
2015-11-01
A new KAM-style proof of Anderson localization is obtained. A sequence of local rotations is defined, such that off-diagonal matrix elements of the Hamiltonian are driven rapidly to zero. This leads to the first proof via multi-scale analysis of exponential decay of the eigenfunction correlator (this implies strong dynamical localization). The method has been used in recent work on many-body localization (Imbrie in On many-body localization for quantum spin chains, arXiv:1403.7837 URL"/> , 2014).
Experimental observation of Anderson localization in laser-kicked molecular rotors
Bitter, Martin
2016-01-01
We observe and study the phenomenon of Anderson localization in a system of true quantum kicked rotors. Nitrogen molecules in a supersonic molecular jet are cooled down to 27~K and are rotationally excited by a periodic train of 24~high-intensity femtosecond pulses. Exponential distribution of the molecular angular momentum - the most unambiguous signature of Anderson localization - is measured directly by means of coherent Raman scattering. We demonstrate the suppressed growth of the molecular rotational energy with the number of laser kicks and study the dependence of the localization length on the kick strength. Both timing and amplitude noise in the pulse train is shown to destroy the localization and revive the diffusive growth of angular momentum.
Quasiperiodic driving of Anderson localized waves in one dimension
Hatami, H.; Danieli, C.; Bodyfelt, J. D.; Flach, S
2016-01-01
We consider a quantum particle in a one-dimensional disordered lattice with Anderson localization, in the presence of multi-frequency perturbations of the onsite energies. Using the Floquet representation, we transform the eigenvalue problem into a Wannier-Stark basis. Each frequency component contributes either to a single channel or a multi-channel connectivity along the lattice, depending on the control parameters. The single channel regime is essentially equivalent to the undriven case. T...
Quasiperiodic driving of Anderson localized waves in one dimension
Hatami, H.; Danieli, C.; Bodyfelt, J. D.; Flach, S.
2016-06-01
We consider a quantum particle in a one-dimensional disordered lattice with Anderson localization in the presence of multifrequency perturbations of the onsite energies. Using the Floquet representation, we transform the eigenvalue problem into a Wannier-Stark basis. Each frequency component contributes either to a single channel or a multichannel connectivity along the lattice, depending on the control parameters. The single-channel regime is essentially equivalent to the undriven case. The multichannel driving increases substantially the localization length for slow driving, showing two different scaling regimes of weak and strong driving, yet the localization length stays finite for a finite number of frequency components.
Integrals of motion for one-dimensional Anderson localized systems
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; Shastry, B. Sriram
2016-03-01
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. We answer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precise sense, motivate our construction. We note that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order. We show that despite the infinite range hopping, all states but one are localized. We also study the conservation laws for the disorder free Aubry-Andre model, where the states are either localized or extended, depending on the strength of a coupling constant. We formulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry-Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Finally, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.
Defect-controlled Anderson localization of light in photonic lattices
The transverse localization of light in a disordered photonic lattice with a central defect is analyzed numerically. The effect of different input beam widths on various regimes of Anderson localization is investigated. The inclusion of a defect enhances the localization of both narrow and broad beams, as compared to the lattice with no defect. But, in the case of a broad beam a higher disorder level is needed to reach the same localization as for a narrow input beam. It is also investigated how the transverse localization of light in such geometries depends on both the strength of disorder and the strength of nonlinearity in the system. While in the linear regime the localization is most pronounced in the lattice with the defect, in the nonlinear regime this is not the case. (paper)
Waintal, X
1999-09-10
We study the quantum mechanics of interacting particles in a disordered system, and in particular, what happens to Anderson localisation when interaction is taken into account. In the first part,one looks at the excited states of two particles in one dimension. For this model, it has been shown (Shepelyansky 1994) that a local repulsive interaction can partially destroy Anderson localisation. Here, we show that this model has similarities with the three-dimensional Anderson model at the metal-insulator transition. In particular, the maximum of rigidity obtained in the spectral statistics correspond to some intermediary statistics that cannot be described by random matrix theory neither by a Poisson statistics. The wave functions show a multifractal behaviour and the spreading of the center of mass of a wave packet is logarithmic in time. The second part deals with the ground state of a finite density of spinless fermions in two dimensions. After the scaling theory of localisation, it was commonly accepted that there was no metal in two dimensions. This idea has been challenged by the observation of a metal-insulator transition in low density electron gas (Kravchenko et al. 1994). We propose a scenario in which a metallic phase occurs between the Anderson insulator and the pinned Wigner crystal. This intermediate phase is characterized by an alignment of the local currents flowing in the system. (author)
Transversal Anderson localization of sound in acoustic waveguide arrays
We present designs of one-dimensional acoustic waveguide arrays and investigate wave propagation inside. Under the condition of single identical waveguide mode and weak coupling, the acoustic wave motion in waveguide arrays can be modeled with a discrete mode-coupling theory. The coupling constants can be retrieved from simulations or experiments as the function of neighboring waveguide separations. Sound injected into periodic arrays gives rise to the discrete diffraction, exhibiting ballistic or extended transport in transversal direction. But sound injected into randomized waveguide arrays readily leads to Anderson localization transversally. The experimental results show good agreement with simulations and theoretical predictions. (paper)
Experimental Observation of Two-Dimensional Anderson Localization with the Atomic Kicked Rotor
Manai, Isam; Clément, Jean-François; Chicireanu, Radu; Hainaut, Clément; Garreau, Jean Claude; Szriftgiser, Pascal; Delande, Dominique
2015-01-01
Dimension 2 is expected to be the lower critical dimension for Anderson localization in a time-reversal-invariant disordered quantum system: the dynamics is generically localized in dimension lower than 2, while it presents a transition from a diffusive regime at weak disorder to a localized regime at strong disorder in dimension larger than 2. We use an atomic quasiperiodically kicked rotor – equivalent to a two-dimensional Anderson-like model – to experimentally study Anderson localization ...
Anderson localization in metamaterials and other complex media
Gredeskul, Sergey A; Asatrian, Ara A; Bliokh, Konstantin Y; Bliokh, Yuri P; Freilikher, Valentin D; Shadrivov, Ilya V
2012-01-01
We review some recent (mostly ours) results on the Anderson localization of light and electron waves in complex disordered systems, including: (i) left-handed metamaterials, (ii) magneto-active optical structures, (iii) graphene superlattices, and (iv) nonlinear dielectric media. First, we demonstrate that left-handed metamaterials can significantly suppress localization of light and lead to an anomalously enhanced transmission. This suppression is essential at the long-wavelength limit in the case of normal incidence, at specific angles of oblique incidence (Brewster anomaly), and in the vicinity of the zero-epsilon or zero-mu frequencies for dispersive metamaterials. Remarkably, in disordered samples comprised of alternating normal and left-handed metamaterials, the reciprocal Lyapunov exponent and reciprocal transmittance increment can differ from each other. Second, we study magneto-active multilayered structures, which exhibit nonreciprocal localization of light depending on the direction of propagation ...
Experimental Observation of Two-Dimensional Anderson Localization with the Atomic Kicked Rotor.
Manai, Isam; Clément, Jean-François; Chicireanu, Radu; Hainaut, Clément; Garreau, Jean Claude; Szriftgiser, Pascal; Delande, Dominique
2015-12-11
Dimension 2 is expected to be the lower critical dimension for Anderson localization in a time-reversal-invariant disordered quantum system. Using an atomic quasiperiodic kicked rotor-equivalent to a two-dimensional Anderson-like model-we experimentally study Anderson localization in dimension 2 and we observe localized wave function dynamics. We also show that the localization length depends exponentially on the disorder strength and anisotropy and is in quantitative agreement with the predictions of the self-consistent theory for the 2D Anderson localization. PMID:26705619
Density of states controls Anderson localization in disordered photonic crystal waveguides
Garcia-Fernández, David; Smolka, Stephan; Stobbe, Søren;
2010-01-01
We prove Anderson localization in a disordered photonic crystal waveguide by measuring the ensemble-averaged extinction mean-free path, ℓe, which is controlled by the dispersion in the photon density of states (DOS) of the photonic crystal waveguide. Except for the very low DOS case, where out...... demonstrates the close relation between Anderson localization and the DOS in disordered photonic crystals, which opens a promising route to controlling and exploiting Anderson-localized modes for efficient light confinement....
Averbukh I. Sh.
2013-03-01
Full Text Available We show that molecules kicked periodically by laser pulses currently used in molecular alignment experiments allow to observe effects of the periodically kicked quantum rotor in a real rotational system. Among these effects are Anderson localisation in angular momentum and the scaling of the quantum resonance. Based on this, we propose a new scheme for selective molecular rotational excitation.
Natale, Joseph; Hentschel, George
Firing-rate networks offer a coarse model of signal propagation in the brain. Here we analyze sparse, 2D planar firing-rate networks with no synapses beyond a certain cutoff distance. Additionally, we impose Dale's Principle to ensure that each neuron makes only or inhibitory outgoing connections. Using spectral methods, we find that the number of neurons participating in excitations of the network becomes insignificant whenever the connectivity cutoff is tuned to a value near or below the average interneuron separation. Further, neural activations exceeding a certain threshold stay confined to a small region of space. This behavior is an instance of Anderson localization, a disorder-induced phase transition by which an information channel is rendered unable to transmit signals. We discuss several potential implications of localization for both local and long-range computation in the brain. This work was supported in part by Grants JSMF/ 220020321 and NSF/IOS/1208126.
All-solid-state cavity QED using Anderson-localized modes in disordered photonic crystal waveguides
Lodahl, Peter; Sapienza, Luca; Nielsen, Henri Thyrrestrup;
2010-01-01
We employ Anderson-localized modes in deliberately disordered photonic crystal waveguides to confine light and enhance the interaction with matter. A 15-fold enhancement of the decay rate of a single quantum dot is observed meaning that 94% of the emitted single photons are coupled to an Anderson...
Two-photon Anderson localization in a disordered quadratic waveguide array
We theoretically investigate two-photon Anderson localization in a χ (2) waveguide array with off-diagonal disorder. The nonlinear parametric down-conversion process would enhance both the single-photon and the two-photon Anderson localization. In the strong disorder regime, the two-photon position correlation exhibits a bunching distribution around the pumped waveguides, which is independent of pumping conditions and geometrical structures of waveguide arrays. Quadratic nonlinearity can be supplied as a new ingredient for Anderson localization. Also, our results pave the way for engineering quantum states through nonlinear quantum walks. (paper)
Schulte, T.; Drenkelforth, S.; Kruse, J.; Ertmer, W.; Arlt, J.; Sacha, K.; Zakrzewski, J.; Lewenstein, M.
2005-10-01
We investigate, both experimentally and theoretically, possible routes towards Anderson-like localization of Bose-Einstein condensates in disordered potentials. The dependence of this quantum interference effect on the nonlinear interactions and the shape of the disorder potential is investigated. Experiments with an optical lattice and a superimposed disordered potential reveal the lack of Anderson localization. A theoretical analysis shows that this absence is due to the large length scale of the disorder potential as well as its screening by the nonlinear interactions. Further analysis shows that incommensurable superlattices should allow for the observation of the crossover from the nonlinear screening regime to the Anderson localized case within realistic experimental parameters.
We investigate, both experimentally and theoretically, possible routes towards Anderson-like localization of Bose-Einstein condensates in disordered potentials. The dependence of this quantum interference effect on the nonlinear interactions and the shape of the disorder potential is investigated. Experiments with an optical lattice and a superimposed disordered potential reveal the lack of Anderson localization. A theoretical analysis shows that this absence is due to the large length scale of the disorder potential as well as its screening by the nonlinear interactions. Further analysis shows that incommensurable superlattices should allow for the observation of the crossover from the nonlinear screening regime to the Anderson localized case within realistic experimental parameters
Floß, Johannes
2011-01-01
We demonstrate that the current laser technology used for field-free molecular alignment via a cascade of Raman rotational transitions allows for observing long-discussed non-linear quantum phenomena in the dynamics of the periodically kicked rotor. This includes the scaling of the absorbed energy near the conditions of quantum resonance and Anderson-like localization in the angular momentum. Based on these findings, we suggest a novel approach to tunable selective rotational excitation and alignment in a molecular mixture, using trains of short laser pulses. We demonstrate the efficiency of this approach by applying it to a mixture of two nitrogen isotopologues (14N2 and 15N2), and show that strong selectivity is possible even at room temperature.
Localization of optical excitations on random surfaces: SNOM studies
Bozhevolnyi, Sergey I.
1999-01-01
Localization of optical excitations on nanostructured metal surfaces and fractal colloid silver aggregates are studied by using a scanning near-field optical microscope (SNOM). The SNOM images obtained in both configurations exhibit spatially localized (within 150 to 250 nm) light intensity enhan...... enhancement by up to two orders of magnitude. The observed phenomena are related to strong (Anderson) localization of quasi-two-dimensional light waves....
Non-compact local excitations in spin glasses
Lamarcq, J.; Bouchaud, J.-P.; Martin, O. C.; Mezard, M.
2001-01-01
We study numerically the local low-energy excitations in the 3-d Edwards-Anderson model for spin glasses. Given the ground state, we determine the lowest-lying connected cluster of flipped spins with a fixed volume containing one given spin. These excitations are not compact, having a fractal dimension close to two, suggesting an analogy with lattice animals. Also, their energy does not grow with their size; the associated exponent is slightly negative whereas the one for compact clusters is ...
Localized Excitations from Localized Unitary Operators
Sivaramakrishnan, Allic
2016-01-01
Localized unitary operators are basic probes of locality and causality in quantum systems: localized unitary operators create localized excitations in entangled states. Working with an explicit form, we explore the properties of these operators in quantum mechanics and quantum field theory. We show that, unlike unitary operators, local non-unitary operators generically create non-local excitations. We present a local picture for quantum systems in which localized experimentalists can only act through localized Hamiltonian deformations, and therefore localized unitary operators. We demonstrate that localized unitary operators model certain quantum quenches exactly. We show how the Reeh-Schlieder theorem follows intuitively from basic properties of entanglement, non-unitary operators, and the local picture. We show that a recent quasi-particle picture for excited-state entanglement entropy in conformal field theories is not universal for all local operators. We prove a causality relation for entanglement entrop...
Image transport through a disordered optical fiber mediated by transverse Anderson localization
Karbasi, Salman; Koch, Karl W; Hawkins, Thomas; Ballato, John; Mafi, Arash
2013-01-01
Transverse Anderson localization of light allows localized optical-beam-transport through a transversely-disordered and longitudinally-invariant medium. Its successful implementation in disordered optical fibers recently resulted in the simultaneous propagation of multiple beams in a single strand of an optical fiber, suggesting potential applications for spatial beam multiplexing and image transport. We present what is, to the best of our knowledge, the first demonstration of optical image transport using transverse Anderson localization of light. The image transport quality obtained in the polymer disordered optical fiber is comparable with or better than some of the best commercially available multicore imaging fibers with less pixelation and higher contrast. A proof-of-concept glass version is also evaluated and further optimization is discussed. Our results open the way to device-level implementation of the transverse Anderson localization of light with potential applications in biological and medical im...
Transverse Anderson localization of light near Dirac points of photonic nanostructures
Deng, Hanying; Malomed, Boris A; Panoiu, Nicolae C; Ye, Fangwei
2015-01-01
We perform a comparative study of the Anderson localization of light beams in disordered layered photonic nanostructures that, in the limit of periodic layer distribution, possess either a Dirac point or a Bragg gap in the spectrum of the wavevectors. In particular, we demonstrate that the localization length of the Anderson modes increases when the width of the Bragg gap decreases, such that in the vanishingly small bandgap limit, namely when a Dirac point is formed, even extremely high levels of disorders are unable to localize the optical modes located near the Dirac point. A comparative analysis of the key features of the propagation of Anderson modes formed in the Bragg gap or near the Dirac point is also presented. Our findings could provide valuable guidelines in assessing the influence of structural disorder on the functionality of a broad array of optical nanodevices.
Observation of migrating transverse Anderson localizations of light in nonlocal media
Leonetti, Marco; Mafi, Arash; Conti, Claudio
2014-01-01
We report the experimental observation of the interaction and attraction of many localized modes in a two dimensional (2D) system realized by a disordered optical fiber supporting transverse Anderson localization. We show that a nonlocal optically nonlinear response of thermal origin alters the localization length by an amount determined by the optical power and also induces an action at a distance between the localized modes and their spatial migration. Evidence of a collective and strongly interacting regime is given.
Spectral statistics for the discrete Anderson model in the localized regime
Germinet, François
2010-01-01
We report on recent results on the spectral statistics of the discrete Anderson model in the localized phase. Our results show, in particular, that, for the discrete Anderson Hamiltonian with smoothly distributed random potential at sufficiently large coupling, the limit of the level spacing distribution is that of i.i.d. random variables distributed according to the density of states of the random Hamiltonian. This text is a contribution to the proceedings of the conference "Spectra of Random Operators and Related Topics" held at Kyoto University, 02-04/12/09 organized by N. Minami and N. Ueki.
Single-ion-pair fluorescence ratios in ruby and Anderson localization
Chu, S.; Gibbs, H. M.; Passner, A.
1981-12-01
The experiment of Koo, Walker, and Geschwind (KWG) presenting evidence for a mobility edge separating localized and extended states has been repeated and extended. Although some of the features reported by KWG were seen, there are notable qualitative and quantitative differences in our work. We conclude that there is no compelling evidence for an Anderson transition in ruby.
Anderson localization through Polyakov loops: lattice evidence and Random matrix model
Bruckmann, Falk; Kovács, Tamás G.; Schierenberg, Sebastian
2011-01-01
We investigate low-lying fermion modes in SU(2) gauge theory at temperatures above the phase transition. Both staggered and overlap spectra reveal transitions from chaotic (random matrix) to integrable (Poissonian) behavior accompanied by an increasing localization of the eigenmodes. We show that the latter are trapped by local Polyakov loop fluctuations. Islands of such "wrong" Polyakov loops can therefore be viewed as defects leading to Anderson localization in gauge theories. We find stron...
We calculated numerically the localization length of one-dimensional Anderson model with diagonal disorder. For weak disorder, we showed that the localization length changes continuously as the energy changes from the band center to the boundary of the anomalous region near the band edge. We found that all the localization lengths for different disorder strengths and different energies collapse onto a single curve, which can be fitted by a simple equation. Thus the description of the perturbation theory and the band center anomaly were unified into this equation. -- Highlights: → We study the band center anomaly of one-dimensional Anderson localization. → We study numerically the Lyapunov exponent through a parametrization method of the transfer matrix. → We give a unified equation to describe the band center anomaly and perturbation theory.
Scaling analysis of transverse Anderson localization in a disordered optical waveguide
Abaie, Behnam
2016-01-01
The intention of this manuscript is twofold. First, the mode-width probability density function (PDF) is introduced as a powerful statistical tool to study and compare the transverse Anderson localization properties of a disordered one dimensional optical waveguide. Second, by analyzing the scaling properties of the mode-width PDF with the transverse size of the waveguide, it is shown that the mode-width PDF gradually converges to a terminal configuration. Therefore, it may not be necessary to study a real-sized disordered structure in order to obtain its statistical localization properties and the same PDF can be obtained for a substantially smaller structure. This observation is important because it can reduce the often demanding computational effort that is required to study the statistical properties of Anderson localization in disordered waveguides. Using the mode-width PDF, substantial information about the impact of the waveguide parameters on its localization properties is extracted. This information ...
Non-compact local excitations in spin-glasses
Lamarcq, J.; Bouchaud, J.-P.; Martin, O. C.; Mézard, M.
2002-05-01
We study numerically the local low-energy excitations in the 3d Edwards-Anderson model for spin-glasses. Given the ground state, we determine the lowest-lying connected cluster of flipped spins with a fixed volume containing one given spin. These excitations are not compact, having a fractal dimension close to two, suggesting an analogy with lattice animals. Also, their energy does not grow with their size; the associated exponent is slightly negative whereas the one for compact clusters is positive. These findings call for a modification of the basic hypotheses underlying the droplet model.
Controlling Anderson localization in disordered heterostrctures with Lévy-type distribution
In this paper, we propose a disordered heterostructure in which the distribution of the refractive index of one of its constituents follows a Lévy-type distribution characterized by the exponent α. For the normal and oblique incidences, the effect of α variation on the localization length is investigated in different frequency ranges. As a result, the controllability of Anderson localization can be achieved by changing the exponent α in the disordered structure having heavy tailed distribution. (paper)
Light focusing in the Anderson Regime
Leonetti, Marco; Mafi, Arash; Conti, Claudio
2014-01-01
Anderson localization is a regime in which diffusion is inhibited and waves (also electromagnetic waves) get localized. Here we exploit adaptive optics to achieve focusing in disordered optical fibers in the Anderson regime. By wavefront shaping and optimization, we observe the generation of a propagation invariant beam, where light is trapped transversally by disorder, and show that Anderson localizations can be also excited by extended speckled beams. We demonstrate that disordered fibers allow a more efficient focusing action with respect to standard fibers in a way independent of their length, because of the propagation invariant features and cooperative action of transverse localizations.
Anderson localization through Polyakov loops: Lattice evidence and random matrix model
We investigate low-lying fermion modes in SU(2) gauge theory at temperatures above the phase transition. Both staggered and overlap spectra reveal transitions from chaotic (random matrix) to integrable (Poissonian) behavior accompanied by an increasing localization of the eigenmodes. We show that the latter are trapped by local Polyakov loop fluctuations. Islands of such ''wrong'' Polyakov loops can therefore be viewed as defects leading to Anderson localization in gauge theories. We find strong similarities in the spatial profile of these localized staggered and overlap eigenmodes. We discuss possible interpretations of this finding and present a sparse random matrix model that reproduces these features.
Anderson localization through Polyakov loops: Lattice evidence and random matrix model
Bruckmann, Falk; Kovács, Tamás G.; Schierenberg, Sebastian
2011-08-01
We investigate low-lying fermion modes in SU(2) gauge theory at temperatures above the phase transition. Both staggered and overlap spectra reveal transitions from chaotic (random matrix) to integrable (Poissonian) behavior accompanied by an increasing localization of the eigenmodes. We show that the latter are trapped by local Polyakov loop fluctuations. Islands of such “wrong” Polyakov loops can therefore be viewed as defects leading to Anderson localization in gauge theories. We find strong similarities in the spatial profile of these localized staggered and overlap eigenmodes. We discuss possible interpretations of this finding and present a sparse random matrix model that reproduces these features.
Anderson localization through Polyakov loops: lattice evidence and Random matrix model
Bruckmann, Falk; Schierenberg, Sebastian
2011-01-01
We investigate low-lying fermion modes in SU(2) gauge theory at temperatures above the phase transition. Both staggered and overlap spectra reveal transitions from chaotic (random matrix) to integrable (Poissonian) behavior accompanied by an increasing localization of the eigenmodes. We show that the latter are trapped by local Polyakov loop fluctuations. Islands of such "wrong" Polyakov loops can therefore be viewed as defects leading to Anderson localization in gauge theories. We find strong similarities in the spatial profile of these localized staggered and overlap eigenmodes. We discuss possible interpretations of this finding and present a sparse random matrix model that reproduces these features.
Transverse Anderson Localization in Disordered Glass Optical Fibers: A Review
Arash Mafi
2014-07-01
Full Text Available Disordered optical fibers show novel waveguiding properties that can be used for various device applications, such as beam-multiplexed optical communications and endoscopic image transport. The strong transverse scattering from the transversely disordered optical fibers results in transversely confined beams that can freely propagate in the longitudinal direction, similar to conventional optical fibers, with the advantage that any point in the cross section of the fiber can be used for beam transport. For beam multiplexing and imaging applications, it is highly desirable to make the localized beam radius as small as possible. This requires large refractive index differences between the materials that define the random features in the disordered fiber. Here, disordered glass-air fibers are briefly reviewed, where randomly placed airholes in a glass matrix provide the sufficiently large refractive index difference of 0.5 for strong random transverse scattering. The main future challenge for the fabrication of an optimally disordered glass-air fibers is to increase the fill-fraction of airholes to nearly 50% for maximum beam confinement.
Anderson localization of electrons in single crystals: Li (x) Fe(7)Se(8).
Ying, Tianping; Gu, Yueqiang; Chen, Xiao; Wang, Xinbo; Jin, Shifeng; Zhao, Linlin; Zhang, Wei; Chen, Xiaolong
2016-02-01
Anderson (disorder-induced) localization, proposed more than half a century ago, has inspired numerous efforts to explore the absence of wave diffusions in disordered media. However, the proposed disorder-induced metal-insulator transition (MIT), associated with the nonpropagative electron waves, has hardly been observed in three-dimensional (3D) crystalline materials, let alone single crystals. We report the observation of an MIT in centimeter-size single crystals of Li x Fe7Se8 induced by lattice disorder. Both specific heat and infrared reflectance measurements reveal the presence of considerable electronic states in the vicinity of the Fermi level when the MIT occurs, suggesting that the transition is not due to Coulomb repulsion mechanism. The 3D variable range hopping regime evidenced by electrical transport measurements at low temperatures indicates the localized nature of the electronic states on the Fermi level. Quantitative analyses of carrier concentration, carrier mobility, and simulated density of states (DOS) fully support that Li x Fe7Se8 is an Anderson insulator. On the basis of these results, we provide a unified DOS picture to explain all the experimental results, and a schematic diagram for finding other potential Anderson insulators. This material will thus serve as a rich playground for both theoretical and experimental investigations on MITs and disorder-induced phenomena. PMID:26989781
Simulation of Anderson localization in two-dimensional ultracold gases for pointlike disorder
Morong, W.; DeMarco, B.
2015-08-01
Anderson localization has been observed for a variety of media, including ultracold atomic gases with speckle disorder in one and three dimensions. However, observation of Anderson localization in a two-dimensional geometry for ultracold gases has been elusive. We show that a cause of this difficulty is the relatively high percolation threshold of a speckle potential in two dimensions, resulting in strong classical localization. We propose a realistic pointlike disorder potential that circumvents this percolation limit with localization lengths that are experimentally observable. The percolation threshold is evaluated for experimentally realistic parameters, and a regime of negligible classical trapping is identified. Localization lengths are determined via scaling theory, using both exact scattering cross sections and the Born approximation, and by direct simulation of the time-dependent Schrödinger equation. We show that the Born approximation can underestimate the localization length by four orders of magnitude at low energies, while exact cross sections and scaling theory provide an upper bound. Achievable experimental parameters for observing localization in this system are proposed.
Coalescence of Anderson-localized modes at an exceptional point in 2D random media
Bachelard, Nicolas; Arlandis, Julien; Touzani, Rachid; Sebbah, Patrick
2014-01-01
In non-hermitian systems, the particular position at which two eigenstates coalesce under a variation of a parameter in the complex plane is called an exceptional point. A non-perturbative theory is proposed which describes the evolution of modes in 2D open dielectric systems when permittivity distribution is modified. We successfully test this theory in a 2D disordered system to predict the position in the parameter space of the exceptional point between two Anderson-localized states. We observe that the accuracy of the prediction depends on the number of localized states accounted for. Such an exceptional point is experimentally accessible in practically relevant disordered photonic systems
Anderson Localization of Light in the Presence of Non-linear Effects
Bührer, Wolfgang
2012-01-01
The goal of the thesis presented here, was to further investigate the findings of Dr. Störzer in order to prove the wave nature of Anderson Localization. For this, two different approaches and setups were used.The first was a single photon counting Time-of-Flight setup, but with increased laser power and less noise in the detection part, where band pass filters were used as a crude spectrometer for analysing the spectral distribution of the photons travelling through highly turbid random medi...
Probing Anderson localization of light by weak non-linear effects
Breakdown of wave transport due to strong disorder is a universal phenomenon known as Anderson localization (AL). It occurs because of the macroscopic population of reciprocal multiple scattering paths, which in three dimensional systems happens at a critical scattering strength. Intensities on these random loops should thus be highly increased relative to those of a diffusive sample. In order to highlight localized modes of light, we exploit the optical nonlinearities of TiO2. Power dependent and spectrally resolved time of flight distribution measurements in transmission through slabs of TiO2 powders at various turbidities reveal that mostly long loops are affected by nonlinearities and that the deviations from diffusive transport observed at long times are due to these localized modes. Our data are a first step in the experimental investigation of the interplay between nonlinear effects and AL in 3D. (fast track communication)
Cossu, Guido
2016-01-01
We investigate the properties of the background gauge field configurations that act as disorder for the Anderson localization mechanism in the Dirac spectrum of QCD at high temperatures. We compute the eigenmodes of the M\\"obius domain-wall fermion operator on configurations generated for the $SU(3)$ gauge theory with two flavors of fermions, in the temperature range $[0.9,1.9]T_c$. We identify the source of localization of the eigenmodes with gauge configurations that are self-dual and support negative fluctuations of the Polyakov loop $P_L$, in the high temperature sea of $P_L\\sim 1$. The dependence of these observations on the boundary conditions of the valence operator is studied. We also investigate the spatial overlap of the left-handed and right-handed projected eigenmodes in correlation with the localization and the corresponding eigenvalue. We discuss an interpretation of the results in terms of monopole-instanton structures.
Cossu, Guido; Hashimoto, Shoji
2016-06-01
We investigate the properties of the background gauge field configurations that act as disorder for the Anderson localization mechanism in the Dirac spectrum of QCD at high temperatures. We compute the eigenmodes of the Möbius domain-wall fermion operator on configurations generated for the SU(3) gauge theory with two flavors of fermions, in the temperature range [0.9, 1.9]T c . We identify the source of localization of the eigenmodes with gauge configurations that are self-dual and support negative fluctuations of the Polyakov loop P L , in the high temperature sea of P L ˜ 1. The dependence of these observations on the boundary conditions of the valence operator is studied. We also investigate the spatial overlap of the left-handed and right-handed projected eigenmodes in correlation with the localization and the corresponding eigenvalue. We discuss an interpretation of the results in terms of monopole-instanton structures.
Investigation of Anderson localization in disordered heterostructures irradiated by a Gaussian beam
Ardakani, Abbas Ghasempour
2016-02-01
The propagation of a Gaussian beam through a one-dimensional disordered media is studied. By employing the transfer matrix method, the localization length as a function of frequency is calculated for different values of transverse coordinate r. It is demonstrated that the localization length significantly depends on r in different frequency ranges. This result is in contrast to those reported for a plane wave incident on disordered structures in which the localization length is transversely constant. For some frequency regions, the peak of localization length is red-shifted and becomes smaller with increasing the transverse coordinate. At some frequencies, the system is in the localized state for particular values of r, while at other r values the system is in the extend regime at the same frequencies. It is observed that the quality of localization at each frequency depends on r. To quantify the localization behavior of the whole Gaussian beam, a modified localization length is defined in terms of the input and output powers of the Gaussian beam where the dependence of Anderson localization on the transverse coordinate is considered. It is suggested that this modified localization length is used in experiments performed for study of wave propagation in one-dimensional random media under illumination of laser beams.
Suppression of Anderson localization in a graphene sheet applied by a random voltage pattern
We theoretically study the transport of electronic waves through a graphene sheet applied by a random voltage pattern in which the magnitudes and/or the widths of the voltages are random. When the magnitudes of the voltages exceed the electronic energy, the applied region can be considered as left-handed (LH) layers. Compared to the disordered structures with right-handed (RH) layers only, the spectra of the (average) density of states and the localization lengths in mixed random structures with RH and LH layers all show the suppression of Anderson localization, owing to the phase compensation effect of LH layers that reduces the long-range interference in the random system.
Efficient Localization Bounds in a Continuous N-Particle Anderson Model with Long-Range Interaction
Chulaevsky, Victor
2016-04-01
We establish strong dynamical and exponential spectral localization for a class of multi-particle Anderson models in a Euclidean space with an alloy-type random potential and a sub-exponentially decaying interaction of infinite range. For the first time in the mathematical literature, the uniform decay bounds on the eigenfunction correlators (EFCs) at low energies are proved, in the multi-particle continuous configuration space, in the (symmetrized) norm-distance, which is a natural distance in the multi-particle configuration space, and not in the Hausdorff distance. This results in uniform bounds on the EFCs in arbitrarily large but bounded domains in the physical configuration space, and not only in the actually infinite space, as in prior works on multi-particle localization in Euclidean spaces.
On the question of possible experimental observation of Anderson localization of the neutron
A possible experiment for observation of the Anderson localization of the neutron is discussed. It is shown that the localized state may be formed in the process of inelastic downscattering of thermal or cold neutrons in a highly disordered substance with low neutron capture and upscattering cross sections. According to the sense of localization of the particle, its probability density exponentially decays outside a certain region of localization. Localized particles have exponentially small chances of running away from a random system. Any particle outside the localized energy band has an exponentially small probability of getting inside a random system. Neutrons localized in this way may be captured or inelastically upscattered to the thermal (cold) energy range with a time constant dependent on the corresponding cross sections. The most convenient substances for realizing such experiments are strong coherent neutron scatters with low capture and upscattering cross sections at low temperatures. These are Be, BeO, C, D2, D2O and CO2. The lifetime of trapped (localized) neutrons in the sample is measured by counting the upscattered neutrons with neutron counter surrounding the sample. Estimations of experimental parameters relevant to such an experiment are given
Javadi, Alisa; Sapienza, Luca; Thyrrestrup, Henri; Lodahl, Peter
2013-01-01
Optical nanostructures have proven to be meritorious for tailoring the emission properties of quantum emitters. However, unavoidable fabrication imperfections may represent a nuisance. Quite remarkably, disorder offers new opportunities since light can be efficiently confined by random multiple scattering leading to Anderson localization. Here we investigate the effect of such disorder-induced cavities on the emission dynamics of single quantum dots embedded in disordered photonic-crystal waveguides. We present time-resolved measurements of both the total emission from Anderson-localized cavities and from single emitters that are coupled to the cavities. We observe both strongly inhibited and enhanced decay rates relative to the rate of spontaneous emission in a homogeneous medium. From a statistical analysis, we report an average Purcell factor of 2 in without any control on the quantum dot - cavity detuning. By spectrally tuning individual quantum dots into resonance with Anderson-localized modes, a maximum...
Monthus, Cécile
2016-03-01
The generalization of the Dyson Brownian motion approach of random matrices to Anderson localization (AL) models (Chalker et al 1996 Phys. Rev. Lett. 77 554) and to many-body localization (MBL) Hamiltonians (Serbyn and Moore 2015 arXiv:1508.07293) is revisited to extract the level repulsion exponent β, where β =1 in the delocalized phase governed by the Wigner-Dyson statistics, β =0 , in the localized phase governed by the Poisson statistics, and 0 {{|}2} for the same eigenstate m = n and for consecutive eigenstates m = n + 1. For the Anderson localization tight-binding Hamiltonian with random on-site energies h i , we find β =2{{Y}n,n+1}(N)/≤ft({{Y}n,n}(N)-{{Y}n,n+1}(N)\\right) in terms of the density correlation matrix {{Y}nm}(N)\\equiv {\\sum}i=1N| {{|}2}| {{|}2} for consecutive eigenstates m = n + 1, while the diagonal element m = n corresponds to the inverse participation ratio {{Y}nn}(N)\\equiv {\\sum}i=1N| {{|}4} of the eigenstate |{φn}> .
This paper proposes a one-dimensional random structure composed of three types of alternating layers of dielectric and magnetized plasma materials. By employing the transfer matrix method, the localization lengths of the waves propagating in opposite directions are calculated. The numerical results demonstrate that nonreciprocal features appear in the averaged localization length and individual transmission resonances. However, in the short wavelength regime, the nonreciprocal behavior of the averaged localization length disappears, and the maximum of differential transmission decreases. The author investigates the effects of the external magnetic field, incident angle, collision frequency, and plasma density of the plasma layer on the reciprocal properties. The frequencies at which nonreciprocity occurs depend on the external magnetic field. Thus, it is possible to realize a photonic diode that is tunable with the external magnetic field. Also found is that for small angles of incidence no significant difference exists between the localization lengths of the forward and backward waves. There is a lower limit for the plasma density of the magnetized plasma layers to obtain nonreciprocal Anderson localization. As the collision frequency increases, the nonreciprocal features of the proposed random system survive. (papers)
coexist in waveguide-like systems with randomly corrugated boundaries, specifically, the entropic localization and the one-dimensional Anderson (disorder-driven) localization. If the particular mode propagates across the rough segment ballistically, the Fabry–Pérot-type oscillations should be observed in the conductance, which are suppressed for the mode transferred in the Anderson-localized regime
Highlights: → Statistics of normalized eigenfunctions in one-dimensional Anderson localization at E = 0 is studied. → Moments of inverse participation ratio are calculated. → Equation for generating function is derived at E = 0. → An exact solution for generating function at E = 0 is obtained. → Relation of the generating function to the phase distribution function is established. - Abstract: The one-dimensional (1d) Anderson model (AM), i.e. a tight-binding chain with random uncorrelated on-site energies, has statistical anomalies at any rational point f=(2a)/(λE) , where a is the lattice constant and λE is the de Broglie wavelength. We develop a regular approach to anomalous statistics of normalized eigenfunctions ψ(r) at such commensurability points. The approach is based on an exact integral transfer-matrix equation for a generating function Φr(u, φ) (u and φ have a meaning of the squared amplitude and phase of eigenfunctions, r is the position of the observation point). This generating function can be used to compute local statistics of eigenfunctions of 1d AM at any disorder and to address the problem of higher-order anomalies at f=p/q with q > 2. The descender of the generating function Pr(φ)≡Φr(u=0,φ) is shown to be the distribution function of phase which determines the Lyapunov exponent and the local density of states. In the leading order in the small disorder we derived a second-order partial differential equation for the r-independent ('zero-mode') component Φ(u, φ) at the E = 0 (f=1/2 ) anomaly. This equation is nonseparable in variables u and φ. Yet, we show that due to a hidden symmetry, it is integrable and we construct an exact solution for Φ(u, φ) explicitly in quadratures. Using this solution we computed moments Im = N2m> (m ≥ 1) for a chain of the length N → ∞ and found an essential difference between their m-behavior in the center-of-band anomaly and for energies outside this anomaly. Outside the anomaly the
Hewson, Alex C.; Bauer, Johannes
2010-01-01
We show that information on the probability density of local fluctuations can be obtained from a numerical renormalisation group calculation of a reduced density matrix. We apply this approach to the Anderson-Holstein impurity model to calculate the ground state probability density $\\rho(x)$ for the displacement $x$ of the local oscillator. From this density we can deduce an effective local potential for the oscillator and compare its form with that obtained from a semiclassical approximation...
Pietracaprina, Francesca; Ros, Valentina; Scardicchio, Antonello
2016-02-01
In this paper we analyze the predictions of the forward approximation in some models which exhibit an Anderson (single-body) or many-body localized phase. This approximation, which consists of summing over the amplitudes of only the shortest paths in the locator expansion, is known to overestimate the critical value of the disorder which determines the onset of the localized phase. Nevertheless, the results provided by the approximation become more and more accurate as the local coordination (dimensionality) of the graph, defined by the hopping matrix, is made larger. In this sense, the forward approximation can be regarded as a mean-field theory for the Anderson transition in infinite dimensions. The sum can be efficiently computed using transfer matrix techniques, and the results are compared with the most precise exact diagonalization results available. For the Anderson problem, we find a critical value of the disorder which is 0.9 % off the most precise available numerical value already in 5 spatial dimensions, while for the many-body localized phase of the Heisenberg model with random fields the critical disorder hc=4.0 ±0.3 is strikingly close to the most recent results obtained by exact diagonalization. In both cases we obtain a critical exponent ν =1 . In the Anderson case, the latter does not show dependence on the dimensionality, as it is common within mean-field approximations. We discuss the relevance of the correlations between the shortest paths for both the single- and many-body problems, and comment on the connections of our results with the problem of directed polymers in random medium.
Milde, Frank; R{ö}mer, Rudolf A.
1998-01-01
Recently, a metal-insulator transition (MIT) was found in the anisotropic Anderson model of localization by transfer-matrix methods (TMM). This MIT has been also investigated by multifractal analysis (MFA) and the same critical disorders $W_c$ have been obtained within the accuracy of the data. We now employ energy level statistics (ELS) to further characterize the MIT. We find a crossover of the nearest-neighbor level spacing distribution $P(s)$ from GOE statistics at small disorder indicati...
Daley, P; Wortis, R
2016-05-01
Non-interacting systems with bounded disorder have been shown to exhibit sharp density of state peaks at the band edge which coincide with an energy range of abruptly suppressed localization. Recent work has shown that these features also occur in the presence of on-site interactions in ensembles of two-site Anderson-Hubbard systems at half filling. Here we demonstrate that this effect in interacting systems persists away from half filling, and moreover that energy regions with suppressed localization continue to appear in ensembles of larger systems despite a loss of sharp features in the density of states. PMID:27022884
Local excitations in mean field spin glasses
Krzakala, F.; G.PARISI()
2003-01-01
We address the question of geometrical as well as energetic properties of local excitations in mean field Ising spin glasses. We study analytically the Random Energy Model and numerically a dilute mean field model, first on tree-like graphs, equivalent to a replica symmetric computation, and then directly on finite connectivity random lattices. In the first model, characterized by a discontinuous replica symmetry breaking, we found that the energy of finite volume excitation is infinite where...
Abaie, Behnam; Hosseini, Seyed Rasoul; Karbasi, Salman; Mafi, Arash
2016-04-01
Impact of the boundaries on transversely localized modes of a truncated one-dimensional disordered optical lattice is numerically studied. The results show lower modal number density near the boundaries compared with the bulk, while the average decay rate of the tail of localized modes is the same near the boundaries as in the bulk. It is suggested that the perceived suppressed localization near the boundaries is due to a lower mode density: on average, it is less probable to excite a localized mode near the boundaries; however, once it is excited, its localization is with the same exponential decay rate as any other localized mode.
Gomes, Anderson S L; Pincheira, Pablo I R; Moura, André L; Gagné, Mathieu; Kashyap, Raman; Raposo, Ernesto P; de Araújo, Cid B
2016-01-01
The analogue of the paramagnetic to spin-glass phase transition in disordered magnetic systems, leading to the phenomenon of replica symmetry breaking, has been recently demonstrated in a two-dimensional random laser consisting of an organic-based amorphous solid-state thin film. We report here the first demonstration of replica symmetry breaking in a one-dimensional photonic system consisting of an erbium-doped random fiber laser operating in the continuous-wave regime based on a unique random fiber grating system, which plays the role of the random scatterers and operates in the Anderson localization regime. The clear transition from a photonic paramagnetic to a photonic spin glass phase, characterized by the probability distribution function of the Parisi overlap, was verified and characterized. In this unique system, the radiation field interacts only with the gain medium, and the fiber grating, which provides the disordered feedback mechanism, does not interfere with the pump.
Steinigeweg, Robin [Institut fuer Theoretische Physik, Technische Universitaet Braunschweig, Mendelsohnstrasse 3, D-38106 Braunschweig (Germany); Niemeyer, Hendrik; Gemmer, Jochen, E-mail: r.steinigeweg@tu-bs.d, E-mail: jgemmer@uos.d [Fachbereich Physik, Universitaet Osnabrueck, Barbarastrasse 7, D-49069 Osnabrueck (Germany)
2010-11-15
Single-particle transport in disordered potentials is investigated at scales below the localization length. The dynamics at those scales is concretely analyzed for the three-dimensional Anderson model with Gaussian on-site disorder. This analysis particularly includes the dependence of characteristic transport quantities on the amount of disorder and the energy interval, e.g. the mean free path that separates ballistic and diffusive transport regimes. For these regimes mean velocities and diffusion constants are quantitatively given. Using the Boltzmann equation in the limit of weak disorder, we reveal the known energy dependences of transport quantities. By the application of the time-convolutionless projection operator technique in the limit of strong disorder, we obtain evidence for much less pronounced energy dependences. All our results are partially confirmed by the numerically exact solution of the time-dependent Schroedinger equation or by approximative numerical integrators. A comparison with other findings in the literature is also provided.
Anderson localization of light in a colloidal suspension (TiO2@silica).
Jimenez-Villar, Ernesto; da Silva, Iran F; Mestre, Valdeci; de Oliveira, Paulo C; Faustino, Wagner M; de Sá, Gilberto F
2016-06-01
In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition. PMID:26804337
Anderson localization of light in a colloidal suspension (TiO2@silica)
Jimenez-Villar, Ernesto; da Silva, Iran F.; Mestre, Valdeci; de Oliveira, Paulo C.; Faustino, Wagner M.; de Sá, Gilberto F.
2016-05-01
In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition.In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07540h
Anderson localization and its ramifications disorder, phase coherence and electron correlations
Kettemann, S
2003-01-01
The phenomenon of localization of the electronic wave function in a random medium can be regarded as the key manifestation of quantum coherence in a condensed matter system. As one of the most remarkable phenomena in condensed matter physics discovered in the 20th century, the localization problem is an indispensable part of the theory of the quantum Hall effects and rivals superconductivity in its significance as a manifestation of quantum coherence at a macroscopic scale. The present volume, written by some of the leading experts in the field, is intended to highlight some of the recent progress in the field of localization, with particular emphasis on the effect of interactions on quantum coherence. The chapters are written in textbook style and should serve as a reliable and thorough introduction for advanced students or researchers already working in the field of mesoscopic physics.
Measurement-induced disturbance near Anderson localization in one-dimensional systems
We study the localization transition in several typical one-dimensional single-particle systems by means of measurement-induced disturbance (MID). The results show that the MID presents a rapid drop around the boundary between the localized state and extended ones, and the corresponding first-order derivative exhibits a behavior of divergence around the critical point for deterministic on-site potential systems (e.g. the quasi-periodic model). These characteristics can capture a phase diagram as well as the traditional method. For the non-deterministic on-site systems (e.g. the random dimer model), the states around the resonant energies possess relatively large values for MID, which means that they are extended. In addition, as the random potential ϵ b exceeds the critical value, the states possessing a large MID vanish completely. These results show that MID can be useful in detecting localization transition in these typical one-dimensional systems. (paper)
Anderson localization at the edge of a 2D topological insulator
Khalaf, Eslam; Ostrovsky, Pavel
We study transport via edge modes in a disordered 2D topological insulator allowing for the presence of non-protected diffusive channels in addition to the topologically protected edge channels. This scenario can be realized at the interface between two quantum Hall system, in a Weyl semimetal in a magnetic field or at the edge of a quantum spin Hall system. The edge transport is described by a one-dimensional field theory in the form of a supersymmetric non-linear sigma model with a topological term. The transfer-matrix formalism is employed to map the problem to the problem of finding the eigenfunctions of a certain operator on a symmetric superspace. The latter problem is solved exactly for all symmetry classes, enabling us to obtain the full counting statistics and mesoscopic conductance fluctuations in the system. Our main finding is that disorder is much more effective in localizing the diffusive (non-protected) channels in the presence of topologically protected ones. This manifests itself as a suppression of the shot noise and conductance fluctuations at scales much shorter than the localization length.
Local excitations of a spin glass in a magnetic field
Lamarcq, J.; Bouchaud, J.-P.; Martin, O. C.
2003-07-01
We study the minimum energy clusters (MEC) above the ground state for the 3-d Edwards-Anderson Ising spin glass in a magnetic field. For fields B below 0.4, we find that the field has almost no effect on the excitations that we can probe, of volume V⩽64. As found previously for B=0, their energies decrease with V, and their magnetization remains very small (even slightly negative). For larger fields, both the MEC energy and magnetization grow with V, as expected in a paramagnetic phase. However, all results appear to scale as BV (instead of B(V) as expected from droplet arguments), suggesting that the spin glass phase is destroyed by any small field. Finally, the geometry of the MEC is completely insensitive to the field, giving further credence that they are lattice animals, in the presence or the absence of a field.
Anderson, Karl F.
1994-01-01
Four-wire-probe concept applied to electrical-resistance transducers. Anderson current loop is excitation-and-signal-conditioning circuit suitable for use with strain gauges, resistance thermometers, and other electrical-resistance transducers mounted in harsh environments. Used as alternative to Wheatstone bridge. Simplifies signal-conditioning problem, enabling precise measurement of small changes in resistance of transducer. Eliminates some uncertainties in Wheatstone-bridge resistance-change measurements in flight research. Current loop configuration makes effects of lead-wire and contact resistances insignificantly small. Also provides output voltage that varies linearly with change in gauge resistance, and does so at double sensitivity of Wheatstone bridge.
Quantum entanglement of localized excited states at finite temperature
Caputa, Pawel; Simón, Joan; Štikonas, Andrius(School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, King’s Buildings, Edinburgh, EH9 3FD, U.K.); Takayanagi, Tadashi
2015-01-01
In this work we study the time evolutions of (Renyi) entanglement entropy of locally excited states in two dimensional conformal field theories (CFTs) at finite temperature.We consider excited states created by acting with local operators on thermal states and give both field theoretic and holographic calculations. In free field CFTs, we find that the growth of Renyi entanglement entropy at finite temperature is reduced compared to the zero temperature result by a small quantity proportional ...
Bachelard, Nicolas; Sebbah, Patrick; Vanneste, Christian
2014-01-01
We use time-domain numerical simulations of a two-dimensional (2D) scattering system to study the interaction of a collection of emitters resonantly coupled to an Anderson-localized mode. For a small electric field intensity, we observe the strong coupling between the emitters and the mode, which is characterized by linear Rabi oscillations. Remarkably, a larger intensity induces non-linear interaction between the emitters and the mode, referred to as the dynamical Stark effect, resulting in non-linear Rabi oscillations. The transition between both regimes is observed and an analytical model is proposed which accurately describes our numerical observations.
Quantum dimensions from local operator excitations in the Ising model
Caputa, Pawel
2016-01-01
We compare the time evolution of entanglement measures after local operator excitation in the critical Ising model with predictions from conformal field theory. For the spin operator and its descendants we find that Renyi entropies of a block of spins increase by a constant that matches the logarithm of the quantum dimension of the conformal family. However, for the energy operator we find a small constant contribution that differs from the conformal field theory answer equal to zero. We argue that the mismatch is caused by the subtleties in the identification between the local operators in conformal field theory and their lattice counterpart. Our results indicate that evolution of entanglement measures in locally excited states not only constraints this identification, but also can be used to extract non-trivial data about the conformal field theory that governs the critical point. We generalize our analysis to the Ising model away from the critical point, states with multiple local excitations, as well as t...
Transverse Chiral Optical Forces by Locally Excited Surface Plasmon Polaritons
Alizadeh, M H
2015-01-01
Recently the new concepts of transverse spin angular momentum and Belinfante spin momentum of evanescent waves have drawn considerable attention. Here, we investigate these novel physical properties of electromagnetic fields in the context of locally excited surface plasmon polaritons. We demonstrate, both analytically and numerically, that locally excited surface plasmon polaritons possess transverse spin angular momentum and Belinfante momentum with rich and non-trivial characteristics. We also show that the transverse spin angular momentum of locally excited surface plasmon polaritons leads to the emergence of transverse chiral forces in opposite directions for chiral objects of different handedness. The magnitude of such a transverse force is comparable to the optical gradient force and scattering forces. This finding may pave the way for realization of optical separation of chiral biomolecules.
Quantum entanglement of localized excited states at finite temperature
Caputa, Pawel; Simón, Joan; Štikonas, Andrius; Takayanagi, Tadashi
2015-01-01
In this work we study the time evolutions of (Renyi) entanglement entropy of locally excited states in two dimensional conformal field theories (CFTs) at finite temperature. We consider excited states created by acting with local operators on thermal states and give both field theoretic and holographic calculations. In free field CFTs, we find that the growth of Renyi entanglement entropy at finite temperature is reduced compared to the zero temperature result by a small quantity proportional to the width of the localized excitations. On the other hand, in finite temperature CFTs with classical gravity duals, we find that the entanglement entropy approaches a characteristic value at late time. This behaviour does not occur at zero temperature. We also study the mutual information between the two CFTs in the thermofield double (TFD) formulation and give physical interpretations of our results.
Quantum Entanglement of Localized Excited States at Finite Temperature
Caputa, Pawel; Stikonas, Andrius; Takayanagi, Tadashi
2014-01-01
In this work we study the time evolutions of (Renyi) entanglement entropy of locally excited states in two dimensional conformal field theories (CFTs) at finite temperature. We consider excited states created by acting with local operators on thermal states and give both field theoretic and holographic calculations. In free field CFTs, we find that the growth of Renyi entanglement entropy at finite temperature is reduced compared to the zero temperature result by a small quantity proportional to the width of the localized excitations. On the other hand, in finite temperature CFTs with classical gravity duals, we find that the entanglement entropy approaches a characteristic value at late time. This behaviour does not occur at zero temperature. We also study the mutual information between the two CFTs in the thermofield double (TFD) formulation and give physical interpretations of our results.
Efficiency of local surface plasmon polariton excitation on ridges
Radko, I.P.; Bozhevolnyi, S.I.; Brucoli, G.;
2008-01-01
The issue of efficient local coupling of light into surface plasmon polariton (SPP) modes is an important concern in miniaturization of plasmonic components. Here we present experimental and numerical investigations of efficiency of local SPP excitation on gold ridges of rectangular profile...... positioned on a gold film. The excitation is accomplished by illuminating the metal surface normally with a focused laser beam. Wavelength dependence and dependence of the efficiency on geometrical parameters of ridges are examined. Using leakage radiation microscopy, the efficiency of ˜20% is demonstrated...... experimentally. Numerical simulations based on Green’s tensor approach are in good agreement with the experiment and allow suggesting an optimization of parameters for improving the efficiency of SPP excitation....
Parametric Excitation, Localization and Synchronization in Nonlinear Hydrodynamical Systems
Goldobin, Denis S
2008-01-01
The dissertation contains 4 original chapters: 1) Parametric excitation of Soret-driven convection of binary mixture in a horizontal porous layer. 2) Soret-driven convection in a horizontal porous layer from a heat or concentration source. 3) Localization of convective flows under randomly inhomogeneous heating. 4) Synchrony of nonlinear systems driven by common noise.
Excitation and geometrically matched local encoding of curved slices.
Weber, Hans; Gallichan, Daniel; Schultz, Gerrit; Cocosco, Chris A; Littin, Sebastian; Reichardt, Wilfried; Welz, Anna; Witschey, Walter; Hennig, Jürgen; Zaitsev, Maxim
2013-05-01
In this work, the concept of excitation and geometrically matched local in-plane encoding of curved slices (ExLoc) is introduced. ExLoc is based on a set of locally near-orthogonal spatial encoding magnetic fields, thus maintaining a local rectangular shape of the individual voxels and avoiding potential problems arising due to highly irregular voxel shapes. Unlike existing methods for exciting curved slices based on multidimensional radiofrequency-pulses, excitation and geometrically matched local encoding of curved slices does not require long duration or computationally expensive radiofrequency-pulses. As each encoding field consists of a superposition of potentially arbitrary (spatially linear or nonlinear) magnetic field components, the resulting field shape can be adapted with high flexibility to the specific region of interest. For extended nonplanar structures, this results in improved relevant volume coverage for fewer excited slices and thus increased efficiency. In addition to the mathematical description for the generation of dedicated encoding fields and data reconstruction, a verification of the ExLoc concept in phantom experiments and examples for in vivo curved single and multislice imaging are presented. PMID:22711656
无
2007-01-01
@@ Design Concept: "Wuhan Blue Prototype" A highlight of the concept is its integration with the local neighbourhood.The building and site planning will be coordinated with the existing planned facilities with a great lawn leading up from the community entrance toward a community gym and shopping centre. The Blue Sky Prototype itself is planned as an open-air network of pedestrian streets and public gardens at ground level winding up to vertical floor plates. The front doors of each unit will open to wide open-air streets and the sky.
Causal Evolutions of Bulk Local Excitations from CFT
Goto, Kanato; Takayanagi, Tadashi
2016-01-01
Bulk localized excited states in an AdS spacetime can be constructed from Ishibashi states with respect to the global conformal symmetry in the dual CFT. We study boundary two point functions of primary operators in the presence of bulk localized excitations in two dimensional CFTs. From two point functions in holographic CFTs, we observe causal propagations of radiations when the mass of dual bulk scalar field is close to the BF bound. This behavior for holographic CFTs is consistent with the locality and causality in classical gravity duals. We also show that this cannot be seen in free fermion CFTs. Moreover, we find that the short distance behavior of two point functions is universal and obeys the relation which generalizes the first law of entanglement entropy.
Local structural excitations and critical temperature of supported superconducting oxides
High resolution IR spectra for the following complex oxides: La2CuO4, Nd2CuO4, YBa2Cu3O7-x, BaBiO3, HgCaBaCuO (at cations ratio 1223) were obtained for studying the role of oxygen sublattice in formation of electrophysical properties of superconducting oxide ceramics. Frequencies of vibration spectra sensitive to lattice distortions, oxygen content and occurrence of its excited states, were revealed. The assumption on local structural excitations and role of donor-acceptor interactions in formation of high-temperature superconductivity was confirmed
Local excitations in mean-field spin glasses
Krzakala, F.; Parisi, G.
2004-06-01
We address the question of geometrical as well as energetic properties of local excitations in mean-field Ising spin glasses. We study analytically the Random Energy Model and numerically a dilute mean-field model, first on tree-like graphs, equivalent to a replica-symmetric computation, and then directly on finite-connectivity random lattices. In the first model, characterized by a discontinuous replica symmetry breaking, we found that the energy of finite-volume excitation is infinite, whereas in the dilute mean-field model, described by a continuous replica symmetry breaking, it slowly decreases with sizes and saturates at a finite value, in contrast with what would be naively expected. The geometrical properties of these excitations are similar to those of lattice animals or branched polymers. We discuss the meaning of these results in terms of replica symmetry breaking and also possible relevance in finite-dimensional systems.
Localized excitations in superconducting point contacts: probing the Andreev doublet
The Josephson effect describes the coherent coupling between superconductors and the resulting supercurrent. Microscopically, it arises from the existence of discrete quasiparticle states, localized at the weak link, the Andreev bound states. They come in doublets in each conduction channel of the weak link, with energies symmetric about the Fermi energy and opposite supercurrents. Each Andreev doublet gives rise to four states: the ground state |-> and the excited state |+>, with even parity, and the excited odd states |↑> and |↓>. Is it possible to address and control Andreev doublets? This thesis describes two sets of experiments designed to answer this question using the most basic Josephson element, a one-atom contact between two superconducting electrodes. In a first experiment, we have observed and characterized the excited odd states |↑> and |↓>. As expected for a spin-degenerate system, they do not carry supercurrent. In this experiment the excitation was uncontrolled and resulted from trapping of spurious quasiparticles. We have measured the lifetime of the odd states: under some condition, it is found to exceed 100 μs. The second experiment is a photon-absorption spectroscopy of the Andreev doublet. It was performed by using a Josephson junction as an integrated on-chip microwave emitter and detector. The observed Andreev transitions correspond to excitation from the ground state |->to the excited even state |+>, and are well accounted for by our quantum model. This result opens the way to coherent manipulation of this two level system. The direct observation of the excited Andreev state, either by quasiparticle-injection or photon-absorption, strongly supports the mesoscopic theory of the Josephson effect. It shows that in addition to the phase difference, each channel of a Josephson weak link possesses an internal fermionic degree of freedom. It could be used to code information in a novel type of superconducting qubit. (author)
Enhanced Electromagnetic Chirality by Locally Excited Surface Plasmon Polaritons
Alizadeh, M H
2015-01-01
The possibility to enhance chiral light-matter interactions through plasmonic nanostructures provides entirely new opportunities for greatly improving the detection limits of chiroptical spectroscopies down to the single molecule level. The most pronounced of these chiral interactions occur in the ultraviolet (UV) range of the electromagnetic spectrum, which is difficult to access with conventional localized plasmon resonance based sensors. Although Surface Plasmon Polaritons (SPPs) on noble metal films can sustain resonances in the desired spectral range, their transverse magnetic nature has been an obstacle for enhancing chiroptical effects. Here we demonstrate, both analytically and numerically, that SPPs excited by near-field sources can exhibit rich and non-trivial chiral characteristics. In particular, we show that the excitation of SPPs by a chiral source not only results in a locally enhanced optical chirality but also achieves manifold enhancement of net optical chirality. Our finding that SPPs facil...
Direct observation of localized dipolar excitations on rough nanostructured surfaces
Bozhevolnyi, Sergey I.; Markel, V.A.; Coello, V.;
1998-01-01
Using a photon scanning tunneling microscope (operating alternatively at the wavelengths of 594 and 633 nm) with shear-force feedback we image the topography of silver colloid fractals simultaneously with a near-field intensity distribution. We observe that near-field optical images exhibit...... spatially localized (within 150-250 nm) intensity enhancement by one to two orders of magnitude. These bright light spots are found to be sensitive to the light wavelength, polarization, and angle of incidence. We relate the observed phenomenon to the localization of resonant dipolar excitations in random...
Excitations and management of the nonlinear localized gap modes
Bishwajyoti Dey
2015-11-01
We discuss about the theory of nonlinear localized excitations, such as soliton and compactons in the gap of the linear spectrum of the nonlinear systems. We show how the gap originates in the linear spectrum using examples of a few systems, such as nonlinear lattices, Bose–Einstein condensates in optical lattice and systems represented by coupled nonlinear evolution equations. We then analytically show the excitation of solitons and compacton-like solutions in the gap of the linear spectrum of a system of coupled Korteweg–de Vries (KdV) equations with linear and nonlinear dispersions. Finally, we discuss about the theory of Feshbach resonance management and dispersion management of the soliton solutions.
Allen, Roland E
2013-01-01
The particle recently discovered by the CMS and ATLAS collaborations at CERN is almost certainly a Higgs boson, fulfilling a quest that can be traced back to three seminal high energy papers of 1964, but which is intimately connected to ideas in other areas of physics that go back much further. One might oversimplify the history of the features which (i) give mass to the W and Z particles that mediate the weak nuclear interaction, (ii) effectively break gauge invariance, (iii) eliminate physically unacceptable Nambu-Goldstone bosons, and (iv) give mass to fermions (like the electron) by collectively calling them the London-Anderson-Englert-Brout-Higgs-Guralnik-Hagen-Kibble-Weinberg mechanism. More important are the implications for the future: a Higgs boson appears to point toward supersymmetry, since new physics is required to protect its mass from enormous quantum corrections, while the discovery of neutrino masses seems to point toward grand unification of the nongravitational forces.
Local excitation and collection in polymeric fluorescent microstructures
Henrique, Franciele Renata; Mendonca, Cleber Renato
2016-04-01
Integrated photonics has gained attention in recent years due to its wide range of applications which span from biology to optical communications. The use of polymer-based platforms for photonic devices is of great interest because organic compounds can be easily incorporated to polymers, enabling modifications to the system physical properties. The two-photon polymerization technique has emerged as an interesting tool for the production of three-dimensional polymeric microstructures. However, for their further incorporation in photonic devices it is necessary to develop methods to perform optical excitation and signal collection on such microstructures. With such purpose, we demonstrate approaches to perform local excitation and collection in polymeric microstructures doped with fluorescent dyes, employing tapered fibers. The obtained results indicate that fiber tapers are suitable to couple light in and out of fluorescent polymeric microstructures, paving the way for their incorporation in photonic devices. We also show that microstructures doped with more than one dye can be used as built-in broadband light sources to photonic circuits and their emission spectrum can be tuned by the right choice of the excitation position.
Damage Localization of Offshore Platforms Under Ambient Excitation
杨和振; 李华军; 王树青
2003-01-01
In this paper Nondestructive Damage Detection (NDD) for offshore platforms is investigated under operational conditions. As is known, there is no easy way to measure ambient excitation, so damage detection methods based on ambient excitation have become very vital for the Structural Health Monitoring (SHM) of offshore platforms. The modal parameters (natural frequencies, damping ratios and mode shapes) are identified from structural response data with the Natural Excitation Technique (NExT) in conjunction with the Eigensystem Realization Algorithm (ERA). A new method of damage detection is presented, which utilizes the invariance property of element modal strain energy. This method is to assign element modal strain energy to two parts, and defines two damage detection indicators. One is compression modal strain energy change ratio (CMSECR); the other is flexural modal strain energy change ratio (FMSECR). The present modal strain energy is obtained by incomplete modal shape and structural stiffness matrix. Structural health monitoring is thus accomplished via monitoring the elemental CMSECR and FMSECR. Several damage cases are simulated by an offshore platform numerical model, and presented to illustrate the utility of the proposed method. According to the damage localization results, the proposed method is shown to be effective and precise for complex structural damage detection.
Quantum Entanglement of Locally Excited States in Maxwell Theory
Nozaki, Masahiro
2016-01-01
In 4 dimensional Maxwell gauge theory, we study the changes of (Renyi) entangle-ment entropy which are defined by subtracting the entropy for the ground state from the one for the locally excited states generated by acting with the gauge invariant local operators on the state. The changes for the operators which we consider in this paper reflect the electric-magnetic duality. The late-time value of changes can be interpreted in terms of electromagnetic quasi-particles. When the operator constructed of both electric and magnetic fields acts on the ground state, it shows that the operator acts on the late-time structure of quantum entanglement differently from free scalar fields.
Parametric excitation of multiple resonant radiations from localized wavepackets
Conforti, Matteo; Mussot, Arnaud; Kudlinski, Alexandre
2015-01-01
Fundamental physical phenomena such as laser-induced ionization, driven quantum tunneling, Faraday waves, Bogoliubov quasiparticle excitations, and the control of new states of matter rely on time-periodic driving of the system. A remarkable property of such driving is that it can induce the localized (bound) states to resonantly couple to the continuum. Therefore experiments that allow for enlightening and controlling the mechanisms underlying such coupling are of paramount importance. We implement such an experiment in a special fiber optics system characterized by a dispersion oscillating along the propagation coordinate, which mimics "time". The quasi-momentum associated with such periodic perturbation is responsible for the efficient coupling of energy from the localized wave-packets sustained by the fiber nonlinearity into free-running linear dispersive waves (continuum), at multiple resonant frequencies. Remarkably, the observed resonances can be explained by means of a unified approach, regardless of ...
Raj, S; Hashimoto, D; Matsui, H; Souma, S; Sato, T; Takahashi, T; Sarma, D D; Mahadevan, Priya; Oishi, S
2006-04-14
The electronic structure of the insulating sodium tungsten bronze, Na(0.025)WO(3), is investigated by high-resolution angle-resolved photoemission spectroscopy. We find that near-E(F) states are localized due to the strong disorder arising from random distribution of Na+ ions in the WO(3) lattice, which makes the system insulating. The temperature dependence of photoemission spectra provides direct evidence for polaron formation. The remnant Fermi surface of the insulator is found to be the replica of the real Fermi surface in the metallic system. PMID:16712121
Purpose: To evaluate the rates of tumor downstaging after preoperative chemoradiation for locally advanced rectal cancer. Materials and Methods: Preoperative chemoradiotherapy (CTX/XRT) that delivered 45 Gy in 25 fractions over 5 weeks with continuous infusion 5-fluorouracil (300 mg/m2/day) was given to 117 patients. The pretreatment stage distribution, as determined by endorectal ultrasound (u), included uT2N0 in 2%, uT3N0 in 47%, uT3N1 in 49%, and uT4N0 in 2% of cases; endorectal ultrasound was not performed in 13% of cases (15 patients). Approximately 6 weeks after completion of CTX/XRT, surgery was performed. Results: The pathological tumor stages were Tis-2N0 in 26%, T2N1 in 5%, T3N0 in 21%, T3N1 in 15%, T4N0 in 5%, and T4N1 in 1%; a complete response (CR) to preoperative CTX/XRT was pathologically confirmed in 32 (27%) of patients. Tumor downstaging occurred in 72 (62%) cases. Only 3% of cases had pathologic evidence of progressive disease. Pretreatment tumor size (1 T-stage level was accomplished in 45% of those downstaged. Overall, a sphincter-saving (SP) procedure was possible in 59% of patients and an abdominoperineal resection (APR) was required in 41% of cases. Factors predictive of SP included downstaging (p 40 years (p 6 cm from the anal verge, SP was performed in 14 of the 15 (93%) patients with a CR and 32 of 33 (97%) of patients with residual disease (p < 0.00004). Conclusions: Significant tumor downstaging results from preoperative chemoradiation allowing sphincter sparing surgery in over 40% of patients whose tumors were located < 6 cm from the anal verge and who otherwise would have required colostomy
Probing the Locality of Excited States with Linear Algebra.
Etienne, Thibaud
2015-04-14
This article reports a novel theoretical approach related to the analysis of molecular excited states. The strategy introduced here involves gathering two pieces of physical information, coming from Hilbert and direct space operations, into a general, unique quantum mechanical descriptor of electronic transitions' locality. Moreover, the projection of Hilbert and direct space-derived indices in an Argand plane delivers a straightforward way to visually probe the ability of a dye to undergo a long- or short-range charge-transfer. This information can be applied, for instance, to the analysis of the electronic response of families of dyes to light absorption by unveiling the trend of a given push-pull chromophore to increase the electronic cloud polarization magnitude of its main transition with respect to the size extension of its conjugated spacer. We finally demonstrate that all the quantities reported in this article can be reliably approximated by a linear algebraic derivation, based on the contraction of detachment/attachment density matrices from canonical to atomic space. This alternative derivation has the remarkable advantage of a very low computational cost with respect to the previously used numerical integrations, making fast and accurate characterization of large molecular systems' excited states easily affordable. PMID:26574379
Development of a radio frequency excited local impedance probe
Local void fraction measurements were made with a Karlsruhe type impedance probe. The probe was operated at radiofrequency to minimize sensitivity to liquid phase resistivity. Two types of signal thresholding were used: level and derivative. A dual beam X-ray system was used as a calibration standard for the radio frequency excited impedance probe. Calibration was performed in vertical air/water flows. Derivative thresholding was found to be preferable to level thresholding, however, in both schemes hydrodynamic and surface tension effects were observed below a liquid superficial velocity of 0.5 m/s. Table salt (NaCl) was added to the water to verify the probe's response to changing water resistivity. Derivative thresholding appeared to work quite well but level thresholding was found to be inadequate due to the change in capacitance. (orig.)
Localized nonlinear excitations in diffusive Hindmarsh-Rose neural networks.
Moukam Kakmeni, F M; Inack, E M; Yamakou, E M
2014-05-01
We study localized nonlinear excitations in diffusive Hindmarsh-Rose neural networks. We show that the Hindmarsh-Rose model can be reduced to a modified Complex Ginzburg-Landau equation through the application of a perturbation technique. We equally report on the presence of envelop solitons of the nerve impulse in this neural network. From the biological point of view, this result suggests that neurons can participate in a collective processing of information, a relevant part of which is shared over all neurons but not concentrated at the single neuron level. By employing the standard linear stability analysis, the growth rate of the modulational instability is derived as a function of the wave number and systems parameters. PMID:25353873
New localized excitations in a (2+1)-dimensional Broer-Kaup system
Bai Cheng-Lin; Liu Xi-Qiang; Zhao Hong
2005-01-01
Starting with the extended homogeneous balance method and a variable separation approach, a general variable separation solution of the Broer-Kaup system is derived. In addition to the usual localized coherent soliton excitations like dromions, lumps, rings, breathers, instantons, oscillating soliton excitations, peakon and fractal localized solutions,some new types of localized excitations, such as compacton and folded excitations, are obtained by introducing appropriate lower-dimensional piecewise smooth functions and multiple-valued functions, and some interesting novel features of these structures are revealed.
Efficiency of local surface plasmon polariton excitation on ridges
Radko, Ilya; Bozhevolnyi, Sergey I.; Boltasseva, Alexandra;
2008-01-01
We investigate experimentally and numerically the efficiency of surface plasmon polariton excitation by a focused laser beam using gold ridges. The dependence of the efficiency on geometrical parameters of ridges and wavelength dependence are examined. The experimental measurements accomplished...
Interview with Philip W. Anderson
Phil Anderson, Professor of Physics at Princeton University, has devoted his career to research in theoretical physics. He is a member of the National Academy of Science and the American Academy of Arts and Sciences, a foreign member of the Royal Society, and a foreign associate of the Accademia Lincei in Rome. The Americal Physical Society awarded him the Oliver E. Buckley Solid State Physics Prize in 1964. In 1977 he won the Nobel Prize in Physics with J.H. van Vleck and N.F. Mott. His work has encompassed a broad range of subjects: quantum theory of condensed matter, broken symmetry, transport theory and localization, random statistical systems, spectral line broadening, superfluidity in helium and neutron stars, magnetism, and superconductivity. His avocations include ''hiking, the game of GO, Romanesque architecture, and the human condition.'' In this interview he explains his RVB theory of the oxide superconductors and its historical context
Local density approximation for exchange in excited-state density functional theory
Harbola, Manoj K.; Samal, Prasanjit
2004-01-01
Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies.
Miles, J. A.; Das, Diptaranjan; Simmons, Z. J.; Yavuz, D. D.
2015-09-01
We experimentally demonstrate the localization of excitation between hyperfine ground states of 87Rb atoms to as small as λ /13 -wide spatial regions. We use ultracold atoms trapped in a dipole trap and utilize electromagnetically induced transparency (EIT) for the atomic excitation. The localization is achieved by combining a spatially varying coupling laser (standing wave) with the intensity dependence of EIT. The excitation is fast (150 ns laser pulses) and the dark-state fidelity can be made higher than 94% throughout the standing wave. Because the width of the localized regions is much smaller than the wavelength of the driving light, traditional optical imaging techniques cannot resolve the localized features. Therefore, to measure the excitation profile, we use an autocorrelation-like method where we perform two EIT sequences separated by a time delay, during which we move the standing wave.
Damage Localization and Quantification of Earthquake Excited RC-Frames
Skjærbæk, P.S.; Nielsen, Søren R.K.; Kirkegaard, Poul Henning;
In the paper a recently proposed method for damage localization and quantification of RC-structures from response measurements is tested on experimental data. The method investigated requires at least one response measurement along the structure and the ground surface acceleration. Further, the t...
Non-local effects of edge excitations in the quantum Hall regime
Deviatov, E. V.; Lorke, A; Biasiol, G.; Sorba, L.
2010-01-01
We use a novel sample geometry to study non-local effects of edge excitations in the integer quantum Hall effect regime. We find that the condition of local equilibrium at the quantum Hall edge is affected by the diffusion of dynamically polarized nuclei. Our analysis indicates, that the nuclear diffusion is effectively one-dimensional in the present experiment.
Multiple-Resonance Local Wave Functions for Accurate Excited States in Quantum Monte Carlo.
Zulfikri, Habiburrahman; Amovilli, Claudio; Filippi, Claudia
2016-03-01
We introduce a novel class of local multideterminant Jastrow-Slater wave functions for the efficient and accurate treatment of excited states in quantum Monte Carlo. The wave function is expanded as a linear combination of excitations built from multiple sets of localized orbitals that correspond to the bonding patterns of the different Lewis resonance structures of the molecule. We capitalize on the concept of orbital domains of local coupled-cluster methods, which is here applied to the active space to select the orbitals to correlate and construct the important transitions. The excitations are further grouped into classes, which are ordered in importance and can be systematically included in the Jastrow-Slater wave function to ensure a balanced description of all states of interest. We assess the performance of the proposed wave function in the calculation of vertical excitation energies and excited-state geometry optimization of retinal models whose π → π* state has a strong intramolecular charge-transfer character. We find that our multiresonance wave functions recover the reference values of the total energies of the ground and excited states with only a small number of excitations and that the same expansion can be flexibly used at very different geometries. Furthermore, significant computational saving can also be gained in the orbital optimization step by selectively mixing occupied and virtual orbitals based on spatial considerations without loss of accuracy on the excitation energy. Our multiresonance wave functions are therefore compact, accurate, and very promising for the calculation of multiple excited states of different character in large molecules. PMID:26761421
Nuclear charge-exchange excitations in localized covariant density functional theory
The recent progress in the studies of nuclear charge-exchange excitations with localized covariant density functional theory is briefly presented, by taking the fine structure of spin-dipole excitations in 16O as an example. It is shown that the constraints introduced by the Fock terms of the relativistic Hartree-Fock scheme into the particle-hole residual interactions are straightforward and robust. (authors)
Nuclear charge-exchange excitations in localized covariant density functional theory
Liang, H Z; Nakatsukasa, T; Niu, Z M; Ring, P; Roca-Maza, X; Van Giai, N; Zhao, P W
2014-01-01
The recent progress in the studies of nuclear charge-exchange excitations with localized covariant density functional theory is briefly presented, by taking the fine structure of spin-dipole excitations in 16O as an example. It is shown that the constraints introduced by the Fock terms of the relativistic Hartree-Fock scheme into the particle-hole residual interactions are straightforward and robust.
Schrauben, Joel N.; Akdag, Akin; Wen, Jin; Havlas, Zdenek; Ryerson, Joseph L.; Smith, Millie B.; Michl, Josef; Johnson, Justin C.
2016-05-26
Two isomers of both the lowest excited singlet (S1) and triplet (T1) states of the directly para, para'-connected covalent dimer of the singlet-fission chromophore 1,3-diphenylisobenzofuran have been observed. In one isomer, excitation is delocalized over both halves of the dimer, and in the other, it is localized on one or the other half. For a covalent dimer in solution, such 'excitation isomerism' is extremely rare. The vibrationally relaxed isomers do not interconvert, and their photophysical properties, including singlet fission, differ significantly.
Lithuania 1940 / Herbert Foster Anderson
Foster Anderson, Herbert
2004-01-01
Stseenid Leedu ennesõjaaegsest pealinnast Kaunasest briti ärimehe H. Foster Andersoni silme läbi 1940. aastal. Lühikokkuvõte raamatust: Foster Anderson, Herbert. Borderline Russia. London : Cresset press, 1942
The Price-Anderson Act establishes nuclear liability law in the United States. First passed in 1957, it has influenced other nuclear liability legislation around the world. The insurer response the nuclear accident at Three Mile Island in 1979 demonstrates the application of the Act in a real life situation. The Price-Anderson Act is scheduled to be renewed in 2002, and the future use of commercial nuclear power in tge United States will be influenced by this renewal. (author)
Nagesh, Jayashree; Brumer, Paul; Izmaylov, Artur F
2016-01-01
We extend the localized operator partitioning method (LOPM) [J. Nagesh, A.F. Izmaylov, and P. Brumer, J. Chem. Phys. 142, 084114 (2015)] to the time-dependent density functional theory (TD-DFT) framework to partition molecular electronic energies of excited states in a rigorous manner. A molecular fragment is defined as a collection of atoms using Stratman-Scuseria-Frisch atomic partitioning. A numerically efficient scheme for evaluating the fragment excitation energy is derived employing a resolution of the identity to preserve standard one- and two-electron integrals in the final expressions. The utility of this partitioning approach is demonstrated by examining several excited states of two bichromophoric compounds: 9-((1-naphthyl)-methyl)-anthracene and 4-((2-naphthyl)-methyl)-benzaldehyde. The LOPM is found to provide nontrivial insights into the nature of electronic energy localization that are not accessible using simple density difference analysis.
Localized Beampipe Heating due to $e^-$ Capture and Nuclear Excitation in Heavy Ion Colliders
Klein, Spencer R.
2000-01-01
At heavy ion colliders, two major sources of beam loss are expected to be $e^+e^-$ production, where the $e^-$ is bound to one of the nuclei, and photonuclear excitation and decay via neutron emission. Both processes alter the ions charged to mass ratio by well defined amounts, creating beams of particles with altered magnetic rigidity. These beams will deposit their energy in a localized region of the accelerator, causing localized heating, The size of the target region depends on the collid...
Excitation by Axon Terminal GABA Spillover in a Sound Localization Circuit.
Weisz, Catherine J C; Rubio, Maria E; Givens, Richard S; Kandler, Karl
2016-01-20
Synapses from neurons of the medial nucleus of the trapezoid body (MNTB) onto neurons of the lateral superior olive (LSO) in the auditory brainstem are glycinergic in maturity, but also GABAergic and glutamatergic in development. The role for this neurotransmitter cotransmission is poorly understood. Here we use electrophysiological recordings in brainstem slices from P3-P21 mice to demonstrate that GABA release evoked from MNTB axons can spill over to neighboring MNTB axons and cause excitation by activating GABAAR. This spillover excitation generates patterns of staggered neurotransmitter release from different MNTB axons resulting in characteristic "doublet" postsynaptic currents in LSO neurons. Postembedding immunogold labeling and electron microscopy provide evidence that GABAARs are localized at MNTB axon terminals. Photolytic uncaging of p-hydroxyphenacyl (pHP) GABA demonstrates backpropagation of GABAAR-mediated depolarizations from MNTB axon terminals to the soma, some hundreds of microns away. These somatic depolarizations enhanced somatic excitability by increasing the probability of action potential generation. GABA spillover excitation between MNTB axon terminals may entrain neighboring MNTB neurons, which may play a role in the developmental refinement of the MNTB-LSO pathway. Axonal spillover excitation persisted beyond the second postnatal week, suggesting that this mechanism may play a role in sound localization, by providing new avenues of communication between MNTB neurons via their distal axonal projections. Significance statement: In this study, a new mechanism of neuronal communication between auditory synapses in the mammalian sound localization pathway is described. Evidence is provided that the inhibitory neurotransmitter GABA can spill over between axon terminals to cause excitation of nearby synapses to further stimulate neurotransmitter release. Excitatory GABA spillover between inhibitory axon terminals may have important implications
Covalent bonding effect on the mean excitation energy of H2 with the local plasma model
Kamaratos, E.
1984-01-01
Chemical bonding is taken into account explicitly in the determination of the mean excitation energy (I) for stopping power of H2 with the local plasma approximation by employing molecular electronic wave functions for H2 for the first time. This procedure leads to a new value for IH2 that is higher than all accepted experimental and theoretical values.
Rasmussen, Kim; Christiansen, Peter Leth; Johansson, Magnus; Gaididei, Yuri B.; Mingaleev, S.F.
with nearest-neighbor coupling we discuss the stability of highly localized, "breather-like", excitations under the influence of thermal fluctuations. Numerical analysis shows that the lifetime of the breather is aln,aps finite and in a large parameter region inversely proportional to the noise...
Phil Anderson's Magnetic Ideas in Science
Coleman, Piers
2016-01-01
In Philip W. Anderson's research, magnetism has always played a special role, providing a prism through which other more complex forms of collective behavior and broken symmetry could be examined. I discuss his work on magnetism from the 1950s, where his early work on antiferromagnetism led to the pseudospin treatment of superconductivity - to the 70s and 80s, highlighting his contribution to the physics of local magnetic moments. Phil's interest in the mechanism of moment formation, and screening evolved into the modern theory of the Kondo effect and heavy fermions.
Potential-energy surfaces of local excited states from subsystem- and selective Kohn–Sham-TDDFT
Research highlights: ► Application of selective TDDFT for potential-energy surfaces. ► Improved eigenvector guesses for convergence speed-up. ► Intuitive single-orbital transition picture breaks down in adsorbate–surface model. ► Comparison of frozen-density embedding with classical point-charge models. ► Frozen-density embedding yields smooth potential-energy surfaces for adsorbate states. - Abstract: Calculating excited-state potential-energy surfaces for systems with a large number of close-lying excited states requires the identification of the relevant electronic transitions for several geometric structures. Time-dependent density functional theory (TDDFT) is very efficient in such calculations, but the assignment of local excited states of the active molecule can be difficult. We compare the results of the frozen-density embedding (FDE) method with those of standard Kohn–Sham density-functional theory (KS-DFT) and simpler QM/MM-type methods. The FDE results are found to be more accurate for the geometry dependence of excitation energies than classical models. We also discuss how selective iterative diagonalization schemes can be exploited to directly target specific excitations for different structures. Problems due to strongly interacting orbital transitions and possible solutions are discussed. Finally, we apply FDE and the selective KS-TDDFT to investigate the potential energy surface of a high-lying π → π∗ excitation in a pyridine molecule approaching a silver cluster.
Nonlinear Response of Localized Excitons: Effects of the Excitation-Induced Dephasing
Borri, Paola; Langbein, Wolfgang Werner; Birkedal, Dan;
1997-01-01
The polarization dependence of the ultrafast nonlinear response of localized excitons in GaAs/AlGaAs quantum wells has been investigated by spectrally resolved, transient four-wave mixing. The role of the excitation-induced dephasing in the delay dependence of the signal is discussed in detail. In...... particular, we show experimentally that the excitation-induced dephasing gives rise to a photon echo in inhomogeneous systems. We develop a simple analytical model for the delay dependence of the signal, which enables us to deduce the dephasing time from the four-wave mixing decay....
Local probing of magnetic films by optical excitation of magnetostatic waves
Chernov, A. I.; Kozhaev, M. A.; Vetoshko, P. M.; Dodonov, D. V.; Prokopov, A. R.; Shumilov, A. G.; Shaposhnikov, A. N.; Berzhanskii, V. N.; Zvezdin, A. K.; Belotelov, V. I.
2016-06-01
Excitation of volume and surface magnetostatic spin waves in ferrite garnet films by circularly polarized laser pulses utilizing to the inverse magnetooptical Faraday effect has been studied experimentally. The region of excitation of the magnetostatic spin waves is determined by the diameter of the laser beam (˜10 μm). At the same time, the characteristic propagation length of the modes is 30 μm. A method of finding the local characteristics of a magnetic film, in particular, the cubic and uniaxial anisotropy constants, based on the analysis of the azimuthal-angle dependence of the spectrum of the magnetostatic spin waves has been proposed.
Ueoka, Yoshiki; Slevin, Keith
2014-01-01
We report improved numerical estimates of the critical exponent of the Anderson transition in Anderson's model of localization in $d=4$ and $d=5$ dimensions. We also report a new Borel-Pad\\'e analysis of existing $\\epsilon$ expansion results that incorporates the asymptotic behaviour for $d\\to \\infty$ and gives better agreement with available numerical results.
Ćavar, Elizabeta; Blüm, Marie-Christine; Pivetta, Marina; Patthey, François; Chergui, Majed; Schneider, Wolf-Dieter
2005-01-01
Using the highly localized current of electrons tunneling through a double barrier Scanning Tunneling Microscope (STM) junction, we excite luminescence from a selected C$_{60}$ molecule in the surface layer of fullerene nanocrystals grown on an ultrathin NaCl film on Au(111). In the observed luminescence fluorescence and phosphorescence spectra, pure electronic as well as vibronically induced transitions of an individual C$_{60}$ molecule are identified, leading to unambiguous chemical recogn...
Conductance fluctuations in a macroscopic 3-dimensional Anderson insulator
We report magnetoconductance experiment on a amorphous Yx-Si1-x alloy (∼0.3). which is an Anderson insulator where spin-orbit scattering is strong. Two principal and new features emerge from the data: the first one is an halving of the localization length by the application of a magnetic field of about 2.5 Teslas. This effect is predicted by a new approach of transport in Anderson insulators where basic symetry considerations are the most important ingredient. The second one is the observation of reproducible conductance fluctuations at very low temperature in this macroscopic 3 D amorphous material
Thompson, Sally; Katul, Gabriel; Terborgh, John; Alvarez-Loayza, Patricia
2009-06-01
The Janzen-Connell (JC) effect, which hypothesizes that recruitment and growth of seedlings is positively correlated to the distance from the parent tree, is shown to generate highly organized vegetation biomass spatial patterns when coupled to a revised Fisher-Kolmogorov (FK) equation. Spatial organization arises through a novel mechanism of non-local activation and local inhibition. Over a single generation, the revised FK model calculations predict a “hen and chicks” dynamic pattern with mature trees surrounded by new seedlings growing at characteristic spatial distances in agreement with field data. Over longer timescales, the importance of stochastic dynamics, such as those associated with randomly occurring light gaps, increase thereby causing a substantial deviation between predictions from the deterministic FK model and its stochastic counterpart derived to account for such random disturbances. At still longer timescales, however, statistical measures of the spatial organization, specifically the spatial density of mature trees and their minimum spacing, converge between these two model representations.
An Anderson-like model of the QCD chiral transition
Giordano, Matteo; Pittler, Ferenc
2016-01-01
We study the problems of chiral symmetry breaking and eigenmode localisation in finite-temperature QCD by looking at the lattice Dirac operator as a random Hamiltonian. We recast the staggered Dirac operator into an unconventional three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying internal degrees of freedom, with disorder provided by the fluctuations of the gauge links. In this framework, we identify the features relevant to chiral symmetry restoration and localisation of the low-lying Dirac eigenmodes in the ordering of the local Polyakov lines, and in the related correlation between spatial links across time slices, thus tying the two phenomena to the deconfinement transition. We then build a toy model based on QCD and on the Dirac-Anderson approach, replacing the Polyakov lines with spin variables and simplifying the dynamics of the spatial gauge links, but preserving the above-mentioned relevant dynamical features. Our toy model successfully reproduces the main features of the...
Spin susceptibility of Anderson impurities in arbitrary conduction bands
Fang, Tie-Feng; Tong, Ning-Hua; Cao, Zhan; Sun, Qing-Feng; Luo, Hong-Gang
2015-10-01
Spin susceptibility of Anderson impurities is a key quantity in understanding the physics of Kondo screening. Traditional numerical renormalization group (NRG) calculation of the impurity contribution χimp to susceptibility, defined originally by Wilson in a flat wide band, has been generalized before to structured conduction bands. The results brought about non-Fermi-liquid and diamagnetic Kondo behaviors in χimp, even when the bands are not gapped at the Fermi energy. Here, we use the full density-matrix (FDM) NRG to present high-quality data for the local susceptibility χloc and to compare them with χimp obtained by the traditional NRG. Our results indicate that those exotic behaviors observed in χimp are unphysical. Instead, the low-energy excitations of the impurity in arbitrary bands only without gap at the Fermi energy are still a Fermi liquid and paramagnetic. We also demonstrate that unlike the traditional NRG yielding χloc less accurate than χimp, the FDM method allows a high-precision dynamical calculation of χloc at much reduced computational cost, with an accuracy at least one order higher than χimp. Moreover, artifacts in the FDM algorithm to χimp and origins of the spurious non-Fermi-liquid and diamagnetic features are clarified. Our work provides an efficient high-precision algorithm to calculate the spin susceptibility of impurity for arbitrary structured bands, while negating the applicability of Wilson's definition to such cases.
Ye, ChuanXiang [Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); Zhao, Yi, E-mail: yizhao@xmu.edu.cn, E-mail: liangwz@xmu.edu.cn [State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Liang, WanZhen, E-mail: yizhao@xmu.edu.cn, E-mail: liangwz@xmu.edu.cn [Department of Chemical Physics, University of Science and Technology of China, Hefei 230026 (China); State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China)
2015-10-21
The time-dependent correlation function approach for the calculations of absorption and resonance Raman spectra (RRS) of organic molecules absorbed on semiconductor surfaces [Y. Zhao and W. Z. Liang, J. Chem. Phys. 135, 044108 (2011)] is extended to include the contribution of the intermolecular charge transfer (CT) excitation from the absorbers to the semiconducting nanoparticles. The results demonstrate that the bidirectionally interfacial CT significantly modifies the spectral line shapes. Although the intermolecular CT excitation makes the absorption spectra red shift slightly, it essentially changes the relative intensities of mode-specific RRS and causes the oscillation behavior of surface enhanced Raman spectra with respect to interfacial electronic couplings. Furthermore, the constructive and destructive interferences of RRS from the localized molecular excitation and CT excitation are observed with respect to the electronic coupling and the bottom position of conductor band. The interferences are determined by both excitation pathways and bidirectionally interfacial CT.
The time-dependent correlation function approach for the calculations of absorption and resonance Raman spectra (RRS) of organic molecules absorbed on semiconductor surfaces [Y. Zhao and W. Z. Liang, J. Chem. Phys. 135, 044108 (2011)] is extended to include the contribution of the intermolecular charge transfer (CT) excitation from the absorbers to the semiconducting nanoparticles. The results demonstrate that the bidirectionally interfacial CT significantly modifies the spectral line shapes. Although the intermolecular CT excitation makes the absorption spectra red shift slightly, it essentially changes the relative intensities of mode-specific RRS and causes the oscillation behavior of surface enhanced Raman spectra with respect to interfacial electronic couplings. Furthermore, the constructive and destructive interferences of RRS from the localized molecular excitation and CT excitation are observed with respect to the electronic coupling and the bottom position of conductor band. The interferences are determined by both excitation pathways and bidirectionally interfacial CT
Thompson, S. E.; Katul, G. G.; Terborgh, J.; Alvarez-Loayza, P.
2009-12-01
Pattern formation in the biogeosciences is not limited to consideration of granular and fluid phenomena, but also occurs due to interactions within ecological systems. Here we present a novel mechanism of non-local activation and local inhibition that arises in the dynamics of competition and predation associated with parent trees and their seedlings. These dynamics, known as the Janzen-Connell (JC) effect, arise when recruitment and growth of seedlings is positively correlated to the distance from the parent tree. Such effects generate highly organized vegetation biomass spatial patterns when coupled to a revised Fisher-Kolmogorov (FK) equation. Over a single generation, the revised FK model calculations predict a "hen and chicks" dynamic pattern with mature trees surrounded by new seedlings growing at characteristic spatial distances in agreement with field data. Over longer timescales, the importance of stochastic dynamics, such as those associated with randomly occurring light gaps, increase thereby causing a substantial deviation between predictions from the deterministic FK model and its stochastic counterpart derived to account for such random disturbances. At still longer timescales, however, statistical measures of the spatial organization, specifically the spatial density of mature trees and their minimum spacing, converge between the two model representations.
Ultrahigh Enhancement of Electromagnetic Fields by Exciting Localized with Extended Surface Plasmons
Li, Anran; Abdulhalim, Ibrahim; Li, Shuzhou
2015-01-01
Excitation of localized surface plasmons (LSPs) of metal nanoparticles (NPs) residing on a flat metal film has attracted great attentions recently due to the enhanced electromagnetic (EM) fields found to be higher than the case of NPs on a dielectric substrate. In the present work, it is shown that even much higher enhancement of EM fields is obtained by exciting the LSPs through extended surface plasmons (ESPs) generated at the metallic film surface using the Kretschmann-Raether configuration. We show that the largest EM field enhancement and the highest surface-enhanced fluorescence intensity are obtained when the incidence angle is the ESP resonance angle of the underlying metal film. The finite-difference time-domain simulations indicate that excitation of LSPs using ESPs can generate 1-3 orders higher EM field intensity than direct excitation of the LSPs using incidence from free space. The ultrahigh enhancement is attributed to the strong confinement of the ESP waves in the vertical direction. The drast...
Stark effect of interfering electronic states: Localization of the nπ* excitations in toluquinone
Galaup, J. P.; Trommsdorff, H. P.
1984-04-01
High-precision Stark measurements on oriented single crystals of toluquinone at low temperatures have been performed and lead to an assessment of the electronic parenthood of the levels giving rise to the complex spectral region of interference between the two nearby nπ* excited states. The origin bands of the lowest excited singlet and triplet states are characterized by a measure of their factor-group splittings and an evaluation of the change in dipole moment and in polarizability upon excitation. The value of the change in dipole moment is shown to vary strongly between different vibrational levels of the lower state and an evaluation of the degree of localization of the electronic excitation on one CO group is made. The previous assignment of the second nπ* state is confirmed by the sign of the corresponding Stark shift. From measurements on crystals having been oriented in an electric field the absolute orientation of the polar crystal as well as the sign of the pyroelectric coefficient are proposed.
Regular and irregular patterns of self-localized excitation in arrays of coupled phase oscillators
Wolfrum, Matthias; Omel' chenko, Oleh E. [Weierstrass Institute, Mohrenstrasse 39, Berlin 10117 (Germany); Sieber, Jan [College of Engineering, Mathematics and Physical Sciences, University of Exeter, North Park Road, Exeter EX4 4QF (United Kingdom)
2015-05-15
We study a system of phase oscillators with nonlocal coupling in a ring that supports self-organized patterns of coherence and incoherence, called chimera states. Introducing a global feedback loop, connecting the phase lag to the order parameter, we can observe chimera states also for systems with a small number of oscillators. Numerical simulations show a huge variety of regular and irregular patterns composed of localized phase slipping events of single oscillators. Using methods of classical finite dimensional chaos and bifurcation theory, we can identify the emergence of chaotic chimera states as a result of transitions to chaos via period doubling cascades, torus breakup, and intermittency. We can explain the observed phenomena by a mechanism of self-modulated excitability in a discrete excitable medium.
Anderson Localization in the Induced Disorder System
Fei-Fei, Lu; Chun-Fang, Wang
2016-07-01
Not Available Supported by the National Natural Science Foundation of China under Grant Nos 11104185, 11174084 and 10934011, and the National Basic Research Program of China under Grant No 2012CB921904.
Excited states studied with density functional theory using local and non-local potentials
and for large-gap insulators. A better possibility is to adjust them individually to the studied systems. In this case the question remains to be solved how to determine the proper values of the parameters for a particular system. This question was investigated in the course of this thesis. Different properties were tested as starting point to determine the parameters automatically in a selfconsistent way. Another recently introduced approach is diagonal-only hybrid DFT which allows to obtain results of comparable quality in greatly reduced computation time. It was investigated how this approach can be combined with adjusting the parameters of the hybrid functional to the particular systems so that fast and correct calculations are possible. The TB-mBJ potential is based on the Becke-Johnson-potential which was proposed in 2006 and serves as an approximation to the exact exchange potential. Its speed is comparable to DFT calculations using standard functionals such as the local density approximation. This fact makes it an attractive alternative to more expensive approaches such as the above mentioned hybrid DFT. In this thesis its performance was studied for different classes of solids such as non-magnetic and (anti-)ferromagnetic semiconductors and metals. The resulting band gaps are compared to results from hybrid DFT and many-body perturbation theory. Furthermore the ability of TB-mBJ to predict other properties like magnetic moments or electric field gradients was investigated. The reasons behind cases where TB-mBJ works well and cases where it fails were analyzed as well. Based on the information gained by these investigations possible ways to further improvement were tested. (author)
Rasmussen, Kim; Christiansen, Peter Leth; Johansson, Magnus;
1998-01-01
with nearest-neighbor coupling we discuss the stability of highly localized, "breather-like", excitations under the influence of thermal fluctuations. Numerical analysis shows that the lifetime of the breather is aln,aps finite and in a large parameter region inversely proportional to the noise......A one-dimensional discrete nonlinear Schrodinger (DNLS) model with the power dependence, r(-s) on the distance r, of dispersive interactions is proposed. The stationary states of the system are studied both analytically and numerically. Two kinds of trial functions, exp-like and sech-like are...
The Anderson transition due to random spin-orbit coupling in two-dimension
Asada, Yoichi; Slevin, Keith; Ohtsuki, Tomi
2003-01-01
We report an analysis of the Anderson transition in an SU(2) model with chiral symmetry. Clear single parameter scaling behaviour is observed. We estimate the critical exponent for the divergence of the localization length to be $\
Ropers, C.
2007-07-11
This thesis contributes to the understanding of optical excitations in metallic nanostructures. In experiments on selected model structures, the dynamics of these excitations and their electromagnetic spatial modes are investigated with femtosecond temporal and nanometer spatial resolution, respectively. Angle- and time-resolved transmission experiments on metallic thin film gratings demonstrate the dominant role resonant surface plasmon polaritons (SPPs) play in the optical properties of such structures. The lifetimes of these excitations are determined, and it is shown that coherent couplings among SPP-resonances result in drastic lifetime modifications. Near the visible part of the spectrum, subradiant SPP lifetimes of up to 200 femtoseconds are observed, which is considerably longer than previously expected for these structures. The spatial SPP mode profiles are imaged using a custom-built near-field optical microscope. The experiments reveal a direct correlation between the spatial mode structure and the dynamics of different SPP resonances. Coupling-induced SPP band gaps are identified as splittings into symmetric and antisymmetric surface modes. These findings allow for an interpretation of the near-field optical image contrast in terms of the contributions of different vectorial components of the electromagnetic near-field. A selective imaging of different electric and magnetic field components is demonstrated for various types of near-field probes. Furthermore, the excitation of SPPs in periodic structures is employed in a novel type of near-field tip. The resonant excitation of SPPs in a nanofabricated grating on the shaft of a sharp metallic tip results in their concentration at the tip apex. The final part of the thesis highlights the importance of optical field enhancements for the local generation of nonlinear optical signals at the apex of sharp metallic tips. Specifically, the observation of intense multiphoton electron emission after femtosecond
Localization of bleomycin in a single living cell using three-photon excitation microscopy
Abraham, Anil T.; Brautigan, David L.; Hecht, Sidney M.; Periasamy, Ammasi
2001-04-01
Bleomycin has been used in the clinic as a chemotherapeutic agent for the treatment of several neoplasms, including non-Hodgkins lymphomas, squamous cell carcinomas, and testicular tumors. The effectiveness of bleomycin is believed to be derived from its ability to bind and oxidatively cleave DNA in the presence of a iron cofactor in vivo. A substantial amount of data on BLM has been collected, there is little information concerning the effects of bleomycin in living cells. In order to obtain data pertinent to the effects of BLM in intact cells, we have exploited the intrinsic fluorescence property of bleomycin to monitor the uptake of the drug in mammalian cells. We employed two light microscopy techniques, a wide-field and three-photon excitation (760 nm) fluorescence microscopy. Treatment of HeLa cells with bleomycin resulted in rapid to localization within the cells. In addition data collected from the wide field experiments, three-photon excitation of BLM which considerably reduced the phototoxic effect compared with UV light excitation in the wide-field microscopy indicated co-localization of the drug to regions of the cytoplasm occupied by the endoplasmic reticulum probe, DiOC5. The data clearly indicates that the cellular uptake of bleomycin after one minute includes the nucleus as well as in cytoplasm. Contrary to previous studies, which indicate chromosomal DNA as the target of bleomycin, the current findings suggest that the drug is distributed to many areas within the cell, including the endoplasmic reticulum, an organelle that is known to contain ribonucleic acids.
Baudin, Pablo; Kristensen, Kasper
2016-06-01
We present a local framework for the calculation of coupled cluster excitation energies of large molecules (LoFEx). The method utilizes time-dependent Hartree-Fock information about the transitions of interest through the concept of natural transition orbitals (NTOs). The NTOs are used in combination with localized occupied and virtual Hartree-Fock orbitals to generate a reduced excitation orbital space (XOS) specific to each transition where a standard coupled cluster calculation is carried out. Each XOS is optimized to ensure that the excitation energies are determined to a predefined precision. We apply LoFEx in combination with the RI-CC2 model to calculate the lowest excitation energies of a set of medium-sized organic molecules. The results demonstrate the black-box nature of the LoFEx approach and show that significant computational savings can be gained without affecting the accuracy of CC2 excitation energies.
An Anderson-like model of the QCD chiral transition
Giordano, Matteo; Kovács, Tamás G.; Pittler, Ferenc
2016-06-01
We study the problems of chiral symmetry breaking and eigenmode localisation in finite-temperature QCD by looking at the lattice Dirac operator as a random Hamiltonian. We recast the staggered Dirac operator into an unconventional three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying internal degrees of freedom, with disorder provided by the fluctuations of the gauge links. In this framework, we identify the features relevant to chiral symmetry restoration and localisation of the low-lying Dirac eigenmodes in the ordering of the local Polyakov lines, and in the related correlation between spatial links across time slices, thus tying the two phenomena to the deconfinement transition. We then build a toy model based on QCD and on the Dirac-Anderson approach, replacing the Polyakov lines with spin variables and simplifying the dynamics of the spatial gauge links, but preserving the above-mentioned relevant dynamical features. Our toy model successfully reproduces the main features of the QCD spectrum and of the Dirac eigenmodes concerning chiral symmetry breaking and localisation, both in the ordered (deconfined) and disordered (confined) phases. Moreover, it allows us to study separately the roles played in the two phenomena by the diagonal and the off-diagonal terms of the Dirac-Anderson Hamiltonian. Our results support our expectation that chiral symmetry restoration and localisation of the low modes are closely related, and that both are triggered by the deconfinement transition.
Evidence for Cation-Controlled Excited-State Localization in a Ruthenium Polypyridyl Compound.
Beauvilliers, Evan E; Meyer, Gerald J
2016-08-01
The visible absorption and photoluminescence (PL) properties of the four neutral ruthenium diimine compounds [Ru(bpy)2(dcb)] (B2B), [Ru(dtb)2(dcb)] (D2B), [Ru(bpy)2(dcbq)] (B2Q), and [Ru(dtb)2(dcbq)] (D2Q), where bpy is 2,2'-bipyridine, dcb is 4,4'-(CO2(-))2-bpy, dtb is 4,4'-(tert-butyl)2-bpy, and dcbq is 4,4'-(CO2(-))2-2,2'-biquinoline, are reported in the presence of Lewis acidic cations present in fluid solutions at room temperature. In methanol solutions, the measured spectra were insensitive to the presence of these cations, while in acetonitrile a significant red shift in the PL spectra (≤1400 cm(-1)) was observed consistent with stabilization of the metal-to-ligand charge transfer (MLCT) excited state through Lewis acid-base adduct formation. No significant spectral changes were observed in control experiments with the tetrabutylammonium cation. Titration data with Li(+), Na(+), Mg(2+), Ca(2+), Zn(2+), Al(3+), Y(3+), and La(3+) showed that the extent of stabilization saturated at high cation concentration with magnitudes that scaled roughly with the cation charge-to-size ratio. The visible absorption spectra of D2Q was particularly informative due to the presence of two well-resolved MLCT absorption bands: (1) Ru → bpy, λmax ≈ 450 nm; and (2) Ru → dcbq, λmax ≈ 540 nm. The higher-energy band blue-shifted and the lower-energy band red-shifted upon cation addition. The PL intensity and lifetime of the excited state of B2B first increased with cation addition without significant shifts in the measured spectra, behavior attributed to a cation-induced change in the localization of the emissive excited state from bpy to dcb. The importance of excited-state localization and stabilization for solar energy conversion is discussed. PMID:27391279
Quantum criticality at the Anderson transition: A typical medium theory perspective
Mahmoudian, Samiyeh; Tang, Shao; Dobrosavljević, Vladimir
2015-10-01
We present a complete analytical and numerical solution of the typical medium theory (TMT) for the Anderson metal-insulator transition. This approach self-consistently calculates the typical amplitude of the electronic wave functions, thus representing the conceptually simplest order-parameter theory for the Anderson transition. We identify all possible universality classes for the critical behavior, which can be found within such a mean-field approach. This provides insights into how interaction-induced renormalizations of the disorder potential may produce qualitative modifications of the critical behavior. We also formulate a simplified description of the leading critical behavior, thus obtaining an effective Landau theory for Anderson localization.
Self-Localized Quasi-Particle Excitation in Quantum Electrodynamics and Its Physical Interpretation
Feranchuk, Ilya D
2007-01-01
The self-localized quasi-particle excitation of the electron-positron field (EPF) is found for the first time in the framework of a standard form of the quantum electrodynamics. This state is interpreted as the ``physical'' electron (positron) and it allows one to solve the following problems: i) to express the ``primary'' charge $e_0$ and the mass $m_0$ of the ``bare'' electron in terms of the observed values of $e$ and $m$ of the ``physical'' electron without any infinite parameters and by essentially nonperturbative way; ii) to consider $\\mu$-meson as another self-localized EPF state and to estimate the ratio $m_{\\mu}/m$; iii) to prove that the self-localized state is Lorentz-invariant and its energy spectrum corresponds to the relativistic free particle with the observed mass $m$; iv) to show that the expansion in a power of the observed charge $e \\ll 1$ corresponds to the strong coupling expansion in a power of the ``primary'' charge $e^{-1}_0 \\sim e $ when the interaction between the ``physical'' electr...
Self-Localized Quasi-Particle Excitation in Quantum Electrodynamics and Its Physical Interpretation
Feranchuk, Ilya D.; Feranchuk, Sergey I.
2007-12-01
The self-localized quasi-particle excitation of the electron-positron field (EPF) is found for the first time in the framework of a standard form of the quantum electrodynamics. This state is interpreted as the ''physical'' electron (positron) and it allows one to solve the following problems: i) to express the ''primary'' charge e0 and the mass m0 of the ''bare'' electron in terms of the observed values of e and m of the ''physical'' electron without any infinite parameters and by essentially nonperturbative way; ii) to consider μ-meson as another self-localized EPF state and to estimate the ratio mμ/m; iii) to prove that the self-localized state is Lorentz-invariant and its energy spectrum corresponds to the relativistic free particle with the observed mass m; iv) to show that the expansion in a power of the observed charge e << 1 corresponds to the strong coupling e! xpansion in a power of the ''primary'' charge e-10 ~ e when the interaction between the ``physical'' electron and the transverse electromagnetic field is considered by means of the perturbation theory and all terms of this series are free from the ultraviolet divergence.
Self-Localized Quasi-Particle Excitation in Quantum Electrodynamics and Its Physical Interpretation
Ilya D. Feranchuk
2007-12-01
Full Text Available The self-localized quasi-particle excitation of the electron-positron field (EPF is found for the first time in the framework of a standard form of the quantum electrodynamics. This state is interpreted as the ''physical'' electron (positron and it allows one to solve the following problems: i to express the ''primary'' charge $e_0$ and the mass $m_0$ of the ''bare'' electron in terms of the observed values of $e$ and $m$ of the ''physical'' electron without any infinite parameters and by essentially nonperturbative way; ii to consider $mu$-meson as another self-localized EPF state and to estimate the ratio $m_mu/m$; iii to prove that the self-localized state is Lorentz-invariant and its energy spectrum corresponds to the relativistic free particle with the observed mass $m$; iv to show that the expansion in a power of the observed charge $e ll 1$ corresponds to the strong coupling expansion in a power of the ''primary'' charge $e^{-1}_0 sim e$ when the interaction between the ''physical'' electron and the transverse electromagnetic field is considered by means of the perturbation theory and all terms of this series are free from the ultraviolet divergence.
Localization of scalar massless excitations in self-gravitating $SO(10)$ kinks
Chavez, Rafael; Rodriguez, R Omar
2016-01-01
Three self-gravitating $SO(10)$ kinks inducing asymptotically the breaking pattern $SO(10)\\rightarrow SU(5)$ are determined which can be distinguished by the unbroken group on each of them: $SO(10)$ for the first kink and $SO(6)\\times SU(2)\\times U(1)$ and $SU(4)\\times SO(2)\\times U(1)$ for the second and third kink respectively. The scenarios are perturbed by considering small excitations on the fields; in particular, the metric fluctuations are parameterized in terms of tensor, vector and scalar modes. All these modes as well as the perturbations of the scalar field are rewritten as gauge-invariant variables. With regarding the tensor and vector fluctuations, for a four dimensional observer, the standard results are obtained: while the massless graviton is localized on the wall the graviphotons propagate freely in the bulk. On the other hand, for the scalar excitations in correspondence with the symmetry on the kink, both along the broken generators and along the some unbroken generators, normalizable zero ...
Fletcher, Patrick; Bertram, Richard; Tabak, Joel
2016-06-01
Models of electrical activity in excitable cells involve nonlinear interactions between many ionic currents. Changing parameters in these models can produce a variety of activity patterns with sometimes unexpected effects. Further more, introducing new currents will have different effects depending on the initial parameter set. In this study we combined global sampling of parameter space and local analysis of representative parameter sets in a pituitary cell model to understand the effects of adding K (+) conductances, which mediate some effects of hormone action on these cells. Global sampling ensured that the effects of introducing K (+) conductances were captured across a wide variety of contexts of model parameters. For each type of K (+) conductance we determined the types of behavioral transition that it evoked. Some transitions were counterintuitive, and may have been missed without the use of global sampling. In general, the wide range of transitions that occurred when the same current was applied to the model cell at different locations in parameter space highlight the challenge of making accurate model predictions in light of cell-to-cell heterogeneity. Finally, we used bifurcation analysis and fast/slow analysis to investigate why specific transitions occur in representative individual models. This approach relies on the use of a graphics processing unit (GPU) to quickly map parameter space to model behavior and identify parameter sets for further analysis. Acceleration with modern low-cost GPUs is particularly well suited to exploring the moderate-sized (5-20) parameter spaces of excitable cell and signaling models. PMID:27033230
Benedict Andersons forestillede fællesskaber
Ivarsson, Søren
2007-01-01
Artiklen diskuterer Benedict Andersons analyse af nationalismens opståen i en kolonial kontekst og den kritik som Partha Chatterjee har rejst mod denne. Udgivelsesdato: Januar 2008......Artiklen diskuterer Benedict Andersons analyse af nationalismens opståen i en kolonial kontekst og den kritik som Partha Chatterjee har rejst mod denne. Udgivelsesdato: Januar 2008...
Excitation of XPS spectra from nanoscaled particles by local generation of x-rays
In preliminary work, the authors have shown that use of an aluminum substrate to support a distribution of copper particles enables their characteristic photoelectrons to be observed within the Auger electron spectrum generated by an incident electron beam. This observation raises the possibility of the use of chemical shifts and the corresponding Auger parameter to identify the chemical states present on the surface of individual submicrometer particles within a mixture. In this context, the technique has an advantage in that, unlike conventional Auger electron spectroscopy, the electron beam does not dwell on the particle but on the substrate adjacent to it. Given the importance, for both medical and toxicological reasons, of the surface composition of such particles, the authors have continued to explore the potential of this development. In this contribution, the authors show that proximal excitation of x-rays is equally successful with magnesium substrates. In some regions of the x-ray photoelectron spectrum, the much larger Auger peaks generated by the electron beam can cause inconvenient clustering of Auger and photoelectron peaks. As in conventional x-ray photoelectron spectroscopy, the ability to switch between Al and Mg sources is useful in such situations. In this context, the authors have extended the studies to iron particles where the authors show that use of Al or Mg substrates, as necessary, can make a contribution to clear identification of individual components in the Fe 2p peaks. For this development in electron spectroscopy to achieve its full potential, it is necessary to optimize the beam conditions used to generate the local x-ray to give good selectivity of a given particle. Measurements made in support of this will be given. Of greater concern is a possible problem of local heating associated with x-ray generation. The authors continue to explore this problem and report some progress in minimizing heating of the particle while maintaining
Critical parameters from generalised multifractal analysis at the Anderson transition
Rodriguez, Alberto; Vasquez, Louella J.; Slevin, Keith; Römer, Rudolf A.
2010-01-01
We propose a generalization of multifractal analysis that is applicable to the critical regime of the Anderson localization-delocalization transition. The approach reveals that the behavior of the probability distribution of wavefunction amplitudes is sufficient to characterize the transition. In combination with finite-size scaling, this formalism permits the critical parameters to be estimated without the need for conductance or other transport measurements. Applying this method to high-pre...
Fermi-liquid theory for the single-impurity Anderson model
Mora, Christophe; Moca, Cǎtǎlin Paşcu; von Delft, Jan; Zaránd, Gergely
2015-08-01
We generalize Nozières' Fermi-liquid theory for the low-energy behavior of the Kondo model to that of the single-impurity Anderson model. In addition to the electrons' phase shift at the Fermi energy, the low-energy Fermi-liquid theory is characterized by four Fermi-liquid parameters: the two given by Nozières that enter to first order in the excitation energy, and two additional ones that enter to second order and are needed away from particle-hole symmetry. We express all four parameters in terms of zero-temperature physical observables, namely the local charge and spin susceptibilities and their derivatives with respect to the local level position. We determine these in terms of the bare parameters of the Anderson model using Bethe ansatz and numerical renormalization group (NRG) calculations. Our low-energy Fermi-liquid theory applies throughout the crossover from the strong-coupling Kondo regime via the mixed-valence regime to the empty-orbital regime. From the Fermi-liquid theory, we determine the conductance through a quantum dot symmetrically coupled to two leads in the regime of small magnetic field, low temperature, and small bias voltage, and compute the coefficients of the ˜B2 , ˜T2 , and ˜V2 terms exactly in terms of the Fermi-liquid parameters. The coefficients of T2, V2, and B2 are found to change sign during the Kondo to empty-orbital crossover. The crossover becomes universal in the limit that the local interaction is much larger than the level width. For completeness, we also compute the shot noise and discuss the resulting Fano factor.
Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening
Kamimura, H. A. S.; Wang, S.; Wu, S.-Y.; Karakatsani, M. E.; Acosta, C.; Carneiro, A. A. O.; Konofagou, E. E.
2015-10-01
Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n = 15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5-1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were 9.38+/- 5.71 mm3, 8.91+/- 3.91 mm3and 35.47+/- 5.10 mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were 55.40+/- 28.43 V.s, 63.87+/- 29.97 V.s and 356.52+/- 257.15 V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue.
Superconductivity in Anderson lattice model
We study the superconducting instabilities generated by the inclusion in the Anderson lattice model of a density-density attractive potential between correlated electrons on nearest-neighbouring sites. Using a description of the normal phase based on a perturbative expansion around the atomic limit, we treat the attractive potential in the broken symmetry Hartree-Fock scheme and analyze which of the possible symmetries of the superconducting order parameter leads to the highest possible transition temperature in the case of a two-dimensional square lattice. For values of the on-site f-repulsion large compared to the hopping amplitude, a suppression of any possible superconducting phase occurs, regardless of the of the symmetry of the order parameter. (author)
Nembrini, Nicola; Peli, Simone; Banfi, Francesco; Ferrini, Gabriele; Singh, Yogesh; Gegenwart, Philipp; Comin, Riccardo; Foyevtsova, Kateryna; Damascelli, Andrea; Avella, Adolfo; Giannetti, Claudio
2016-01-01
We use time- and energy-resolved optical spectroscopy to investigate the coupling of electron-hole excitations to the local magnetic environment in the relativistic Mott insulator Na$_2$IrO$_3$. We show that, on the picosecond timescale, the photoinjected electron-hole pairs delocalize on the hexagons of the Ir lattice forming quasi-molecular orbital (QMO) excitations and exchanging energy with the short-range ordered magnetic background. Our results provide a unifying picture of the physics ...
Price-Anderson Law - reports on Price-Anderson issues
Five of the six papers in this study are by experts outside the nuclear industry, and deal with fear, risk, and risk management as they apply to the review of the Price-Anderson Act. The purpose of the Act is to encourage private enterprise to develop a reliable source of electric power and to protect the public from the financial consequences of injury or damage that may occur during the process. The titles of the five papers are: (1) the effects of ionizing radiation on human health, (2) proof of causation through expert opinion evidence in low-level radiation cases, (3) a critical review of the probability of causation method, (4) the nuclear liability claims experience of the nuclear insurance pools, (5) review of nuclear liability compensation systems applicable to reactors outside the United States, and (6) the economic foundations of limited liability for nuclear reactor accidents. A separate abstract was prepared for each of the papers for EDB, EPA, and INS
Topological approximation of the nonlinear Anderson model
Milovanov, Alexander V.; Iomin, Alexander
2014-06-01
We study the phenomena of Anderson localization in the presence of nonlinear interaction on a lattice. A class of nonlinear Schrödinger models with arbitrary power nonlinearity is analyzed. We conceive the various regimes of behavior, depending on the topology of resonance overlap in phase space, ranging from a fully developed chaos involving Lévy flights to pseudochaotic dynamics at the onset of delocalization. It is demonstrated that the quadratic nonlinearity plays a dynamically very distinguished role in that it is the only type of power nonlinearity permitting an abrupt localization-delocalization transition with unlimited spreading already at the delocalization border. We describe this localization-delocalization transition as a percolation transition on the infinite Cayley tree (Bethe lattice). It is found in the vicinity of the criticality that the spreading of the wave field is subdiffusive in the limit t →+∞. The second moment of the associated probability distribution grows with time as a power law ∝ tα, with the exponent α =1/3 exactly. Also we find for superquadratic nonlinearity that the analog pseudochaotic regime at the edge of chaos is self-controlling in that it has feedback on the topology of the structure on which the transport processes concentrate. Then the system automatically (without tuning of parameters) develops its percolation point. We classify this type of behavior in terms of self-organized criticality dynamics in Hilbert space. For subquadratic nonlinearities, the behavior is shown to be sensitive to the details of definition of the nonlinear term. A transport model is proposed based on modified nonlinearity, using the idea of "stripes" propagating the wave process to large distances. Theoretical investigations, presented here, are the basis for consistency analysis of the different localization-delocalization patterns in systems with many coupled degrees of freedom in association with the asymptotic properties of the
Tunable local excitation of surface plasmon polaritons by sum-frequency generation in ZnO nanowires
Brincker, Mads; Pedersen, Kjeld; Skovsen, Esben
2015-12-01
Tunable local excitation of surface plasmon polaritons (SPP) by sum-frequency generation (SFG) in Zinc Oxide (ZnO) nanowires on a smooth and thin silver film has been studied by applying angle resolved leakage radiation spectroscopy. SFG between an infrared (IR) source, with a variable wavelength in the telecom range between 1350 nm and 1550 nm, and a near-infrared (NIR) source with a fixed wavelength of 790 nm resulted in the excitation of SPP's at wavelengths between 498 nm and 523 nm. The SFG to SPP coupling efficiency was studied as a function of the excitation angle and the wavelength of the IR source. It was shown that the SPP coupling was most efficient at oblique excitation angles, and that SFG in ZnO nanowires allows for the coherent conversion of optical signals at telecom frequencies to SPP's with frequencies within the visible range.
Student trainee report of Walter L. Anderson
US Fish and Wildlife Service, Department of the Interior — The following report is intended to summarize the activities of Walter L. Anderson, Student Trainee (Wildlife Biology) at Malheur National Wildlife Refuge during...
Germinet, François
2011-01-01
We consider the discrete Anderson model and prove enhanced Wegner and Minami estimates where the interval length is replaced by the IDS computed on the interval. We use these estimates to improve on the description of finite volume eigenvalues and eigenfunctions obtained in a previous paper. As a consequence of the improved description of eigenvalues and eigenfunctions, we revisit a number of results on the spectral statistics in the localized regime and extend their domain of validity, namely : - the local spectral statistics for the unfolded eigenvalues; - the local asymptotic ergodicity of the unfolded eigenvalues; In dimension 1, for the standard Anderson model, the improvement enables us to obtain the local spectral statistics at band edge, that is in the Lifshitz tail regime. In higher dimensions, this works for modified Anderson models.
My Random Walks in Anderson's Garden
Baskaran, G
2016-01-01
Anderson's Garden is a drawing presented to Philip W. Anderson on the eve of his 60th birthday celebration, in 1983. This cartoon (Fig. 1), whose author is unknown, succinctly depicts some of Anderson's pre-1983 works, as a blooming garden. As an avid reader of Anderson's papers, random walk in Anderson's garden had become a part of my routine since graduate school days. This was of immense help and prepared me for a wonderful collaboration with the gardener himself, on the resonating valence bond (RVB) theory of High Tc cuprates and quantum spin liquids, at Princeton. The result was bountiful - the first (RVB mean field) theory for i) quantum spin liquids, ii) emergent fermi surfaces in Mott insulators and iii) superconductivity in doped Mott insulators. Beyond mean field theory - i) emergent gauge fields, ii) Ginzbuerg Landau theory with RVB gauge fields, iii) prediction of superconducting dome, iv) an early identification and study of a non-fermi liquid normal state of cuprates and so on. Here I narrate th...
QIANG Ji-Ye; FEI Jin-Xi; CAI Gui-Ping; ZHENG Chun-Long
2007-01-01
With the aid of an improved projective approach and a linear variable separation method,new types of variable separation solutions (including solitary wave solutions,periodic wave solutions,and rational function solutions)with arbitrary functions for (2+1)-dimensional Korteweg-de Vries system are derived.Usually,in terms of solitary wave solutions and rational function solutions,one can find some important localized excitations.However,based on the derived periodic wave solution in this paper,we find that some novel and significant localized coherent excitations such as dromions,peakons,stochastic fractal patterns,regular fractal patterns,chaotic line soliton patterns as well as chaotic patterns exist in the KdV system as considering appropriate boundary conditions and/or initial qualifications.
Zitian Li
2014-09-01
A broad general variable separation solution with two arbitrary lower-dimensional functions of the (2+1)-dimensional Broer–Kaup (BK) equations was derived by means of a projective equation method and a variable separation hypothesis. Based on the derived variable separation excitation, some new special types of localized solutions such as oscillating solitons, instantonlike and cross-like fractal structures are revealed by selecting appropriate functions of the general variable separation solution.
An extension of the Local-Scale Transformation Method (LSTM) by inclusion of N scalar functions is suggested. An application of LSTM to the Hartree-Fock theory is considered. By means of the suggested approach an investigation of the 'breathing' monopole excitation mode within the Adiabatic limit of the Time-Dependent Hartree-Fock Theory (ATDHF) is carried out. Numeric results in a particular case of pure scale transformation using the Skyrme forces for the nucleus 16O are obtained
The energy of the atom electron system is a functional of the local-scale function. The minimal value of this functional is greatest lower band of the atom energy in certain class wave functions. This class has obtained after a local-scale point transformation of the chosen model wave function which is not varied. A slater determinant with excited electron states is chosen in this survey as a model wave function. After the local scaling of this wave function the atom energy of corresponding state becomes the functional of the local scale transformation function. The minimization of this functional gives to the atom some energy corresponding to the considered state. LSTM also allows to obtain one-particle energy of the electron in excited state. In contrast to the Hartree-Fock method in the offered approach the variation over all one-particle orbitals is replaced by the variation over only one function. The case of variation over more than one local scale transformation function is also presented. (author)
Describing excited state relaxation and localization in TiO2 nanoparticles using TD-DFT
We have investigated the description of excited state relaxation in naked and hydrated TiO2 nanoparticles using Time-Dependent Density Functional Theory (TD-DFT) with three common hybrid exchange-correlation (XC) potentials; B3LYP, CAM-B3LYP and BHLYP. Use of TD-CAM-B3LYP and TD-BHLYP yields qualitatively similar results for all structures, which are also consistent with predictions of coupled cluster theory for small particles. TD-B3LYP, in contrast, is found to make rather different predictions; including apparent conical intersections for certain particles that are not observed with TD-CAM-B3LYP nor with TD-BHLYP. In line with our previous observations for vertical excitations, the issue with TD-B3LYP appears to be the inherent tendency of TD-B3LYP, and other XC potentials with no or a low percentage of Hartree-Fock Like Exchange, to spuriously stabilize the energy of charge-transfer (CT) states. Even in the case of hydrated particles, for which vertical excitations are generally well described with all XC potentials, the use of TD-B3LYP appears to result in CT-problems for certain particles. We hypothesize that the spurious stabilization of CT-states by TD-B3LYP even may drive the excited state optimizations to different excited state geometries than those obtained using TD-CAM-B3LYP or TD-BHLYP. In conclusion, focusing on the TD-CAM-B3LYP and TD-BHLYP results, excited state relaxation in naked and hydrated TiO2 nanoparticles is predicted to be associated with a large Stokes' shift
Localization phenomena in interacting Rydberg lattice gases with position disorder
Marcuzzi, Matteo; Barredo, Daniel; de Léséleuc, Sylvain; Labuhn, Henning; Lahaye, Thierry; Browaeys, Antoine; Levi, Emanuele; Lesanovsky, Igor
2016-01-01
Disordered systems provide paradigmatic instances of ergodicity breaking and localization phenomena. Here we explore the dynamics of excitations in a system of Rydberg atoms held in optical tweezers. The finite temperature produces an intrinsic uncertainty in the atomic positions, which translates into quenched correlated disorder in the interatomic interaction strengths. In a simple approach, the dynamics in the many-body Hilbert space can be understood in terms of a one-dimensional Anderson-like model with disorder on every other site, featuring both localized and delocalized states. We conduct an experiment on an eight-atom chain and observe a clear suppression of excitation transfer. Our experiment accesses a regime which is described by a two-dimensional Anderson model on a "trimmed" square lattice. Our results thus provide a concrete example in which the absence of excitation propagation in a many-body system is directly related to Anderson-like localization in the Hilbert space, which is believed to be...
Excitation of localized modes and mechanism of random lasing forming in random media
WANG Hong; LIU Jinsong; WANG Kejia; HAN Yanling
2006-01-01
Laser phenomena in random media have been studied based on the localized theory for lightwave in random media. The relationship between random lasing modes and localized modes has been investigated by directly solving Maxwell equations numerically via the finite difference time domain method. The spatial distribution and the spectra of localized modes are obtained for both passive and active random media. The results show that random lasing modes directly originate from the localized modes inside the random medium. In the presence of gain, any one of the localized modes can be amplified and can serve as random lasing mode.
Topology dependent quantities at the Anderson transition
Slevin, Keith; Ohtsuki, Tomi; Kawarabayashi, Tohru
2000-01-01
The boundary condition dependence of the critical behavior for the three dimensional Anderson transition is investigated. A strong dependence of the scaling function and the critical conductance distribution on the boundary conditions is found, while the critical disorder and critical exponent are found to be independent of the boundary conditions.
Corrections to scaling at the Anderson transition
Slevin, Keith; Ohtsuki, Tomi
1998-01-01
We report a numerical analysis of corrections to finite size scaling at the Anderson transition due to irrelevant scaling variables and non-linearities of the scaling variables. By taking proper account of these corrections, the universality of the critical exponent for the orthogonal universality class for three different distributions of the random potential is convincingly demonstrated.
Huber, A J; Ocelic, N; Hillenbrand, R
2008-03-01
We demonstrate that mid-infrared surface phonon polariton excitation, propagation and interference can be studied by scattering-type near-field optical microscopy (s-SNOM). In our experiments we image surface phonon polaritons (SPPs) propagating on flat SiC crystals. They are excited by weakly focused illumination of single or closely spaced metal disks we fabricated on the SiC surface by conventional photolithography. SPP imaging is performed by pseudo-heterodyne interferometric detection of infrared light scattered by the metal tip of our s-SNOM. The pseudo-heterodyne technique simultaneously yields optical amplitude and phase images which allows us to measure the SPP wave vector--including its sign--and the propagation length and further to study SPP interference. High resolution imaging of SPPs could be applied to investigate for example SPP focusing or heat transfer by SPPs in low dimensional nanostructures. PMID:18331484
Exact finite volume expectation values of local operators in excited states
Pozsgay, B; Takacs, G
2014-01-01
We present a conjecture for the exact expression of finite volume expectation values in excited states in integrable quantum field theories, which is an extension of an earlier conjecture to the case of general diagonal factorized scattering with bound states and a nontrivial bootstrap structure. The conjectured expression is a spectral expansion which uses the exact form factors and the excited state thermodynamic Bethe Ansatz as building blocks. The conjecture is proven for the case of the trace of the energy-moment tensor. Concerning its validity for more general operators, we provide numerical evidence using the truncated conformal space approach. It is found that the expansion fails to be well-defined for small values of the volume in cases when the singularity structure of the TBA equations undergoes a non-trivial rearrangement under some critical value of the volume. Despite these shortcomings, the conjectured expression is expected to be valid for all volumes for most of the excited states, and as an ...
He, Hao; Chan, Kam Tai; Kong, Siu Kai; Lee, Rebecca Kit Ying
2009-12-01
We examined the effect of femtosecond (fs) and continuous wave (CW) lasers at near-infrared range on the creation of reactive oxygen species in a human liver cancer cell line. By controlling the mitochondria electron transport chain (ETC), it was found that a major part of the oxidative stress was generated by the laser induced thermal effect on the mitochondria while the remaining part was created by direct free electron liberation by the fs pulses, which could be observed after breaking the ETC. The study helps clarify the major effects produced on animal cells when excited by fs lasers.
Spatial dispersion effects upon local excitation of extrinsic plasmons in a graphene micro-disk
Mencarelli, D.; Bellucci, S.; Sindona, A.; Pierantoni, L.
2015-11-01
Excitation of surface plasmon waves in extrinsic graphene is studied using a full-wave electromagnetic field solver as analysis engine. Particular emphasis is placed on the role played by spatial dispersion due to the finite size of the two-dimensional material at the micro-scale. A simple instructive set up is considered where the near field of a wire antenna is held at sub-micrometric distance from a disk-shaped graphene patch. The key-input of the simulation is the graphene conductivity tensor at terahertz frequencies, being modeled by the Boltzmann transport equation for the valence and conduction electrons at the Dirac points (where a linear wave-vector dependence of the band energies is assumed). The conductivity equation is worked out in different levels of approximations, based on the relaxation time ansatz with an additional constraint for particle number conservation. Both drift and diffusion currents are shown to significantly contribute to the spatially dispersive anisotropic features of micro-scale graphene. More generally, spatial dispersion effects are predicted to influence not only plasmon propagation free of external sources, but also typical scanning probe microscopy configurations. The paper sets the focus on plasmon excitation phenomena induced by near field probes, being a central issue for the design of optical devices and photonic circuits.
Fidler, Andrew F.; Singh, Ved P.; Long, Phillip D.; Dahlberg, Peter D.; Engel, Gregory S.
2014-02-01
Time-resolved ultrafast optical probes of chiral dynamics provide a new window allowing us to explore how interactions with such structured environments drive electronic dynamics. Incorporating optical activity into time-resolved spectroscopies has proven challenging because of the small signal and large achiral background. Here we demonstrate that two-dimensional electronic spectroscopy can be adapted to detect chiral signals and that these signals reveal how excitations delocalize and contract following excitation. We dynamically probe the evolution of chiral electronic structure in the light-harvesting complex 2 of purple bacteria following photoexcitation by creating a chiral two-dimensional mapping. The dynamics of the chiral two-dimensional signal directly reports on changes in the degree of delocalization of the excitonic states following photoexcitation. The mechanism of energy transfer in this system may enhance transfer probability because of the coherent coupling among chromophores while suppressing fluorescence that arises from populating delocalized states. This generally applicable spectroscopy will provide an incisive tool to probe ultrafast transient molecular fluctuations that are obscured in non-chiral experiments.
The Interplay between Localized and Propagating Plasmonic Excitations Tracked in Space and Time
Lemke, Christoph; Leißner, Till; Evlyukhin, Andrey;
2014-01-01
In this work, the mutual coupling and coherent interaction of propagating and localized surface plasmons within a model-type plasmonic assembly is experimentally demonstrated, imaged, and analyzed. Using interferometric time-resolved photoemission electron microscopy the interplay between...... ultrashort surface plasmon polariton wave packets and plasmonic nanoantennas is monitored on subfemtosecond time scales. The data reveal real-time insights into dispersion and localization of electromagnetic fields as governed by the elementary modes determining the functionality of plasmonic operation units....
Controlling Spiral Dynamics in Excitable Media by a Weakly Localized Pacing
LI Bing-Wei; SUN Li-Li; CHEN Bin; YING He-Ping
2007-01-01
@@ Spiral dynamics controlled by a weakly localized pacing around the spiral tip is investigated. Numerical simulations show two distinct characteristics when the pacing is applied with the weak amplitude for suitable frequencies:for a rigidly rotating spiral, a transition from rigid rotation to meandering motion is observed, and for unstable spiral waves, spiral breakup can be prevented. Successfully preventing spiral breakup is relevant to the modulation of the tip trajectory induced by a localized pacing.
Some Ergodic Theorems for a Parabolic Anderson Model
Yong LIU; Feng Xia YANG
2012-01-01
In this paper,we study some ergodic theorems of a class of linear systems of interacting diffusions,which is a parabolic Anderson model.First,under the assumption that the transition kernel a =(a(i,j))i,j∈s is doubly stochastic,we obtain the long-time convergence to an invariant probability measure Vh starting from a bounded a-harmonic function h based on self-duality property,and then we show the convergence to the invariant probability measure vh holds for a broad class of initial distributions.Second,if (a(i,j))i,j∈s is transient and symmetric,and the diffusion parameter c remains below a threshold,we are able to determine the set of extremal invariant probability measures with finite second moment.Finally,in the case that the transition kernel (a(i,j))i,j∈s is doubly stochastic and satisfies Case Ⅰ (see Case Ⅰ in [Shiga,T.:An interacting system in population genetics.J.Math.Kyoto Univ.,20,213-242 (1980)]),we show that this parabolic Anderson model locally dies out independent of the diffusion parameter c.
Chiral Condensate and Mott-Anderson Freeze-Out
We present the idea of a Mott-Anderson freeze-out that suggests a key role of the localization of the hadron wave functions when traversing the hadronization transition. The extension of hadron wave functions in dense matter is governed by the behavior of the chiral quark condensate such that its melting at finite temperatures and chemical potentials entails an increase of the size of hadrons and thus their geometrical strong interaction cross sections. It is demonstrated within a schematic resonance gas model, that a kinetic freeze-out condition reveals a correlation with the reduction of the chiral condensate in the phase diagram up to 50% of its vacuum value. Generalizing the description of the chiral condensate by taking into account a full hadron resonance gas such correlation gets distorted. We discuss, that this may be due to our approximations in calculating the chiral condensate which disregard both, in-medium effects on hadron masses and hadron-hadron interactions. The latter, in particular due to quark exchange reactions, could lead to a delocalization of the hadron wave functions in accordance with the picture of a Mott-Anderson transition. (author)
Anderson introduces a new biomass baler
D' amour, L.; Lavoie, F. [Anderson Group Co., Chesterville, PQ (Canada)
2010-07-01
Canadian-based Anderson Group Company has developed an innovative round baler for harvesting a large variety of woody biomass. The baler was initially developed in 2005 in collaboration with the University Laval and Agriculture and Agri-Food Canada. The third generation BIOBALER{sup TM} is currently built, engineered and commercialized by Anderson. It can produce up to 40 bales/hr in short rotations woody crops such as willow and hybrid poplar. The unit can harvest brushes up to 125 mm in diameter. A standard tractor can pull the BIOBALER in fallow or abandoned land, under power transmission lines, and between planted trees. The patented BIOBALER includes a mulcher head attachment, a choice of long or short swivel tongue, a fixed chamber and an undercarriage frame.
Integrative Medicine Program- MD Anderson Cancer Center
Lee, Richard T.
2012-01-01
The Integrative Medicine Program at MD Anderson Cancer Center was first established in 1998. Our mission is to empower patients with cancer and their families to become active partners in their own physical, psycho-spiritual, and social health through personalized education and evidenced-based clinical care to optimize health, quality of life, and clinical outcomes across the cancer continuum. The program consists of three main components: clinical care, research, and education. The Integr...
López-González, Dany; Molina, Mario I.
2016-03-01
We examine the transport of extended and localized excitations in one-dimensional linear chains populated by linear and nonlinear symmetric identical n -mers (with n =3 , 4, 5, and 6), randomly distributed. First, we examine the transmission of plane waves across a single linear n -mer, paying attention to its resonances, and looking for parameters that allow resonances to merge. Within this parameter regime we examine the transmission of plane waves through a disordered and nonlinear segment composed by n -mers randomly placed inside a linear chain. It is observed that nonlinearity tends to inhibit the transmission, which decays as a power law at long segment lengths. This behavior still holds when the n -mer parameters do not obey the resonance condition. On the other hand, the mean square displacement exponent of an initially localized excitation does not depend on nonlinearity at long propagation distances z , and shows a superdiffusive behavior ˜z1.8 for all n -mers, when parameters obey the resonance merging condition; otherwise the exponent reverts back to the random dimer model value ˜z1.5 .
Collective excitations of dipolar gases based on local tunneling in ultracold superlattices
Cao, L; Deng, X; Schmelcher, P
2016-01-01
The collective dynamics of a dipolar fermionic quantum gas confined in a one-dimensional double-well superlattice is explored. The fermionic gas resides in a paramagnetic-like ground state in the weak interaction regime, upon which a new type of collective dynamics is found when applying a local perturbation. This dynamics is composed of the local tunneling of fermions in separate supercells, and is a pure quantum effect, with no classical counterpart. Due to the presence of the dipolar interactions the local tunneling transports through the entire superlattice, giving rise to a collective dynamics. A well-defined momentum-energy dispersion relation is identified in the ab-initio simulations demonstrating the phonon-like behavior. The phonon-like characteristic is also confirmed by an analytical description of the dynamics within a semiclassical picture.
Alguire, Ethan C; Fatehi, Shervin; Shao, Yihan; Subotnik, Joseph E
2014-12-26
In a previous paper [ Fatehi , S. ; et al. J. Chem. Phys. 2013 , 139 , 124112 ], we demonstrated a practical method by which analytic derivative couplings of Boys-localized CIS states can be obtained. In this paper, we now apply that same method to the analysis of triplet-triplet energy transfer systems studied by Closs and collaborators [ Closs , G. L. ; et al. J. Am. Chem. Soc. 1988 , 110 , 2652 ]. For the systems examined, we are able to conclude that (i) the derivative coupling in the BoysOV basis is negligible, and (ii) the diabatic coupling will likely change little over the configuration space explored at room temperature. Furthermore, we propose and evaluate an approximation that allows for the inexpensive calculation of accurate diabatic energy gradients, called the "strictly diabatic" approximation. This work highlights the effectiveness of diabatic state analytic gradient theory in realistic systems and demonstrates that localized diabatic states can serve as an acceptable approximation to strictly diabatic states. PMID:24447246
Krah, Tim; Ben Amor, Nadia; Maynau, Daniel; Berger, J A; Robert, Vincent
2014-07-01
Based on localized molecular orbitals, the proposed method reduces large configuration interaction (CI) spaces while maintaining agreement with reference values. Our strategy concentrates the numerical effort on physically pertinent CI-contributions and is to be considered as a tool to tackle large systems including numerous open-shells. To show the efficiency of our method we consider two 4-electron parent systems. First, we illustrate our approach by describing the van der Waals interactions in the (H2)2 system. By systematically including local correlation, dispersion and charge transfer mechanisms, we show that 90% of the reference full CI dissociation energy of the H2 dimer is reproduced using only 3% of the full CI space. Second, the conformational cis/trans rotation barrier of the butadiene molecule is remarkably reproduced (97% of the reference value) with less than 1% of the reference space. This work paves the way to numerical strategies which afford the electronic structure determination of large open-shell systems avoiding the exponential limitation. At the same time, a physical analysis of the contents of the wave function is offered. PMID:24935105
Lifshitz transitions in magnetic phases of the periodic Anderson model
We investigate the reconstruction of a Fermi surface, which is called a Lifshitz transition, in magnetically ordered phases of the periodic Anderson model on a square lattice with a finite Coulomb interaction between f electrons. We apply the variational Monte Carlo method to the model by using the Gutzwiller wavefunctions for the paramagnetic, antiferromagnetic, ferromagnetic, and charge-density-wave states. We find that an antiferromagnetic phase is realized around half-filling and a ferromagnetic phase is realized when the system is far away from half-filling. In both magnetic phases, Lifshitz transitions take place. By analyzing the electronic states, we conclude that the Lifshitz transitions to large ordered-moment states can be regarded as itinerant-localized transitions of the f electrons. (author)
Unconstitutionality of Section 170 (e) of the price Anderson Act
Several environmental protection groups in the State of North Carolina have recently contested the conformity with the United States Constitution of Section 170 (e) of the Atomic Energy Act (Price-Anderson Act). The court seized of the question (the United States District Court for the western district of North Carolina, Charlotte Division) held in March 1977 that this Section and the other provisions of the Atomic Energy Act concerning implementation of the $560 million limitation of liability for nuclear damage were unconstitutional and unenforceable insofar as they applied to nuclear incidents occurring inside the United States. The defendants, the former United States Atomic Energy Commission and its then Commissioners as well as the Duke Power Company (the local electricity company) will appeal this decision. The note on case law analyses the arguments retained by the court. (NEA)
Rasmussen, K. Ø.; Christiansen, P. L.; Johansson, M.; Gaididei, Yu. B.; Mingaleev, S. F.
1998-03-01
A one-dimensional discrete nonlinear Schrödinger (DNLS) model with the power dependence, r- s on the distance r, of dispersive interactions is proposed. The stationary states of the system are studied both analytically and numerically. Two kinds of trial functions, exp-like and sech-like are exploited and the results of both approaches are compared. Both on-site and inter-site stationary states are investigated. It is shown that for s sufficiently large all features of the model are qualitatively the same as in the DNLS model with nearest-neighbor interaction. For s less than some critical value, scr, there is an interval of bistability where two stable stationary states exist at each excitation number. The bistability of on-site solitons may occur for dipole-dipole dispersive interaction ( s = 3), while scr for inter-site solitions is close to 2.1. In the framework of the DNLS equation with nearest-neighbor coupling we discuss the stability of highly localized, “breather-like”, excitations under the influence of thermal fluctuations. Numerical analysis shows that the lifetime of the breather is always finite and in a large parameter region inversely proportional to the noise variance for fixed damping and nonlinearity. We also find that the decay rate of the breather decreases with increasing nonlinearity and with increasing damping.
Powell, B J
2015-01-01
There is longstanding fundamental interest in 6-fold coordinated d(6) (t(2g)(6)) transition metal complexes such as [Ru(bpy)3](2+) and Ir(ppy)3, particularly their phosphorescence. This interest has increased with the growing realisation that many of these complexes have potential uses in applications including photovoltaics, imaging, sensing, and light-emitting diodes. In order to design new complexes with properties tailored for specific applications a detailed understanding of the low-energy excited states, particularly the lowest energy triplet state, T1, is required. Here we describe a model of pseudo-octahedral complexes based on a pseudo-angular momentum representation and show that the predictions of this model are in excellent agreement with experiment - even when the deviations from octahedral symmetry are large. This model gives a natural explanation of zero-field splitting of T1 and of the relative radiative rates of the three sublevels in terms of the conservation of time-reversal parity and total angular momentum modulo two. We show that the broad parameter regime consistent with the experimental data implies significant localization of the excited state. PMID:26123864
Gokhale, Shreyas; Hima Nagamanasa, K.; Sood, A. K.; Ganapathy, Rajesh
2016-07-01
Elucidating the nature of the glass transition has been the holy grail of condensed matter physics and statistical mechanics for several decades. A phenomenological aspect that makes glass formation a conceptually formidable problem is that structural and dynamic correlations in glass-forming liquids are too subtle to be captured at the level of conventional two-point functions. As a consequence, a host of theoretical techniques, such as quenched amorphous configurations of particles, have been devised and employed in simulations and colloid experiments to gain insights into the mechanisms responsible for these elusive correlations. Very often, though, the analysis of spatio-temporal correlations is performed in the context of a single theoretical framework, and critical comparisons of microscopic predictions of competing theories are thereby lacking. Here, we address this issue by analysing the distribution of localized excitations, which are building blocks of relaxation as per the dynamical facilitation (DF) theory, in the presence of an amorphous wall, a construct motivated by the random first-order transition theory (RFOT). We observe that spatial profiles of the concentration of excitations exhibit complex features such as non-monotonicity and oscillations. Moreover, the smoothly varying part of the concentration profile yields a length scale {ξc} , which we compare with a previously computed length scale {ξ\\text{dyn}} . Our results suggest a method to assess the role of dynamical facilitation in governing structural relaxation in glass-forming liquids.
Near-field optical microscopy of localized excitations on rough surfaces: influence of a probe
Bozhevolnyi, Sergey I.
1999-01-01
calculate the self consistent field intensity at the site of a probe dipole scanning over resonantly interacting object dipoles and show that the intensity distribution deviates from that existing in the absence of a probe. I demonstrate that this difference increases with an increase in the polarizability...... of the probe dipole, resulting eventually in a completely different intensity distribution, The calculations also show that the perturbation of the intensity distribution due to the presence of a probe decreases with an increase in the probe-sample distance. In order to evaluate the degree of...... perturbation, I suggest comparing the images obtained at different probe-sample distances, Finally I formulate a simple rule of thumb that allows one to roughly estimate the probe-sample coupling when imaging localized elicitations....
Vattikonda, Anirudh; Surampudi, Bapi Raju; Banerjee, Arpan; Deco, Gustavo; Roy, Dipanjan
2016-08-01
Computational modeling of the spontaneous dynamics over the whole brain provides critical insight into the spatiotemporal organization of brain dynamics at multiple resolutions and their alteration to changes in brain structure (e.g. in diseased states, aging, across individuals). Recent experimental evidence further suggests that the adverse effect of lesions is visible on spontaneous dynamics characterized by changes in resting state functional connectivity and its graph theoretical properties (e.g. modularity). These changes originate from altered neural dynamics in individual brain areas that are otherwise poised towards a homeostatic equilibrium to maintain a stable excitatory and inhibitory activity. In this work, we employ a homeostatic inhibitory mechanism, balancing excitation and inhibition in the local brain areas of the entire cortex under neurological impairments like lesions to understand global functional recovery (across brain networks and individuals). Previous computational and empirical studies have demonstrated that the resting state functional connectivity varies primarily due to the location and specific topological characteristics of the lesion. We show that local homeostatic balance provides a functional recovery by re-establishing excitation-inhibition balance in all areas that are affected by lesion. We systematically compare the extent of recovery in the primary hub areas (e.g. default mode network (DMN), medial temporal lobe, medial prefrontal cortex) as well as other sensory areas like primary motor area, supplementary motor area, fronto-parietal and temporo-parietal networks. Our findings suggest that stability and richness similar to the normal brain dynamics at rest are achievable by re-establishment of balance. PMID:27177761
Integrative Medicine Program- MD Anderson Cancer Center
Richard T Lee
2012-06-01
Full Text Available The Integrative Medicine Program at MD Anderson Cancer Center was first established in 1998. Our mission is to empower patients with cancer and their families to become active partners in their own physical, psycho-spiritual, and social health through personalized education and evidenced-based clinical care to optimize health, quality of life, and clinical outcomes across the cancer continuum. The program consists of three main components: clinical care, research, and education. The Integrative Medicine Center provides clinical services to patients through individual and group programs. The clinical philosophy of the center is to work collaboratively with the oncology teams to build comprehensive and integrative care plans that are personalized, evidence-based, and safe with the goal of improving clinical outcomes. The individual services comprise of integrative oncology consultation, acupuncture, meditation, music therapy, nutrition, and oncology massage. The center also provides a variety of group programs including meditation, yoga, tai chi, cooking classes and others. Over the past 13 years, over 70,000 patients and families have participated in services and programs offered by the center. The research portfolio focuses on three main areas: mind-body interventions, acupuncture, and meditation. This lecture will focus on providing an overview of the Integrative Medicine Program at MD Anderson with a focus on the clinical services provided. Participants will learn about the integrative clinical model and how this is applied to the care of cancer patients at MD Anderson Cancer Center. Current and future research topics will be discussed as well as patient cases.
Evaluating the Anderson-Darling Distribution
George Marsaglia
2004-02-01
Full Text Available Except for n = 1, only the limit as n approaches infinity for the distribution of the Anderson-Darling test for uniformity has been found, and that in so complicated a form that published values for a few percentiles had to be determined by numerical integration, saddlepoint or other approximation methods. We give here our method for evaluating that asymptotic distribution to great accuracy--directly, via series with two-term recursions. We also give, for any particular n, a procedure for evaluating the distribution to the fourth digit, based on empirical CDF's from samples of size 1010 .
High pressure luminescence studies of localized excitations in ZnS doped with Pb2+ and Mn2+
High pressure luminescence measurements have been made on ZnS doped with Pb+2 and Mn+2. The data include changes in peak energy and shape, integrated intensities, and lifetimes. These localized emissions are treated in terms of a single configuration coordinate model. For Pb+2 the emission peak shifted to lower energy by a moderate amount and narrowed. For excitation in the Pb+2 absorption the intensity was independent of pressure, which is consistent with the fact that the energy barrier for radiationless return to the ground state was high at all pressures. For excitation in the ZnS absorption edge the intensity decreased significantly with pressure above about 80 kbar. Data on shifts of the conduction band with pressure would indicate that one is approaching a transition from a direct to indirect transition at high pressure so that decrease in emission intensity may be associated with decreased absorption efficiency. The Mn+2 emission peak shifted strongly to lower energy with increasing pressure. The direction and magnitude of the shift were consistent with the predictions of ligand field theory. The intensity doubled in 100 kbar, while the lifetime decreased by roughly a factor of 2. These results could be described in terms of a model for a phonon assisted transition. In addition, peak location, intensity, and lifetime measurements were made on ZnS:Pb:Mn. There is clear evidence of energy transfer by exchange, but in addition there is a nonradiative process in the doubly doped crystal which affects both intensities and lifetimes
Anderson transition in the three dimensional symplectic universality class
Asada, Yoichi; Slevin, Keith; Ohtsuki, Tomi
2004-01-01
We study the Anderson transition in the SU(2) model and the Ando model. We report a new precise estimate of the critical exponent for the symplectic universality class of the Anderson transition. We also report numerical estimation of the $\\beta$ function.
Perturbation theory for Lyapunov exponents of an Anderson model on a strip
Schulz-Baldes, H
2003-01-01
It is proven that the localization length of an Anderson model on a strip of width $L$ is bounded above by $L/\\lambda^2$ for small values of the coupling constant $\\lambda$ of the disordered potential. For this purpose, a new formalism is developed in order to calculate the bottom Lyapunov exponent associated with random products of large symplectic matrices perturbatively in the coupling constant of the randomness.
Determinant method and quantum simulations of many-body effects in a single impurity Anderson model
We present a short description of a quantum Monte Carlo technique that has proved useful for simulating many-body effects in systems of interacting fermins at finite temperatures. We then report our preliminary results using this technique on a single impurity Anderson model. Examples of such many-body effects as local moment formation, Kondo behavior, and mixed valence phenomena found in the simulations are shown
Determinant method and quantum simulations of many-body effects in a single impurity Anderson model
A short description is presented of a quantum Monte Carlo technique, often referred to as the determinant method, that has proved useful for simulating many-body effects in systems of interacting fermions at finite temperatures. Preliminary results using this technique on a single impurity Anderson model are reported. Examples of such many-body effects as local moment formation, Kondo behavior, and mixed valence phenomena found in the simulations are shown. 10 refs., 3 figs
Plea for European Price Anderson legislation
The paper analyses the essential features and the basic differences in nuclear liability and coverage in the United States where the problem is governed by the Price-Anderson legislation, and the Member States of the European Community which adhere to the Paris Convention on Third Party Liability in the Field of Nuclear Energy. The paper undertakes to show that it is possible to introduce into the European Community certain elements of the American regime, in particular the solidarity of nuclear operators and the retroactive premium coverage without violating the basic principles of the Paris Convention. Consequently the paper advocates the adoption of such rules in Europe as a step towards harmonisation of nuclear coverage and safety and a means to reduce government interference. (author)
Slow Relaxation in Anderson Critical Systems
Choi, Soonwon; Yao, Norman; Choi, Joonhee; Kucsko, Georg; Lukin, Mikhail
2016-05-01
We study the single particle dynamics in disordered systems with long range hopping, focusing on the critical cases, i.e., the hopping amplitude decays as 1 /rd in d-dimension. We show that with strong on-site potential disorder, the return probability of the particle decays as power-law in time. As on-site potential disorder decreases, the temporal profile smoothly changes from a simple power-law to the sum of multiple power-laws with exponents ranged from 0 to νmax. We analytically compute the decay exponents using a simple resonance counting argument, which quantitatively agrees with exact numerical results. Our result implies that the dynamics in Anderson Critical systems are dominated by resonances. Harvard-MIT CUA, Kwanjeong Educational Fellowship, AFOSR MURI, Samsung Scholarship.
Anderson Exploration Ltd. 1998 annual report
In 1998, Anderson Exploration's undeveloped land inventory in the western provinces decreased 7% to 3,183,000 net acres largely due to lease expiries and drilling activity. The undeveloped land base is located 63% in Alberta, 19% in British Columbia, 17% in Saskatchewan, and 1% in Manitoba. During 1998, Anderson Exploration participated in drilling 446 wells for oil and gas vs. 669 for 1997. The average working interest in the wells was 63% vs. 64% in 1997. In 1998, the company spent $109 million on the construction of field gathering systems and production facilities vs. $123 million in 1997. In 1998, the company's gas sales increased to 555 million cubic feet per day from 549 million cubic feet per day in 1997. Crude oil sales averaged 29,808 barrels per day in 1998, an increase of 9% over the 1997 production. In 1998, the company replaced 148% of production with proven reserve additions, net of revisions, by spending 163% of cash flow from operations on capital spending. After a volatile year in 1 997, natural gas prices stabilized somewhat in 1998. A modest price increase was experienced in 1997. The company's average plant gate natural gas price increased modestly in 1998 to $1.94 per thousand cubic feet, marking the 3rd consecutive price increase. The company owns an average interest of 10.4% in two straddle plants at Empress, Alberta. The company operates and is a 50% owner of Federated Pipe Lines Ltd. The company is committed to protecting the health and safety of all employees and the public, as well as preserving the quality of the environment
Feng, Lei; Yi, Xiaohua; Zhu, Dapeng; Xie, Xiongyao; Wang, Yang
2015-08-01
In a modern metropolis, metro rail systems have become a dominant mode for mass transportation. The structural health of a metro tunnel is closely related to public safety. Many vibration-based techniques for detecting and locating structural damage have been developed in the past several decades. However, most damage detection techniques and validation tests are focused on bridge and building structures; very few studies have been reported on tunnel structures. Among these techniques, transmissibility function and cross correlation analysis are two well-known diagnostic approaches. The former operates in frequency domain and the latter in time domain. Both approaches can be applied to detect and locate damage through acceleration data obtained from sensor arrays. Furthermore, the two approaches can directly utilize structural response data without requiring excitation measurement, which offers advantages in field testing on a large structure. In this research, a numerical finite element model of a metro tunnel is built and different types of structural defects are introduced at multiple locations of the tunnel. Transmissibility function and cross correlation analysis are applied to perform structural damage detection and localization, based on simulated structural vibration data. Numerical results demonstrate that the introduced defects can be successfully identified and located. The sensitivity and feasibility of the two approaches have been verified when sufficient distribution of measurement locations is available. Damage detection results of the two different approaches are compared and discussed.
钟卫平; Milivoj R. Belic; HUANG Ting-Wen
2012-01-01
We report on the localized spatial soliton excitations in the multidimensional nonlinear Schrodinger equation with radially variable nonlinearity coefficient and an external potential. By using Hirota＇s binary differential operators, we determine a variety of external potentials and nonlinearity coefficients that can support nonlinear localized solutions of different but desired forms. For some specific external potentials and nonlinearity coefficients, we discuss features of the corresponding （2＋1）-dimensional multisolitonic solutions, including ring solitons, lump solitons, and soliton clusters.
Critical exponent for the Anderson transition in the three-dimensional orthogonal universality class
We report a careful finite size scaling study of the metal–insulator transition in Anderson's model of localization. We focus on the estimation of the critical exponent ν that describes the divergence of the localization length. We verify the universality of this critical exponent for three different distributions of the random potential: box, normal and Cauchy. Our results for the critical exponent are consistent with the measured values obtained in experiments on the dynamical localization transition in the quantum kicked rotor realized in a cold atomic gas. (paper)
Magnetic field induced quantum phase transitions in the two-impurity Anderson model
Zhu, Lujun [Los Alamos National Laboratory; Zhu, Jian - Xin [Los Alamos National Laboratory
2010-11-17
In the two-impurity Anderson model, the inter-impurity spin exchange interaction favors a spin singlet state between two impurities leading to the localization of quasiparticles. We show that a local uniform magnetic field can delocalize the quasiparticies to restore the Kondo resonance. This transition is found to be continuous, accompanied by not only the divergence of the staggered (anti ferromagnetic) susceptibility, but also the divergence of the uniform spin susceptibility. This implies that the magnetic field induced quantum phase transitions in Kondo systems are in favor of the local critical type.
Transverse Anderson Localization in Disordered Glass Optical Fibers: A Review
Arash Mafi; Salman Karbasi; Koch, Karl W.; Thomas Hawkins; John Ballato
2014-01-01
Disordered optical fibers show novel waveguiding properties that can be used for various device applications, such as beam-multiplexed optical communications and endoscopic image transport. The strong transverse scattering from the transversely disordered optical fibers results in transversely confined beams that can freely propagate in the longitudinal direction, similar to conventional optical fibers, with the advantage that any point in the cross section of the fiber can be used for beam t...
Zheng Chun-Long; Fang Jian-Ping; Chen Li-Qun
2005-01-01
By means of an extended mapping approach, a new type of variable-separation excitation is derived with two arbitrary functions in a (2+1)-dimensional modified dispersive water-wave system. Based on the derived variable-separation excitation, abundant nonpropagating and propagating solitons such as dromions, rings, peakons and compactons are revealed by selecting appropriate functions in this paper.
Numerical verification of universality for the Anderson transition
Slevin, Keith; Ohtsuki, Tomi
2001-01-01
We analyze the scaling behavior of the higher Lyapunov exponents at the Anderson transition. We estimate the critical exponent and verify its universality and that of the critical conductance distribution for box, Gaussian and Lorentzian distributions of the random potential.
Martin Anderson valis "Joonase lähetamise" / Priit Kuusk
Kuusk, Priit, 1938-
2000-01-01
M. Anderson kommenteeris ameerika muusikaajakirjas "Fanfare" viit talle kõige enam mõju avaldanud heliplaati, sh. R. Tobiase oratooriumi "Joonase lähetamine" CD-plaati (BIS). M. Andersoni huvist eesti muusika vastu
2011 South Carolina DNR Lidar: Tricounty (Anderson, Oconee, Pickens)
National Oceanic and Atmospheric Administration, Department of Commerce — Towill Inc. collected LiDAR for over 3,500 square miles in York, Pickens, Anderson, and Oconee Counties in South Carolina. The nominal pulse spacing for this...
Scaling of the conductance distribution near the Anderson transition
Slevin, Keith; Markoš, Peter; Ohtsuki, Tomi
2002-01-01
The single parameter scaling hypothesis is the foundation of our understanding of the Anderson transition. However, the conductance of a disordered system is a fluctuating quantity which does not obey a one parameter scaling law. It is essential to investigate the scaling of the full conductance distribution to establish the scaling hypothesis. We present a clear cut numerical demonstration that the conductance distribution indeed obeys one parameter scaling near the Anderson transition.
Finite Size Scaling Analysis of the Anderson Transition
Kramer, Bernhard; MacKinnon, Angus; Ohtsuki, Tomi; Slevin, Keith
2010-01-01
This chapter describes the progress made during the past three decades in the finite size scaling analysis of the critical phenomena of the Anderson transition. The scaling theory of localisation and the Anderson model of localisation are briefly sketched. The finite size scaling method is described. Recent results for the critical exponents of the different symmetry classes are summarised. The importance of corrections to scaling are emphasised. A comparison with experiment is made, and a di...
The Anderson transition: time reversal symmetry and universality
Slevin, Keith; Ohtsuki, Tomi
1997-01-01
We report a finite size scaling study of the Anderson transition. Different scaling functions and different values for the critical exponent have been found, consistent with the existence of the orthogonal and unitary universality classes which occur in the field theory description of the transition. The critical conductance distribution at the Anderson transition has also been investigated and different distributions for the orthogonal and unitary classes obtained.
Ferromagnetic order in the one-dimensional Anderson lattice
Using bosonization an effective Hamiltonian is derived for the one-dimensional Anderson lattice model in the Toulouse limit. The effective Hamiltonian exhibits ferromagnetic ground state in the intermediate coupling regime. - Highlights: • 1D Anderson lattice is bosonized in the Toulouse limit. • The obtained effective Hamiltonian exhibits ferromagnetic order. • Ferromagnetism is due to a double-exchange mechanism. • The ferromagnetic transition has been identified to be an order–disorder transition
Many-body localization: Entanglement and efficient numerical simulations
Pollmann, Frank
Many-body localization (MBL) occurs in isolated quantum systems when Anderson localization persists in the presence of finite interactions. To understand this phenomenon, the development of new efficient numerical methods to find highly excited many-body eigenstates is essential. In this talk, we will discuss two complimentary approaches to simulate MBL systems: First, we introduce a variant of the density-matrix renormalization group (DMRG) method that obtains individual highly excited eigenstates of MBL systems to machine precision accuracy at moderate to large disorder. This method explicitly takes advantage of the local spatial structure and the low entanglement which is characteristic for MBL eigenstates. Second, we propose an approach to directly find an approximate compact representation of the diagonalizing unitary by using a variational unitary matrix-product operator.
Anderson metal-insulator transitions with classical magnetic impurities
Jung, Daniel; Kettemann, Stefan; Slevin, Keith
2016-04-01
We study numerically the effects of classical magnetic impurities on the Anderson metal-insulator transition. We find that a small concentration of Heisenberg impurities enhances the critical disorder amplitude Wc with increasing exchange coupling strength J . The resulting scaling with J is analyzed which supports an anomalous scaling prediction by Wegner due to the combined breaking of time-reversal and spin-rotational symmetry. Moreover, we find that the presence of magnetic impurities lowers the critical correlation length exponent ν and enhances the multifractality parameter α0. The new value of ν improves the agreement with the value measured in experiments on the metal-insulator transition (MIT) in doped semiconductors like phosphor-doped silicon, where a finite density of magnetic moments is known to exist in the vicinity of the MIT. The results are obtained by a finite-size scaling analysis of the geometric mean of the local density of states which is calculated by means of the kernel polynomial method. We establish this combination of numerical techniques as a method to obtain critical properties of disordered systems quantitatively.
Soh, Wee Tee, E-mail: a0046479@u.nus.edu; Ong, C. K. [Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); Peng, Bin [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)
2015-04-21
We demonstrate the localized excitation and dc electrical detection of magnetostatic surface spin waves (MSSWs) in yttrium iron garnet (YIG) by a shorted coaxial probe. Thin films of NiFe and Pt are patterned at different regions onto a common bulk YIG substrate. A shorted coaxial probe is used to excite spin precession locally near various patterned regions. The dc voltages across the corresponding regions are recorded. For excitation of the Pt regions, the dc voltage spectra are dominated by the spin pumping of MSSWs from YIG, where various modes can be clearly distinguished. For the NiFe region, it is also found that spin pumping from MSSWs generated in YIG dominated the spectra, indicating that the spin pumped currents are dissipated into charge currents via the inverse Spin Hall effect (ISHE) in NiFe. For all regions, dc signals from YIG MSSWs are observed to be much stronger than the ferromagnetic resonance (FMR) uniform mode, likely due to the nature of the microwave excitation. The results indicate the potential of this probe for microwave imaging via dc detection of spin dynamics in continuous and patterned films.
Investigation of Anderson lattice behavior in Yb1-xLuxAl3
Measurements of magnetic susceptibility χ(T), specific heat C(T), Hall coefficient RH(T), and Yb valence ν = 2 + nf [f-occupation number nf (T) determined from Yb L3 x-ray absorption measurements] were carried out on single crystals of Yb1-xLuxAl3. The low temperature anomalies observed in χ(T) and C(T) corresponding to an energy scale Tcoh ∼ 40 K in the intermediate valence, Kondo lattice compound YbAl3 are suppressed by Lu concentrations as small as 5% suggesting these low-T anomalies are extremely sensitive to disorder and, therefore, are a true coherence effect. By comparing the temperature dependence of various physical quantities to the predictions of the Anderson Impurity Model, the slow crossover behavior observed in YbAl3, in which the data evolve from a low-temperature coherent, Fermi-liquid regime to a high temperature local moment regime more gradually than predicted by the Anderson Impurity Model, appears to evolve to fast crossover behavior at x ∼ 0.7 where the evolution is more rapid than predicted. These two phenomena found in Yb1-xLuxAl3, i.e., the low-T anomalies and the slow/fast crossover behavior are discussed in relation to recent theories of the Anderson lattice
The extended local-scale transformation method (LSTM) in combination with the natural orbital representation is applied to investigate the nuclear ground state local density and momentum distributions. The 'breathing' monopole excitation mode is considered within this approach and the adiabatic limit of the time-dependent Hartree-Fock theory (ATDHF). Numeric calculations for the nucleus 16O with the effective Skyrme forces have been carried out. The occupation numbers are determined, taking into account the experimantal charge density distribution data. 2 figs., 1 tab., 13 refs
Superdiffusive transport and energy localization in disordered granular crystals
Martínez, Alejandro J.; Kevrekidis, P. G.; Porter, Mason A.
2016-02-01
We study the spreading of initially localized excitations in one-dimensional disordered granular crystals. We thereby investigate localization phenomena in strongly nonlinear systems, which we demonstrate to differ fundamentally from localization in linear and weakly nonlinear systems. We conduct a thorough comparison of wave dynamics in chains with three different types of disorder—an uncorrelated (Anderson-like) disorder and two types of correlated disorders (which are produced by random dimer arrangements)—and for two types of initial conditions (displacement excitations and velocity excitations). We find for strongly precompressed (i.e., weakly nonlinear) chains that the dynamics depend strongly on the type of initial condition. In particular, for displacement excitations, the long-time asymptotic behavior of the second moment m˜2 of the energy has oscillations that depend on the type of disorder, with a complex trend that differs markedly from a power law and which is particularly evident for an Anderson-like disorder. By contrast, for velocity excitations, we find that a standard scaling m˜2˜tγ (for some constant γ ) applies for all three types of disorder. For weakly precompressed (i.e., strongly nonlinear) chains, m˜2 and the inverse participation ratio P-1 satisfy scaling relations m˜2˜tγ and P-1˜t-η , and the dynamics is superdiffusive for all of the cases that we consider. Additionally, when precompression is strong, the inverse participation ratio decreases slowly (with η disorder, and the dynamics leads to a partial localization around the core and the leading edge of a propagating wave packet. For an Anderson-like disorder, displacement perturbations lead to localization of energy primarily in the core, and velocity perturbations cause the energy to be divided between the core and the leading edge. This localization phenomenon does not occur in the sonic-vacuum regime, which yields the surprising result that the energy is no longer