Observation of intermolecular double-quantum coherence signal dips in nuclear magnetic resonance
Institute of Scientific and Technical Information of China (English)
Shen Gui-Ping; Cai Cong-Bo; Cai Shu-Hui; Chen Zhong
2011-01-01
The correlated spectroscopy revamped by asymmetric Z-gradient echo detection (CRAZED) sequence is modified to investigate intermolecular double-quantum coherence nuclear magnetic resonance signal dips in highly polarized spin systems.It is found that the occurrence of intermolecular double-quantum coherence signal dips is related to sample geometry,field inhomogeneity and dipolar correlation distance.If the field inhomogeneity is refocused,the signal dip occurs at a fixed position whenever the dipolar correlation distance approaches the sample dimension.However,the position is shifted when the field inhomogeneity exists.Experiments and simulations are performed to validate our theoretic analysis.These signal features may offer a unique way to investigate porous structures and may find applications in biomedicine and material science.
Institute of Scientific and Technical Information of China (English)
Shen Gui-Ping; Cai Cong-Bo; Cai Shu-Hui; Chen Zhong
2009-01-01
A modified correlated spectroscopy (COSY) revamped with asymmetric Z-gradient echo detection sequence was designed to investigate the influence of diffusion behaviour on intermolecular double-quantum coherence signal attenuation during the pre-acquisition period. Theoretical formulas were deduced and experimental measurements and simulations were performed. It is found that the diffusion behaviour of intermolecular double-quantum coherence in the pre-acquisition period may be different from that of conventional single-quantum coherence, depending on the relative orientation of diffusion weighting gradients to coherence selection gradients. When the orientation of the diffusion weighting gradients is parallel or anti-parallel to the orientation of the coherence selection gradients, the diffusion is modulated by the distant dipolar field. This study is helpful for understanding the signal properties in intermolecular double-quantum coherence magnetic resonance imaging.
Wang, Chuchu; Zhang, Liandi; Wei, Zhiliang; Lin, Liangjie; Lin, Yanqin; Chen, Zhong
2015-04-01
High-resolution nuclear magnetic resonance spectroscopy is widely used to analyze molecular structures and compositions. Here, we present a pulse sequence that simultaneously detects both intermolecular zero- (iZQC) and double-quantum coherence (iDQC) signals in inhomogeneous fields, offering high-resolution spectra in absolute-value mode after data processing. In comparison with pure iZQC or iDQC spectra, the proposed sequence can provide nearly doubled spectral resolutions and suppressions of strong coupling artifacts. It is the first time that iZQC and iDQC signals can be simultaneously obtained in one single measurement. This sequence may provide an alternative approach to studies of in situ inhomogeneous chemical systems.
Heteronuclear intermolecular single-quantum coherences in liquid nuclear magnetic resonance
Institute of Scientific and Technical Information of China (English)
Chen Song; Zhu Xiao-Qin; Cai Shu-Hui; Chen Zhong
2008-01-01
This paper analyses the heteronuclear Cosy Revamped by Asymmetric Z-gradient Echo Detection pulse sequence.General theoretical expressions of the pulse sequence with arbitrary flip angles were derived by using dipolar field treatment and signals originating from heteronuclear intermolecular single-quantum coherences (iSQCs) in highly-polarized two spin-1/2 systems were mainly discussed in order to find the optimal flip angles.The results show that signals from heteronuclear iSQCs decay slower than those from intermolecular double-quantum coherences or intermolecular zero-quantum coherences. Magical angle experiments validate that the signals are from heteronuclear iSQCs and insensitive to the imperfection of radio-frequency flip angles. All experimental observations are in excellent agreement with theoretical predictions. The quantum-mechanical treatment leads to similar predictions to the dipolar field treatment.
Bonneau, Philippe
Following a preceding paper showing how the introduction of a t.v.s. topology on quantum groups led to a remarkable unification and rigidification of the different definitions, we adapt here, in the same way, the definition of quantum double. This topological double is dualizable and reflexive (even for infinite dimensional algebras). In a simple case we show, considering the double as the "zero class" of an extension theory, the uniqueness of the double structure as a quasi-Hopf algebra. A la suite d'un précédent article montrant comment l'introduction d'une topologie d'e.v.t. sur les groupes quantiques permet une unification et une rigidification remarquables des différentes définitions, on adapte ici de la même manière la définition du double quantique. Ce double topologique est alors dualisable et reflexif (même pour des algèbres de dimension infinie). Dans un cas simple on montre, en considérant le double comme la "classe zéro" d'une théorie d'extensions, l'unicité de cette structure comme algèbre quasi-Hopf.
Directory of Open Access Journals (Sweden)
Daijiro Fukuda
2004-01-01
Full Text Available Using diagrammatic pictures of tensor contractions, we consider a Hopf algebra (Aop⊗ℛλA** twisted by an element ℛλ∈A*⊗Aop corresponding to a Hopf algebra morphism λ:A→A. We show that this Hopf algebra is quasitriangular with the universal R-matrix coming from ℛλ when λ2=idA, generalizing the quantum double construction which corresponds to the case λ=idA.
Colloidal Double Quantum Dots.
Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan
2016-05-17
Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
@@ Pursuit of new contrast in imaging has been the driving force behind many innovative applications of physics in medical MRI. Even though the use of intramolecular multiple quantum coherence in NMR spectroscopy has a long history, intermolecular multiple quantum coherence (iMQC) among spins on different molecules, such as protonproton iMQC in water, was considered impossible for many years.
Semiconductor double quantum dot micromaser.
Liu, Y-Y; Stehlik, J; Eichler, C; Gullans, M J; Taylor, J M; Petta, J R
2015-01-16
The coherent generation of light, from masers to lasers, relies upon the specific structure of the individual emitters that lead to gain. Devices operating as lasers in the few-emitter limit provide opportunities for understanding quantum coherent phenomena, from terahertz sources to quantum communication. Here we demonstrate a maser that is driven by single-electron tunneling events. Semiconductor double quantum dots (DQDs) serve as a gain medium and are placed inside a high-quality factor microwave cavity. We verify maser action by comparing the statistics of the emitted microwave field above and below the maser threshold. Copyright © 2015, American Association for the Advancement of Science.
Walborn, S P; Pádua, S; Monken, C H
2002-01-01
We report a quantum eraser experiment which actually uses a Young double-slit to create interference. The experiment can be considered an optical analogy of an experiment proposed by Scully, Englert and Walther. One photon of an entangled pair is incident on a Young double-slit of appropriate dimensions to create an interference pattern in a distant detection region. Quarter-wave plates, oriented so that their fast axes are orthogonal, are placed in front of each slit to serve as which-path markers. The quarter-wave plates mark the polarization of the interfering photon and thus destroy the interference pattern. To recover interference, we measure the polarization of the other entangled photon. In addition, we perform the experiment under delayed erasure circumstances.
A general intermolecular force field based on tight-binding quantum chemical calculations
Grimme, Stefan; Bannwarth, Christoph; Caldeweyher, Eike; Pisarek, Jana; Hansen, Andreas
2017-10-01
A black-box type procedure is presented for the generation of a molecule-specific, intermolecular potential energy function. The method uses quantum chemical (QC) information from our recently published extended tight-binding semi-empirical scheme (GFN-xTB) and can treat non-covalently bound complexes and aggregates with almost arbitrary chemical structure. The necessary QC information consists of the equilibrium structure, Mulliken atomic charges, charge centers of localized molecular orbitals, and also of frontier orbitals and orbital energies. The molecular pair potential includes model density dependent Pauli repulsion, penetration, as well as point charge electrostatics, the newly developed D4 dispersion energy model, Drude oscillators for polarization, and a charge-transfer term. Only one element-specific and about 20 global empirical parameters are needed to cover systems with nuclear charges up to radon (Z = 86). The method is tested for standard small molecule interaction energy benchmark sets where it provides accurate intermolecular energies and equilibrium distances. Examples for structures with a few hundred atoms including charged systems demonstrate the versatility of the approach. The method is implemented in a stand-alone computer code which enables rigid-body, global minimum energy searches for molecular aggregation or alignment.
Institute of Scientific and Technical Information of China (English)
ZHENG SHAO-KUAN; CHEN ZHONG; CHEN ZHI-WEI; ZHONG JIAN-HUI
2001-01-01
A one-dimensional NMR method is presented for measuring the transverse relaxation time, T2,n, of intermolecular multiple quantum coherences (IMQCs) of coherence order n in highly polarized spin systems. The pulse sequence proposed in this paper effectively suppresses the effects of radiation damping, molecular diffusion, inhomogeneity of magnetic field, and variations of dipolar correlation distance, all of which may affect quantitation of T2,n. This pulse sequence can be used to measure not only IMQC transverse relaxation time T2,n(n ＞ 1) quickly and directly, but also the conventional transverse relaxation time. Experimental results demonstrate that the quantitative relationship between T2,n(n≥1) and T2 is T2,n≈T2/n. These results will be helpful for understanding the fundamental properties and mechanisms of IMQCs.
Lin, Meijin; Chen, Xi; Cai, Shuhui; Chen, Zhong
2010-06-21
Intermolecular zero-quantum coherences (iZQCs) have been utilized to achieve high-resolution nuclear magnetic resonance (NMR) proton spectra under inhomogeneous and/or unstable fields. In this paper, we demonstrated that despite the insensitivity of iZQCs to B(0) variations, the influence of unstable fields on the observable single-quantum coherence signals causes strong t(1) noises in the high-resolution iZQC spectra. Short-time acquisition (STA) and phase spectrum schemes were proposed for noise suppression in in vivo iZQC magnetic resonance spectroscopy (MRS) under temporal B(0) variations. The feasibility of these schemes were verified by localized spectroscopic studies under B(0) variations generated by the Z0 coil current oscillations and by voxel position variations in the presence of field gradients, which simulate the field conditions of MRS in the presence of physiological motions. The phase scheme not only improves the signal-to-noise ratio but also further reduces the linewidth by half.
Double-partition Quantum Cluster Algebras
DEFF Research Database (Denmark)
Jakobsen, Hans Plesner; Zhang, Hechun
2012-01-01
A family of quantum cluster algebras is introduced and studied. In general, these algebras are new, but sub-classes have been studied previously by other authors. The algebras are indexed by double parti- tions or double flag varieties. Equivalently, they are indexed by broken lines L. By grouping...... together neighboring mutations into quantum line mutations we can mutate from the cluster algebra of one broken line to another. Compatible pairs can be written down. The algebras are equal to their upper cluster algebras. The variables of the quantum seeds are given by elements of the dual canonical basis....
No fermion doubling in quantum geometry
Energy Technology Data Exchange (ETDEWEB)
Gambini, Rodolfo [Instituto de Física, Facultad de Ciencias, Iguá 4225, esq. Mataojo, 11400 Montevideo (Uruguay); Pullin, Jorge, E-mail: pullin@lsu.edu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)
2015-10-07
In loop quantum gravity the discrete nature of quantum geometry acts as a natural regulator for matter theories. Studies of quantum field theory in quantum space–times in spherical symmetry in the canonical approach have shown that the main effect of the quantum geometry is to discretize the equations of matter fields. This raises the possibility that in the case of fermion fields one could confront the usual fermion doubling problem that arises in lattice gauge theories. We suggest, again based on recent results on spherical symmetry, that since the background space–times will generically involve superpositions of states associated with different discretizations the phenomenon may not arise. This opens a possibility of incorporating chiral fermions in the framework of loop quantum gravity.
Institute of Scientific and Technical Information of China (English)
FENG Hai; ZHANG Sheng-Chun; CAI Shu-Hui; CHEN Zhong; FENG Ji
2007-01-01
The solvent peak in the intermolecular multiple-quantum coherence spectra can be suppressed by either applying pulse field gradients or spinning sample along the magic angle direction((δ)=54.7).However,these two methods also suppress the signals of the solute.We design two pulse sequences with only z-axis gradients to suppress the solvent peak without reducing the intensity of solute signals.Compared to the former pulse sequence,the latter pulse sequence is insensitive to the imperfection of pulse flip angles.When the flip angles of the second pulse sequence are purposely deviated 1/10 from the optimal values,the solvent peak is still weak.Theoretical expressions,experimental observations and computer simulations demonstrate that the two methods can be used to effectively suppress solvent peak in intermolecular multiple-quantum coherence spectra.
Anisotropy mapping in rat brains using Intermolecular Multiple Quantum Coherence Effects
Han, Yi
2014-01-01
This document reports an unconventional and rapidly developing approach to magnetic resonance imaging (MRI) using intermolecular multiple-quantum coherences (iMQCs). Rat brain images are acquired using iMQCs. We detect iMQCs between spins that are 10 {\\mu}m to 500 {\\mu}m apart. The interaction between spins is dependent on different directions. We can choose the directions on physical Z, Y and X axis by choosing correlation gradients along those directions. As an important application, iMQCs can be used for anisotropy mapping. In the rat brains, we investigate tissue microstructure. We simulated images expected from rat brains without microstructure. We compare those with experimental results to prove that the dipolar field from the overall shape only has small contributions to the experimental iMQC signal. Because of the underlying low signal to noise ratio (SNR) in iMQCs, this anisotropy mapping method still has comparatively large potentials to grow. The ultimate goal of my project is to develop creative a...
In vivo noninvasive detection of Brown Adipose Tissue through intermolecular zero-quantum MRI.
Directory of Open Access Journals (Sweden)
Rosa T Branca
Full Text Available The recent discovery of active Brown Adipose Tissue (BAT in adult humans has opened new avenues for obesity research and treatment, as reduced BAT activity seem to be implicated in human energy imbalance, diabetes, and hypertension. However, clinical applications are currently limited by the lack of non-invasive tools for measuring mass and function of this tissue in humans. Here we present a new magnetic resonance imaging method based on the normally invisible intermolecular multiple-quantum coherence (1H MR signal. This method, which doesn't require special hardware modifications, can be used to overcome partial volume effect, the major limitation of MR-based approaches that are currently being investigated for the detection of BAT in humans. With this method we can exploit the characteristic cellular structure of BAT to selectively image it, even when (as in humans it is intimately mixed with other tissues. We demonstrate and validate this method in mice using PET scans and histology. We compare this methodology with conventional (1H MR fat fraction methods. Finally, we investigate its feasibility for the detection of BAT in humans.
In vivo noninvasive detection of Brown Adipose Tissue through intermolecular zero-quantum MRI.
Branca, Rosa T; Zhang, Le; Warren, Warren S; Auerbach, Edward; Khanna, Arjun; Degan, Simone; Ugurbil, Kamil; Maronpot, Robert
2013-01-01
The recent discovery of active Brown Adipose Tissue (BAT) in adult humans has opened new avenues for obesity research and treatment, as reduced BAT activity seem to be implicated in human energy imbalance, diabetes, and hypertension. However, clinical applications are currently limited by the lack of non-invasive tools for measuring mass and function of this tissue in humans. Here we present a new magnetic resonance imaging method based on the normally invisible intermolecular multiple-quantum coherence (1)H MR signal. This method, which doesn't require special hardware modifications, can be used to overcome partial volume effect, the major limitation of MR-based approaches that are currently being investigated for the detection of BAT in humans. With this method we can exploit the characteristic cellular structure of BAT to selectively image it, even when (as in humans) it is intimately mixed with other tissues. We demonstrate and validate this method in mice using PET scans and histology. We compare this methodology with conventional (1)H MR fat fraction methods. Finally, we investigate its feasibility for the detection of BAT in humans.
Christensen, Anders S.; Kromann, Jimmy C.; Jensen, Jan H.; Cui, Qiang
2017-10-01
To facilitate further development of approximate quantum mechanical methods for condensed phase applications, we present a new benchmark dataset of intermolecular interaction energies in the solution phase for a set of 15 dimers, each containing one charged monomer. The reference interaction energy in solution is computed via a thermodynamic cycle that integrates dimer binding energy in the gas phase at the coupled cluster level and solute-solvent interaction with density functional theory; the estimated uncertainty of such calculated interaction energy is ±1.5 kcal/mol. The dataset is used to benchmark the performance of a set of semi-empirical quantum mechanical (SQM) methods that include DFTB3-D3, DFTB3/CPE-D3, OM2-D3, PM6-D3, PM6-D3H+, and PM7 as well as the HF-3c method. We find that while all tested SQM methods tend to underestimate binding energies in the gas phase with a root-mean-squared error (RMSE) of 2-5 kcal/mol, they overestimate binding energies in the solution phase with an RMSE of 3-4 kcal/mol, with the exception of DFTB3/CPE-D3 and OM2-D3, for which the systematic deviation is less pronounced. In addition, we find that HF-3c systematically overestimates binding energies in both gas and solution phases. As most approximate QM methods are parametrized and evaluated using data measured or calculated in the gas phase, the dataset represents an important first step toward calibrating QM based methods for application in the condensed phase where polarization and exchange repulsion need to be treated in a balanced fashion.
Double Acceptor Interaction in Semimagnetic Quantum Dot
Directory of Open Access Journals (Sweden)
A. Merwyn Jasper D. Reuben
2011-01-01
Full Text Available The effect of geometry of the semimagnetic Quantum Dot on the Interaction energy of a double acceptor is computed in the effective mass approximation using the variational principle. A peak is observed at the lower dot sizes as a magnetic field is increased which is attributed to the reduction in confinement.
Rau, D C; Parsegian, V A
1992-01-01
Rather than acting by modifying van der Waals or electrostatic double layer interactions or by directly bridging neighboring molecules, polyvalent ligands bound to DNA double helices appear to act by reconfiguring the water between macromolecular surfaces to create attractive long range hydration forces. We have reached this conclusion by directly measuring the repulsive forces between parallel B-form DNA double helices pushed together from the separations at which they have self organized into hexagonal arrays of parallel rods. For all of the wide variety of "condensing agents" from divalent Mn to polymeric protamines, the resulting intermolecular force varies exponentially with a decay rate of 1.4-1.5 A, exactly one-half that seen previously for hydration repulsion. Such behavior qualitatively contradicts the predictions of all electrostatic double layer and van der Waals force potentials previously suggested. It fits remarkably well with the idea, developed and tested here, that multivalent counterion adsorption reorganizes the water at discrete sites complementary to unadsorbed sites on the apposing surface. The measured strength and range of these attractive forces together with their apparent specificity suggest the presence of a previously unexpected force in molecular organization.
The small quantum group as a quantum double
Etingof, Pavel; Gelaki, Shlomo
2009-01-01
We prove that the quantum double of the quasi-Hopf algebra A_q(g) of dimension n^{dim g} attached in arXiv:math/0403096 to a simple complex Lie algebra g and a primitive root of unity q of order n^2 is equivalent to Lusztig's small quantum group u_q(g) (under some conditions on n). We also give a conceptual construction of A_q(g) using the notion of de-equivariantization of tensor categories.
Local Gate Control of a Carbon Nanotube Double Quantum Dot
2016-04-04
Nanotube Double Quantum Dot N. Mason,*† M. J. Biercuk,* C. M. Marcus† We have measured carbon nanotube quantum dots with multiple electro- static gates and...used the resulting enhanced control to investigate a nano- tube double quantum dot. Transport measurements reveal honeycomb charge stability diagrams...This ability to control electron interactions in the quantum regime in a molecular conductor is important for applications such as quantum
Doubles of Quasi-Quantum Groups
Hausser, F; Hausser, Frank; Nill, Florian
1999-01-01
Drinfeld showed that any finite dimensional Hopf algebra \\G extends to a quasitriangular Hopf algebra \\D(\\G), the quantum double of \\G. Based on the construction of a so--called diagonal crossed product developed by the authors, we generalize this result to the case of quasi--Hopf algebras \\G. As for ordinary Hopf algebras, as a vector space the ``quasi--quantum double'' \\D(\\G) is isomorphic to the tensor product of \\G and its dual \\dG. We give explicit formulas for the product, the coproduct, the R--matrix and the antipode on quasi--Hopf algebra. In particular \\D(\\G) becomes an associative algebra containing \\G as a quasi--Hopf subalgebra. On the other hand, \\dG øtimes 1 is not a subalgebra of \\D(\\G) unless the coproduct on \\G is strictly coassociative. It is shown that the category of finite dimensional representations of \\D(\\G) coincides with what has been called the double category of \\G--modules by S. Majid [M2]. Thus our construction gives a concrete realization of Majid's abstract definition of quasi-...
Chavda, Bhavin R.; Gandhi, Sahaj A.; Dubey, Rahul P.; Patel, Urmila H.; Barot, Vijay M.
2016-05-01
The novel chalcone derivatives have widespread applications in material science and medicinal industries. The density functional theory (DFT) is used to optimized the molecular structure of the three chalcone derivatives (M-I, II, III). The observed discrepancies between the theoretical and experimental (X-ray data) results attributed to different environments of the molecules, the experimental values are of the molecule in solid state there by subjected to the intermolecular forces, like non-bonded hydrogen bond interactions, where as isolated state in gas phase for theoretical studies. The lattice energy of all the molecules have been calculated using PIXELC module in Coulomb -London -Pauli (CLP) package and is partitioned into corresponding coulombic, polarization, dispersion and repulsion contributions. Lattice energy data confirm and strengthen the finding of the X-ray results that the weak but significant intermolecular interactions like C-H…O, Π- Π and C-H… Π plays an important role in the stabilization of crystal packing.
Terahertz detection using double quantum well devices
Khodier, Majid; Christodoulou, Christos G.; Simmons, Jerry A.
2001-12-01
This paper discusses the principle of operation of an electrically tunable THz detector, working around 2.54 THz, integrated with a bowtie antenna. The detection is based on the idea of photon-assisted tunneling (PAT) in a double quantum well (DQW) device. The bowtie antenna is used to collect the THz radiation and feed it to the detector for processing. The Bowtie antenna geometry is integrated with the DQW device to achieve broadband characteristic, easy design, and compatibility with the detector fabrication process. The principle of operation of the detector is introduced first. Then, results of different bowtie antenna layouts are presented and discussed.
Energy Technology Data Exchange (ETDEWEB)
Chavda, Bhavin R., E-mail: chavdabhavin9@gmail.com; Dubey, Rahul P.; Patel, Urmila H. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388120, Gujarat (India); Gandhi, Sahaj A. [Bhavan’s Shri I.L. Pandya Arts-Science and Smt. J.M. shah Commerce College, Dakar, Anand -388001, Gujarat, Indian (India); Barot, Vijay M. [P. G. Center in Chemistry, Smt. S. M. Panchal Science College, Talod, Gujarat 383 215 (India)
2016-05-06
The novel chalcone derivatives have widespread applications in material science and medicinal industries. The density functional theory (DFT) is used to optimized the molecular structure of the three chalcone derivatives (M-I, II, III). The observed discrepancies between the theoretical and experimental (X-ray data) results attributed to different environments of the molecules, the experimental values are of the molecule in solid state there by subjected to the intermolecular forces, like non-bonded hydrogen bond interactions, where as isolated state in gas phase for theoretical studies. The lattice energy of all the molecules have been calculated using PIXELC module in Coulomb –London –Pauli (CLP) package and is partitioned into corresponding coulombic, polarization, dispersion and repulsion contributions. Lattice energy data confirm and strengthen the finding of the X-ray results that the weak but significant intermolecular interactions like C-H…O, Π- Π and C-H… Π plays an important role in the stabilization of crystal packing.
Theory of intermolecular forces
Margenau, H; Ter Haar, D
1971-01-01
Theory of Intermolecular Forces deals with the exposition of the principles and techniques of the theory of intermolecular forces. The text focuses on the basic theory and surveys other aspects, with particular attention to relevant experiments. The initial chapters introduce the reader to the history of intermolecular forces. Succeeding chapters present topics on short, intermediate, and long range atomic interactions; properties of Coulomb interactions; shape-dependent forces between molecules; and physical adsorption. The book will be of good use to experts and students of quantum mechanics
SU(4) Kondo entanglement in double quantum dot devices
Bonazzola, Rodrigo; Andrade, J. A.; Facio, Jorge I.; García, D. J.; Cornaglia, Pablo S.
2017-08-01
We analyze, from a quantum information theory perspective, the possibility of realizing an SU(4) entangled Kondo regime in semiconductor double quantum dot devices. We focus our analysis on the ground-state properties and consider the general experimental situation where the coupling parameters of the two quantum dots differ. We model each quantum dot with an Anderson-type Hamiltonian including an interdot Coulomb repulsion and tunnel couplings for each quantum dot to independent fermionic baths. We find that the spin and pseudospin entanglements can be made equal, and the SU(4) symmetry recovered, if the gate voltages are chosen in such a way that the average charge occupancies of the two quantum dots are equal, and the double occupancy on the double quantum dot is suppressed. We present density matrix renormalization group numerical results for the spin and pseudospin entanglement entropies, and analytical results for a simplified model that captures the main physics of the problem.
Gates controlled parallel-coupled bilayer graphene double quantum dot
Wang, Lin-Jun; Wei, Da; Cao, Gang; Tu, Tao; Xiao, Ming; Guo, Guang-Can; Chang, A M
2011-01-01
Here we report the fabrication and quantum transport measurements of gates controlled parallel-coupled bilayer graphene double quantum dot. It is shown that the interdot coupling strength of the parallel double dots can be effectively tuned from weak to strong regime by both the in-plane plunger gates and back gate. All the relevant energy scales and parameters of the bilayer graphene parallel-coupled double dot can be extracted from the honeycomb charge stability diagrams revealed through the transport measurements.
Young's Double Slit Experiment in Quantum Field Theory
Kenmoku, Masakatsu
2011-01-01
Young's double slit experiment is formulated in the framework of canonical quantum field theory in view of the modern quantum optics. We adopt quantum scalar fields instead of quantum electromagnetic fields ignoring the vector freedom in gauge theory. The double slit state is introduced in Fock space corresponding to experimental setup. As observables, expectation values of energy density and positive frequency part of current with respect to the double slit state are calculated which give the interference term. Classical wave states are realized by coherent double slit states in Fock space which connect quantum particle states with classical wave states systematically. In case of incoherent sources, the interference term vanishes by averaging random phase angles as expected.
Deformed quantum double realization of the toric code and beyond
Padmanabhan, Pramod; Ibieta-Jimenez, Juan Pablo; Bernabe Ferreira, Miguel Jorge; Teotonio-Sobrinho, Paulo
2016-09-01
Quantum double models, such as the toric code, can be constructed from transfer matrices of lattice gauge theories with discrete gauge groups and parametrized by the center of the gauge group algebra and its dual. For general choices of these parameters the transfer matrix contains operators acting on links which can also be thought of as perturbations to the quantum double model driving it out of its topological phase and destroying the exact solvability of the quantum double model. We modify these transfer matrices with perturbations and extract exactly solvable models which remain in a quantum phase, thus nullifying the effect of the perturbation. The algebra of the modified vertex and plaquette operators now obey a deformed version of the quantum double algebra. The Abelian cases are shown to be in the quantum double phase whereas the non-Abelian phases are shown to be in a modified phase of the corresponding quantum double phase. These are illustrated with the groups Zn and S3. The quantum phases are determined by studying the excitations of these systems namely their fusion rules and the statistics. We then go further to construct a transfer matrix which contains the other Z2 phase namely the double semion phase. More generally for other discrete groups these transfer matrices contain the twisted quantum double models. These transfer matrices can be thought of as being obtained by introducing extra parameters into the transfer matrix of lattice gauge theories. These parameters are central elements belonging to the tensor products of the algebra and its dual and are associated to vertices and volumes of the three dimensional lattice. As in the case of the lattice gauge theories we construct the operators creating the excitations in this case and study their braiding and fusion properties.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Strong and extremely homogeneous static magnetic field is usually required for high-resolution nu-clear magnetic resonance (NMR). However, in the cases of in vivo and so on, the magnetic field inho-mogeneity owing to magnetic susceptibility variation in samples is unavoidable and hard to eliminate by conventional methods such as shimming. Recently, intermolecular multiple quantum coherences (iMQCs) have been employed to eliminate inhomogeneous broadening and obtain high-resolution NMR spectra, especially for in vivo samples. Compared to other high-resolution NMR methods, iMQC method exhibits its unique feature and advantage. It simultaneously holds information of chemical shifts, multiplet structures, coupling constants, and relative peak areas. All the information is often used to analyze and characterize molecular structures in conventional one-dimensional NMR spec-troscopy. In this work, recent technical developments including our results in this field are summarized; the high-resolution mechanism is analyzed and comparison with other methods based on interactions between spins is made; comments on the current situation and outlook on the research directions are also made.
A Portable Double-Slit Quantum Eraser with Individual Photons
Dimitrova, T. L.; Weis, A.
2011-01-01
The double-slit experiment has played an important role in physics, from supporting the wave theory of light, via the discussions of the wave-particle duality of light (and matter) to the foundations of modern quantum optics. Today it keeps playing an active role in the context of quantum optics experiments involving single photons. In this paper,…
Vertically coupled double quantum rings at zero magnetic field
Malet i Giralt, Francesc; Barranco Gómez, Manuel; Lipparini, Enrico; Mayol Sánchez, Ricardo; Pi Pericay, Martí; Climente, J. I.; Planelles, Josep
2006-01-01
Within local-spin-density functional theory, we have investigated the `dissociation' of few-electron circular vertical semiconductor double quantum ring artificial molecules at zero magnetic field as a function of inter-ring distance. In a first step, the molecules are constituted by two identical quantum rings. When the rings are quantum mechanically strongly coupled, the electronic states are substantially delocalized, and the addition energy spectra of the artificial molecule resemble thos...
Spins of Andreev states in double quantum dots
Su, Zhaoen; Chen, Jun; Yu, Peng; Hocervar, Moira; Plissard, Sebastien; Car, Diana; Tacla, Alexandre; Daley, Andrew; Pekker, David; Bakkers, Erik; Frolov, Sergey
Andreev (or Shiba) states in coupled double quantum dots is an open field. Here we demonstrate the realization of Andreev states in double quantum dots in an InSb nanowire coupled to two NbTiN superconductors. The magnetic field dependence of the Andreev states has been explored to resolve the spins in different double dot configurations. The experiment helps to understand the interplay between pair correlation, exchange energy and charging energy with a well-controlled system. It also opens the possibility to implement Majorana modes in Kitaev chains made of such dots.
A portable double-slit quantum eraser with individual photons
Energy Technology Data Exchange (ETDEWEB)
Dimitrova, T L [Physics Faculty, University of Plovdiv ' Paissi Hilendarski' , Tzar Assen Str. 24, BG-4000 Plovdiv (Bulgaria); Weis, A, E-mail: doradimitrova@uni-plovdiv.bg [Physics Department, University of Fribourg, Chemin du Musee 3, CH-1700 Fribourg (Switzerland)
2011-11-15
The double-slit experiment has played an important role in physics, from supporting the wave theory of light, via the discussions of the wave-particle duality of light (and matter) to the foundations of modern quantum optics. Today it keeps playing an active role in the context of quantum optics experiments involving single photons. In this paper, we present a truly portable double-slit apparatus which demonstrates both the wave-particle duality of light and the phenomenon of quantum erasing. The device can be operated either with strong laser light and screen projection, or with individual photons, in which case quantum interference and quantum erasing are detected by a photomultiplier whose pulses are rendered acoustically by means of a loudspeaker. Alternatively, the phenomena can be displayed using multimedia projection of oscilloscope traces.
Krovi, Hari; Russell, Alexander
2012-01-01
Knot and link invariants naturally arise from any braided Hopf algebra. We consider the computational complexity of the invariants arising from an elementary family of finite-dimensional Hopf algebras: quantum doubles of finite groups (denoted D(G), for a group G). Regarding algorithms for these invariants, we develop quantum circuits for the quantum Fourier transform over D(G); in general, we show that when one can uniformly and efficiently carry out the quantum Fourier transform over the ce...
Andreev molecules in semiconductor nanowire double quantum dots.
Su, Zhaoen; Tacla, Alexandre B; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Daley, Andrew J; Pekker, David; Frolov, Sergey M
2017-09-19
Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum dots are defined by gate voltages in indium antimonide nanowires. High transparency superconducting niobium titanium nitride contacts are made to each of the dots in order to induce superconductivity, as well as probe electron transport. Andreev bound states induced on each of dots hybridize to define Andreev molecular states. The evolution of these states is studied as a function of charge parity on the dots, and in magnetic field. The experiments are found in agreement with a numerical model.Quantum dots in a nanowire are one possible approach to creating a solid-state quantum simulator. Here, the authors demonstrate the coupling of electronic states in a double quantum dot to form Andreev molecule states; a potential building block for longer chains suitable for quantum simulation.
Multiple Nuclear Polarization States in a Double Quantum Dot
Danon, J.; Vink, I.T.; Koppens, F.H.L.; Nowack, K.C.; Vandersypen, L.M.K.; Nazarov, Y.V.
2009-01-01
We observe multiple stable states of nuclear polarization and nuclear self-tuning over a large range of fields in a double quantum dot under conditions of electron spin resonance. The observations can be understood within an elaborated theoretical rate equation model for the polarization in each of
High sensitivity double relaxation oscillation superconducting quantum interference devices
Adelerhof, Derk Jan; Adelerhof, Derk Jan; Kawai, Jun; Uehara, Gen; Kado, Hisashi
1994-01-01
Double relaxation oscillationsuperconducting quantum interference devices(SQUIDs) (DROSs) have been fabricated with estimated relaxation frequencies up to 14 GHz. Both the intrinsic flux noise and the performance in a flux locked loop with direct voltage readout have been studied. In flux locked
Bose Condensation of Interwell Excitons in Double Quantum Wells
DEFF Research Database (Denmark)
Larionov, A. V.; Timofeev, V. B.; Ni, P. A.
2002-01-01
The luminescence of interwell excitons in double quantum wells GaAs/AlGaAs (n–i–n heterostructures) with large-scale fluctuations of random potential in the heteroboundary planes was studied. The properties of excitons whose photoexcited electron and hole are spatially separated in the neighboring...
Perturbative quantum gravity in double field theory
Boels, Rutger H.; Horst, Christoph
2016-04-01
We study perturbative general relativity with a two-form and a dilaton using the double field theory formulation which features explicit index factorisation at the Lagrangian level. Explicit checks to known tree level results are performed. In a natural covariant gauge a ghost-like scalar which contributes even at tree level is shown to decouple consistently as required by perturbative unitarity. In addition, a lightcone gauge is explored which bypasses the problem altogether. Using this gauge to study BCFW on-shell recursion, we can show that most of the D-dimensional tree level S-matrix of the theory, including all pure graviton scattering amplitudes, is reproduced by the double field theory. More generally, we argue that the integrand may be reconstructed from its single cuts and provide limited evidence for off-shell cancellations in the Feynman graphs. As a straightforward application of the developed technology double field theory-like expressions for four field string corrections are derived.
Perturbative quantum gravity in double field theory
Boels, Rutger H
2015-01-01
We study perturbative general relativity with a two-form and a dilaton using the double field theory formulation which features explicit index factorisation at the Lagrangian level. Explicit checks to known tree level results are performed. In a natural covariant gauge a ghost-like scalar which contributes even at tree level is shown to decouple consistently as required by perturbative unitarity. In addition, a lightcone gauge is explored which bypasses the problem altogether. Using this gauge to study BCFW on-shell recursion, we can show that most of the D-dimensional tree level S-matrix of the theory, including all pure graviton scattering amplitudes, is reproduced by the double field theory. More generally, we argue that the integrand may be reconstructed from its single cuts and provide limited evidence for off-shell cancellations in the Feynman graphs. As a straightforward application of the developed technology double field theory-like expressions for four field string corrections are derived.
Simulating electron spin entanglement in a double quantum dot
Rodriguez-Moreno, M. A.; Hernandez de La Luz, A. D.; Meza-Montes, Lilia
2011-03-01
One of the biggest advantages of having a working quantum-computing device when compared with a classical one, is the exponential speedup of calculations. This exponential increase is based on the ability of a quantum system to create and operate on entangled states. In order to study theoretically the entanglement between two electron spins, we simulate the dynamics of two electron spins in an electrostatically-defined double quantum dot with a finite barrier height between the dots. Electrons are initially confined to separated quantum dots. Barrier height is varied and the spin entanglement as a function of this variation is investigated. The evolution of the system is simulated by using a numerical approach for solving the time-dependent Schrödinger equation for two particles. Partially supported by VIEP-BUAP.
A fast "hybrid" silicon double quantum dot qubit
Shi, Zhan; Prance, J R; Gamble, John King; Koh, Teck Seng; Shim, Yun-Pil; Hu, Xuedong; Savage, D E; Lagally, M G; Eriksson, M A; Friesen, Mark; Coppersmith, S N
2011-01-01
We propose a quantum dot qubit architecture that has an attractive combination of speed and fabrication simplicity. It consists of a double quantum dot with one electron in one dot and two electrons in the other. The qubit itself is a set of two states with total spin quantum numbers $S^2=3/4$ ($S=\\half$) and $S_z = -\\half$, with the two different states being singlet and triplet in the doubly occupied dot. The architecture is relatively simple to fabricate, a universal set of fast operations can be implemented electrically, and the system has potentially long decoherence times. These are all extremely attractive properties for use in quantum information processing devices.
RKKY interaction in a chirally coupled double quantum dot system
Energy Technology Data Exchange (ETDEWEB)
Heine, A. W.; Tutuc, D.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany); Zwicknagl, G. [Institut für Mathematische Physik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig (Germany); Schuh, D. [Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätstr. 31, 93053 Regensburg (Germany); Wegscheider, W. [Laboratorium für Festkörperphysik, ETH Zürich, Schafmattstr. 16, 8093 Zürich, Switzerland and Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätstr. 31, 93053 Regens (Germany)
2013-12-04
The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the so-called Kondo chessboard pattern in the transport through the quantum dots. The two quantum dots become therefore chirally coupled via the edge channels formed in the open conducting area. In regions where both quantum dots exhibit Kondo transport the presence of the RKKY exchange interaction is probed by an analysis of the temperature dependence. The thus obtained Kondo temperature of one dot shows an abrupt increase at the onset of Kondo transport in the other, independent of the magnetic field polarity, i.e. edge state chirality in the central region.
QCAD simulation and optimization of semiconductor double quantum dots
Energy Technology Data Exchange (ETDEWEB)
Nielsen, Erik; Gao, Xujiao; Kalashnikova, Irina; Muller, Richard Partain; Salinger, Andrew Gerhard; Young, Ralph Watson
2013-12-01
We present the Quantum Computer Aided Design (QCAD) simulator that targets modeling quantum devices, particularly silicon double quantum dots (DQDs) developed for quantum qubits. The simulator has three di erentiating features: (i) its core contains nonlinear Poisson, e ective mass Schrodinger, and Con guration Interaction solvers that have massively parallel capability for high simulation throughput, and can be run individually or combined self-consistently for 1D/2D/3D quantum devices; (ii) the core solvers show superior convergence even at near-zero-Kelvin temperatures, which is critical for modeling quantum computing devices; (iii) it couples with an optimization engine Dakota that enables optimization of gate voltages in DQDs for multiple desired targets. The Poisson solver includes Maxwell- Boltzmann and Fermi-Dirac statistics, supports Dirichlet, Neumann, interface charge, and Robin boundary conditions, and includes the e ect of dopant incomplete ionization. The solver has shown robust nonlinear convergence even in the milli-Kelvin temperature range, and has been extensively used to quickly obtain the semiclassical electrostatic potential in DQD devices. The self-consistent Schrodinger-Poisson solver has achieved robust and monotonic convergence behavior for 1D/2D/3D quantum devices at very low temperatures by using a predictor-correct iteration scheme. The QCAD simulator enables the calculation of dot-to-gate capacitances, and comparison with experiment and between solvers. It is observed that computed capacitances are in the right ballpark when compared to experiment, and quantum con nement increases capacitance when the number of electrons is xed in a quantum dot. In addition, the coupling of QCAD with Dakota allows to rapidly identify which device layouts are more likely leading to few-electron quantum dots. Very efficient QCAD simulations on a large number of fabricated and proposed Si DQDs have made it possible to provide fast feedback for design
Buckingham, A D
1975-11-06
The nature of molecular interactions is examined. Intermolecular forces are divided into long-range and short-range components; the former operate at distances where the effects of electron exchange are negligible and decrease as an inverse power of the separation. The long-range interactions may be subdividied into electrostatic, induction and dispersion contributions, where the electrostatic component is the interaction of the permanent charge distributions and the others originate in the fluctuations in the distributions. Typical magnitudes of the various contributions are given. The forces between macroscopic bodies are briefly considered, as are the effects of a medium. Some of the manifestations of molecular interactions are discussed.
The breaking of quantum double symmetries by defect condensation
Bais, F. A.; Mathy, C. J. M.
2007-03-01
In this paper, we study the phenomenon of Hopf or more specifically quantum double symmetry breaking. We devise a criterion for this type of symmetry breaking which is more general than the one originally proposed in F.A. Bais, B.J. Schroers, J.K. Slingerland [Broken quantum symmetry and confinement phases in planar physics, Phys. Rev. Lett. 89 (2002) 181601]; Hopf symmetry breaking and confinement in (2+1)-dimensional gauge theory, JHEP 05 (2003) 068], and therefore extends the number of possible breaking patterns that can be described consistently. We start by recalling why the extended symmetry notion of quantum double algebras is an optimal tool when analyzing a wide variety of two-dimensional physical systems including quantum fluids, crystals and liquid crystals. The power of this approach stems from the fact that one may characterize both ordinary and topological modes as representations of a single (generally nonabelian) Hopf symmetry. In principle a full classification of defect mediated as well as ordinary symmetry breaking patterns and subsequent confinement phenomena can be given. The formalism applies equally well to systems exhibiting global, local, internal and/or external (i.e. spatial) symmetries. The subtle differences in interpretation for the various situations are pointed out. We show that the Hopf symmetry breaking formalism reproduces the known results for ordinary (electric) condensates, and we derive formulae for defect (magnetic) condensates which also involve the phenomenon of symmetry restoration. These results are applied in two papers which will be published in parallel [C.J.M. Mathy, F.A. Bais, Nematic phases and the breaking of double symmetries, arXiv:cond-mat/0602109, 2006; F.A. Bais, C.J.M. Mathy, Defect mediated melting and the breaking of quantum double symmetries, arXiv:cond-mat/0602101, 2006].
Heisenberg double of supersymmetric algebras for noncommutative quantum field theory
Kirchanov, V. S.
2013-09-01
The ground work is laid for the construction of a Heisenberg superdouble in the form of a smash product of a standard Poincaré-Lie quantum-operator superalgebra with coalgebra and its double Lie spatial superalgebra with coalgebra, which are Hopf algebras and a Hopf modular algebra, respectively. Deformation of the superalgebras is realized by Drinfeld twists for the shift and supershift operators. As a result, an extended algebra is obtained, containing a non(anti)commutative superspace and quantum-group generators.
Quantum Theory of Electronic Double-Slit Diffraction
Institute of Scientific and Technical Information of China (English)
WU Xiang-Yao; GUO Yi-Qing; ZHANG Bai-Jun; LI Hai-Bo; LU Jing-Bin; LIU Xiao-Jing; WANG Li; ZHANG Chun-Li; LIU Bing; FAN Xi-Hui
2007-01-01
Phenomena of electron, neutron, atomic and molecular diffraction have been studied in many experiments, and these experiments have been explained by some theoretical works. We study electronic double-slit diffraction with a quantum mechanical approach and obtain the following results: (1) When the ratio of d + a/a = n (n = 1, 2, 3,...),orders n, 2n, 3n,...are missing in diffraction pattern. (2) When the ratio of d+a/a ≠ n (n = 1, 2, 3,...), there is not missing order in diffraction pattern. (3) The slit thickness c has a large affect on the electronic diffraction pattern, which is a new quantum effect. We believe that all the predictions in our work can be tested by the electronic double slit diffraction experiment.
Quantum Computing via Singlet-Triplet Spin Qubits in Nanowire Double Quantum Dots
Institute of Scientific and Technical Information of China (English)
XUE Peng
2011-01-01
We propose a new structure for quantum computing via spin qubits with high fidelity.Each spin qubit corresponds to two electrons in a nanowire double quantum dot,with the singlet and one of the triplets as the logical qubit states.The entangling gate is effected by virtual charge dipole transitions.We include noise to show the feasibility of this scheme under current experimental conditions.
Quantum Size Effects on Two Electrons and Two Holes in Double-Layer Quantum Dots
Institute of Scientific and Technical Information of China (English)
XIE Wen-Fang; ZHU Wu
2002-01-01
We propose a procedure to solve exactly the Schrodinger equation for a system of two electrons and two holes in a double-layer quantum dot by using the method of few-body physics. The features of the low-lying spectra have been deduced based on symmetry. The binding energies of the ground state are obtained as a function of the electron-to-hole mass ratio σ for a few values of the quantum dot size.
Transient Intersubband Optical Absorption in Double Quantum Well Structure
Institute of Scientific and Technical Information of China (English)
WU Bin-He
2005-01-01
The microscopic equations of motion including many-body effects are derived to study the intersubband polarization in the double quantum well structure induced by an ultrafast pumping infrared light. Based on the selfconsistent field theory, the transient probe absorption coefficient is calculated. These calculations are beyond the previous steady-state assumption. Transient probe absorption spectra are calculated under different pumping intensity and various pump probe delay.
Nonlinear double Compton scattering in the full quantum regime
Mackenroth, F
2012-01-01
A detailed analysis of the process of two photon emission by an electron scattered from a high-intensity laser pulse is presented. The calculations are performed in the framework of strong-field QED and include exactly the presence of the laser field, described as a plane wave. We investigate the full quantum regime of interaction, where photon recoil plays an essential role in the emission process, and substantially alters the emitted photon spectra as compared to those in previously-studied regimes. We provide a semiclassical explanation for such differences, based on the possibility of assigning a trajectory to the electron in the laser field before and after each quantum photon emission. Our numerical results indicate the feasibility of investigating experimentally the full quantum regime of nonlinear double Compton scattering with already available plasma-based electron accelerator and laser technology.
Connection between noise and quantum correlations in a double quantum dot
Bodoky, F.; Belzig, W.; Bruder, C.
We investigate the current and noise characteristics of a double quantum dot system. The strong correlations induced by the Coulomb interaction and the Pauli principle create entangled two-electron states and lead to signatures in the transport properties. We show that the interaction parameter Ø,
Computer-automated tuning of semiconductor double quantum dots into the single-electron regime
Baart, T. A.; Eendebak, P. T.; Reichl, C.; Wegscheider, W.; Vandersypen, L. M. K.
2016-05-01
We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.
Computer-automated tuning of semiconductor double quantum dots into the single-electron regime
Baart, T.A.; Eendebak, P.T.; Reichl, C.; Wegscheider, W.; Vandersypen, L.M.K.
2016-01-01
We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the
Some double resonance and multiple quantum NMR studies in solids
Energy Technology Data Exchange (ETDEWEB)
Wemmer, D.E.
1978-08-01
The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of /sup 13/C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D/sub 2/O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, ..delta..sigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO/sub 3/.D/sub 2/O, ..cap alpha..,..beta.. d-2 HMB and ..cap alpha..,..beta..,..gamma.. d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules ..delta..m = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made.
Wei, Hai-Rui; Deng, Fu-Guo
2013-07-29
We investigate the possibility of achieving scalable photonic quantum computing by the giant optical circular birefringence induced by a quantum-dot spin in a double-sided optical microcavity as a result of cavity quantum electrodynamics. We construct a deterministic controlled-not gate on two photonic qubits by two single-photon input-output processes and the readout on an electron-medium spin confined in an optical resonant microcavity. This idea could be applied to multi-qubit gates on photonic qubits and we give the quantum circuit for a three-photon Toffoli gate. High fidelities and high efficiencies could be achieved when the side leakage to the cavity loss rate is low. It is worth pointing out that our devices work in both the strong and the weak coupling regimes.
Electron transport in coupled double quantum wells and wires
Energy Technology Data Exchange (ETDEWEB)
Harff, N.E.; Simmons, J.A.; Lyo, S.K. [and others
1997-04-01
Due to inter-quantum well tunneling, coupled double quantum wells (DQWs) contain an extra degree of electronic freedom in the growth direction, giving rise to new transport phenomena not found in single electron layers. This report describes work done on coupled DQWs subject to inplane magnetic fields B{sub {parallel}}, and is based on the lead author`s doctoral thesis, successfully defended at Oregon State University on March 4, 1997. First, the conductance of closely coupled DQWs in B{sub {parallel}} is studied. B{sub {parallel}}-induced distortions in the dispersion, the density of states, and the Fermi surface are described both theoretically and experimentally, with particular attention paid to the dispersion anticrossing and resulting partial energy gap. Measurements of giant distortions in the effective mass are found to agree with theoretical calculations. Second, the Landau level spectra of coupled DQWs in tilted magnetic fields is studied. The magnetoresistance oscillations show complex beating as Landau levels from the two Fermi surface components cross the Fermi level. A third set of oscillations resulting from magnetic breakdown is observed. A semiclassical calculation of the Landau level spectra is then performed, and shown to agree exceptionally well with the data. Finally, quantum wires and quantum point contacts formed in DQW structures are investigated. Anticrossings of the one-dimensional DQW dispersion curves are predicted to have interesting transport effects in these devices. Difficulties in sample fabrication have to date prevented experimental verification. However, recently developed techniques to overcome these difficulties are described.
Dephasing and hyperfine interaction in carbon nanotubes double quantum dots
DEFF Research Database (Denmark)
Reynoso, Andres Alejandro; Flensberg, Karsten
2012-01-01
We study theoretically the return probability experiment, which is used to measure the dephasing time T-2*, in a double quantum dot (DQD) in semiconducting carbon nanotubes with spin-orbit coupling and disorder-induced valley mixing. Dephasing is due to hyperfine interaction with the spins of the C......-13 nuclei. Due to the valley and spin degrees of freedom, four bounded states exist for any given longitudinal mode in the quantum dot. At zero magnetic field, the spin-orbit coupling and the valley mixing split those four states into two Kramers doublets. The valley-mixing term for a given dot...... is determined by the intradot disorder; this leads to (i) states in the Kramers doublets belonging to different dots being different, and (ii) nonzero interdot tunneling amplitudes between states belonging to different doublets. We show that these amplitudes give rise to new avoided crossings, as a function...
Spin-dependent thermoelectric transport through double quantum dots
Institute of Scientific and Technical Information of China (English)
Wang Qiang; Xie Hai-Qing; Jiao Hu-Jun; Li Zhi-Jian; Nie Yi-Hang
2012-01-01
We study the thermoelectric transport through a double-quantum-dot system with spin-dependent interdot coupling and ferromagnetic electrodes by means of the non-equilibrium Green's function in the linear response regime.It is found that the thermoelectric coefficients are strongly dependent on the splitting of the interdot coupling,the relative magnetic configurations,and the spin polarization of leads.In particular,the thermoelectric efficiency can reach a considerable value in the parallel configuration when the effective interdot coupling and the tunnel coupling between the quantum dots and the leads for the spin-down electrons are small.Moreover,the thermoelectric efficiency increases with the intradot Coulomb interaction increasing and can reach very high values at appropriate temperatures.In the presence of the magnetic field,the spin accumulation in the leads strongly suppresses the thermoelectric efficiency,and a pure spin thermopower can be obtained.
Non-equilibrium Kondo effect in double quantum dot
Energy Technology Data Exchange (ETDEWEB)
Kiselev, M.N. E-mail: kiselev@physik.uni-wuerzburg.de; Kikoin, K.A.; Molenkamp, L.W
2004-05-01
We investigate theoretically a non-equilibrium transport through a double quantum dot (DQD) in a parallel geometry. It is shown that the resonance Kondo tunneling through a parallel DQD with even occupation and singlet ground state may arise at a strong bias, which compensates the energy of singlet/triplet excitation. Using the renormalization group technique we derive scaling equations and calculate the differential conductance as a function of an auxiliary DC-bias for parallel DQD being in a regime described by SO(4) symmetry.
The Representations of Quantum Double of Dihedral Groups
Dong, Jingcheng
2011-01-01
Let $k$ be an algebraically closed field of odd characteristic $p$, and let $D_n$ be the dihedral group of order $2n$ such that $p\\mid 2n$. Let $D(kD_n)$ denote the quantum double of the group algebra $kD_n$. In this paper, we describe the structures of all finite dimensional indecomposable left $D(kD_n)$-modules, equivalently, of all finite dimensional indecomposable Yetter-Drinfeld $kD_n$-modules, and classify them.
Double-layer-gate architecture for few-hole GaAs quantum dots
Wang, D. Q.; Hamilton, A. R.; Farrer, I.; Ritchie, D. A.; Klochan, O.
2016-08-01
We report the fabrication of single and double hole quantum dots using a double-layer-gate design on an undoped accumulation mode {{Al}}x{{Ga}}1-x{As}/GaAs heterostructure. Electrical transport measurements of a single quantum dot show varying addition energies and clear excited states. In addition, the two-level-gate architecture can also be configured into a double quantum dot with tunable inter-dot coupling.
Ac response of a coupled double quantum dot
Institute of Scientific and Technical Information of China (English)
Xu Jie; W.Z. Shangguan; Zhan Shi-Chang
2005-01-01
The effect of phase-breaking process on the ac response of a coupled double quantum dot is studied in this paper based on the nonequilibrium Green function formalism. A general expression is derived for the ac current in the presence of electron-phonon interaction. The ac conductance is numerically computed and the results are compared with those in [Anatram M P and Datts S 1995 Phys. Rev. B 51 7632]. Our results reveal that the inter-dot electron tunnelling interplays with that between dots and electron reservoirs, and contributes prominently to the ac current when inter-dot tunnelling coupling is much larger than the tunnelling coupling between dots and electron reservoirs. In addition, the phase-breaking process is found to have a significant effect on the ac transport through the coupled double dot.
Polarization converters on double hetero structures containing strained quantum wells
Khalique, U.; van der Tol, J. J. G. M.; Nötzel, R.; Smit, M. K.
2009-02-01
The importance of polarization manipulation is increased as optical fiber systems evolve to higher data rates. Photonic integrated circuits should be insensitive to the state of polarization of the light emanating from fibers if they are to be used as detectors, add-drop mutiplexers or cross connects. Either all the integrated components have to be polarization independent or only one polarization direction should be used. For either method, a compact polarization converter is useful. A model is developed for the mode propagation in the waveguide of the slanted side polarization converter based on double hetero structures. The model is extended to include polarization dependent absorption and mismatch. Polarization converters on different double heterostructures (with and without quantum wells) have been designed and are realized by contact optical lithography. The performance of the realized converters is well described with the model.
Energy Technology Data Exchange (ETDEWEB)
Dittmer, Jens [Institut de Chimie Moleculaire et Biologique, Ecole Polytechnique Federale de Lausanne, BCH (Switzerland); Kim, Chul-Hyun [University of California, Department of Chemistry (United States); Bodenhausen, Geoffrey [Institut de Chimie Moleculaire et Biologique, Ecole Polytechnique Federale de Lausanne, BCH (Switzerland)], E-mail: Geoffrey.Bodenhausen@ens.fr
2003-07-15
The bond lengths and dynamics of intra- and intermolecular hydrogen bonds in an RNA kissing complex have been characterized by determining the NMR relaxation rates of various double- and triple-quantum coherences that involve an imino proton and two neighboring nitrogen-15 nuclei belonging to opposite bases. New experiments allow one to determine the chemical shift anisotropy of the imino protons. The bond lengths derived from dipolar relaxation and the lack of modulations of the nitrogen chemical shifts indicate that the intermolecular hydrogen bonds which hold the kissing complex together are very similar to the intramolecular hydrogen bonds in the double-stranded stem of the RNA.
Tollerud, Jonathan O
2016-01-01
We identify carrier scattering at densities below which it has previously been observed in semiconductor quantum wells. These effects are evident in the peakshapes of 2D double-quantum spectra, which change as a function of excitation density. At high excitation densities ($\\geq 10^{9}$ carriers/,cm$^{-2}$) we observe untilted peaks similar to those reported in previous experiments. At low excitation densities (<$10^{8}$ carriers cm$^{-2}$) we observe narrower, tilted peaks. Using a simple simulation, we show that tilted peak-shapes are expected in double-quantum spectra when inhomogeneous broadening is much larger than homogeneous broadening, and that fast pure-decoherence of the double-quantum coherence can obscure this peak tilt. These results show that carrier interactions are important at lower densities than previously expected, and that the `natural' double-quantum peakshapes are hidden by carrier interactions at the excitation densities typically used. Furthermore, these results demonstrate that an...
Quantum efficiency of a single microwave photon detector based on a semiconductor double quantum dot
Wong, Clement H.; Vavilov, Maxim G.
2017-01-01
Motivated by recent interest in implementing circuit quantum electrodynamics with semiconducting quantum dots, we consider a double quantum dot (DQD) capacitively coupled to a superconducting resonator that is driven by the microwave field of a superconducting transmission line. We analyze the DQD current response using input-output theory and show that the resonator-coupled DQD is a sensitive microwave single photon detector. Using currently available experimental parameters of DQD-resonator coupling and dissipation, including the effects of 1 /f charge noise and phonon noise, we determine the parameter regime for which incident photons are completely absorbed and near-unit ≳98 % efficiency can be achieved. We show that this regime can be reached by using very high quality resonators with quality factor Q ≃105 .
Photoelectric Characteristics of Double Barrier Quantum Dots-Quantum Well Photodetector
Directory of Open Access Journals (Sweden)
M. J. Wang
2015-01-01
Full Text Available The photodetector based on double barrier AlAs/GaAs/AlAs heterostructures and a layer self-assembled InAs quantum dots and In0.15Ga0.85As quantum well (QW hybrid structure is demonstrated. The detection sensitivity and detection ability under weak illuminations have been proved. The dark current of the device can remain at 0.1 pA at 100 K, even lower to 3.05×10-15 A, at bias of −1.35 V. Its current responsivity can reach about 6.8×105 A/W when 1 pw 633 nm light power and −4 V bias are added. Meanwhile a peculiar amplitude quantum oscillation characteristic is observed in testing. A simple model is used to qualitatively describe. The results demonstrate that the InAs monolayer can effectively absorb photons and the double barrier hybrid structure with quantum dots in well can be used for low-light-level detection.
Zhang, Rongchun; Duong, Nghia Tuan; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy
2017-06-22
Solid-state (1)H NMR spectroscopy has attracted much attention in the recent years due to the remarkable spectral resolution improvement by ultrafast magic-angle-spinning (MAS) as well as due to the sensitivity enhancement rendered by proton detection. Although these developments have enabled the investigation of a variety of challenging chemical and biological solids, the proton spectral resolution is still poor for many rigid solid systems owing to the presence of conformational heterogeneity and the unsuppressed residual proton-proton dipolar couplings even with the use of the highest currently feasible sample spinning speed of ∼130 kHz. Although a further increase in the spinning speed of the sample could be beneficial to some extent, there is a need for alternate approaches to enhance the spectral resolution. Herein, by fully utilizing the benefits of double-quantum (DQ) coherences, we propose a single radio frequency channel proton-based 3D pulse sequence that correlates double-quantum (DQ), DQ, and single-quantum (SQ) chemical shifts of protons. In addition to the two-spin homonuclear proximity information, the proposed 3D DQ/DQ/SQ experiment also enables the extraction of three-spin and four-spin proximities, which could be beneficial for revealing the dipolar coupled proton network in the solid state. Besides, the 2D DQ/DQ spectrum sliced at different isotropic SQ chemical shift values of the 3D DQ/DQ/SQ spectrum will also facilitate the identification of DQ correlation peaks and improve the spectral resolution, as it only provides the local homonuclear correlation information associated with the specific protons selected by the SQ chemical shift frequency. The 3D pulse sequence and its efficiency are demonstrated experimentally on small molecular compounds in the solid state. We expect that this approach would create avenues for further developments by suitably combining the benefits of partial deuteration of samples, selective excitation
The Double-Well Potential in Quantum Mechanics: A Simple, Numerically Exact Formulation
Jelic, V.; Marsiglio, F.
2012-01-01
The double-well potential is arguably one of the most important potentials in quantum mechanics, because the solution contains the notion of a state as a linear superposition of "classical" states, a concept which has become very important in quantum information theory. It is therefore desirable to have solutions to simple double-well potentials…
The Double-Well Potential in Quantum Mechanics: A Simple, Numerically Exact Formulation
Jelic, V.; Marsiglio, F.
2012-01-01
The double-well potential is arguably one of the most important potentials in quantum mechanics, because the solution contains the notion of a state as a linear superposition of "classical" states, a concept which has become very important in quantum information theory. It is therefore desirable to have solutions to simple double-well potentials…
Spin transport properties in double quantum rings connected in series*
Institute of Scientific and Technical Information of China (English)
Du Jian; Wang Suxin; Pan Jianghong
2011-01-01
A new model of metal/semiconductor/metal double-quantum-ring connected in series is proposed and the transport properties in this model are theoretically studied. The results imply that the transmission coefficient shows periodic variations with increasing semiconductor ring size. The effects of the magnetic field and Rashba spin-orbit interaction on the transmission coefficient for two kinds of spin state electrons are different. The number of the transmission coefficient peaks is related to the length ratio between the upper ann and the half circumference of the ring. In addition, the transmission coefficient shows oscillation behavior with enhanced external magnetic field, and the corresponding average value is related to the two leads' relative position.
Quantum Interference in Time-Delayed Nonsequential Double Ionization
Maxwell, A S
2015-01-01
We perform a systematic analysis of quantum interference in nonsequential double ionization focusing on the recollision-excitation with subsequent ionization (RESI) mechanism, employing the strong-field approximation (SFA). We find that interference has a major influence on the shape, localization and symmetry of the correlated electron momentum distributions. In particular, the fourfold symmetry with regard to the parallel momentum components observed in previous SFA studies is broken. Two types of interference are observed and thoroughly analyzed, namely that caused by electron indistinguishability and intra-cycle events, and that stemming from different excitation channels. We find that interference is most prominent around the diagonal and anti-diagonal in the parallel-momentum plane and provide fully analytical expressions for most interference patterns encountered. We also show that this interference can be controlled by an appropriate choice of phase and excited-state geometry. This leads a to myriad o...
Indirect excitons in (111) GaAs double quantum wells
Hubert, C.; Biermann, K.; Hernández-Mínguez, A.; Santos, P. V.
2017-08-01
We study the dynamics of indirect (or dipolar) excitons (interwell IXs) in GaAs (111) double quantum wells (DQWs) subjected to a transverse electric field. In comparison with single (111) QWs, these DQWs can store, for a comparable applied fields and optical excitation density, a density of interwell IXs much larger than in SQWs, thus leading to stronger interwell IX- IX repulsive interactions. We show by means of spatially-resolved optical spectroscopy that interwell IXs in (111) DWQs can be transported over distances exceeding 60 μm. From the spectral dependence of the interwell IX spatial distribution profiles, we show that the long transport distances are due to drift forces arising from the strong interwell IX- IX interactions.
Injection Locking of a Semiconductor Double Quantum Dot Micromaser.
Liu, Y-Y; Stehlik, J; Gullans, M J; Taylor, J M; Petta, J R
2015-11-01
Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models.
Bose condensation of interwell excitons in double quantum wells
Larionov, A V; Ni, P A; Dubonos, S V; Hvam, I; Soerensen, K
2002-01-01
The luminescence of the interwell excitons in the GaAs/AlGaAs double quantum wells, containing large-scale fluctuations of the random potential in the heteroboundary planes, is studied. The properties of the excitons, wherein the excited electron and hole are spatially separated between the neighboring quantum wells by the density and temperature variation within the domain limits of the scale below one micron, are investigated. The interwell excitons by low pumping (below 50 mW) are strongly localized due to the small-scale fluctuations of the random potential. The localized excitons line grows by increase in the resonance excitation capacity through the threshold method. With the temperature growth this line disappears in the spectrum (T sub c <= 3.4 K). The above phenomenon is related to the Bose-Einstein condensation in the quasi-two-dimensional system of the interwell excitons. The critical values of the exciton density and temperature in the studied temperature range (1.5-3.4 K) grow according to the...
Adaptive double chain quantum genetic algorithm for constrained optimization problems
Directory of Open Access Journals (Sweden)
Kong Haipeng
2015-02-01
Full Text Available Optimization problems are often highly constrained and evolutionary algorithms (EAs are effective methods to tackle this kind of problems. To further improve search efficiency and convergence rate of EAs, this paper presents an adaptive double chain quantum genetic algorithm (ADCQGA for solving constrained optimization problems. ADCQGA makes use of double-individuals to represent solutions that are classified as feasible and infeasible solutions. Fitness (or evaluation functions are defined for both types of solutions. Based on the fitness function, three types of step evolution (SE are defined and utilized for judging evolutionary individuals. An adaptive rotation is proposed and used to facilitate updating individuals in different solutions. To further improve the search capability and convergence rate, ADCQGA utilizes an adaptive evolution process (AEP, adaptive mutation and replacement techniques. ADCQGA was first tested on a widely used benchmark function to illustrate the relationship between initial parameter values and the convergence rate/search capability. Then the proposed ADCQGA is successfully applied to solve other twelve benchmark functions and five well-known constrained engineering design problems. Multi-aircraft cooperative target allocation problem is a typical constrained optimization problem and requires efficient methods to tackle. Finally, ADCQGA is successfully applied to solving the target allocation problem.
Adaptive double chain quantum genetic algorithm for constrained optimization problems
Institute of Scientific and Technical Information of China (English)
Kong Haipeng; Li Ni; Shen Yuzhong
2015-01-01
Optimization problems are often highly constrained and evolutionary algorithms (EAs) are effective methods to tackle this kind of problems. To further improve search efficiency and con-vergence rate of EAs, this paper presents an adaptive double chain quantum genetic algorithm (ADCQGA) for solving constrained optimization problems. ADCQGA makes use of double-individuals to represent solutions that are classified as feasible and infeasible solutions. Fitness (or evaluation) functions are defined for both types of solutions. Based on the fitness function, three types of step evolution (SE) are defined and utilized for judging evolutionary individuals. An adaptive rotation is proposed and used to facilitate updating individuals in different solutions. To further improve the search capability and convergence rate, ADCQGA utilizes an adaptive evolution process (AEP), adaptive mutation and replacement techniques. ADCQGA was first tested on a widely used benchmark function to illustrate the relationship between initial parameter values and the convergence rate/search capability. Then the proposed ADCQGA is successfully applied to solve other twelve benchmark functions and five well-known constrained engineering design problems. Multi-aircraft cooperative target allocation problem is a typical constrained optimization problem and requires efficient methods to tackle. Finally, ADCQGA is successfully applied to solving the target allocation problem.
Wei, Hai-Rui; Deng, Fu-Guo
2014-12-18
Quantum logic gates are the key elements in quantum computing. Here we investigate the possibility of achieving a scalable and compact quantum computing based on stationary electron-spin qubits, by using the giant optical circular birefringence induced by quantum-dot spins in double-sided optical microcavities as a result of cavity quantum electrodynamics. We design the compact quantum circuits for implementing universal and deterministic quantum gates for electron-spin systems, including the two-qubit CNOT gate and the three-qubit Toffoli gate. They are compact and economic, and they do not require additional electron-spin qubits. Moreover, our devices have good scalability and are attractive as they both are based on solid-state quantum systems and the qubits are stationary. They are feasible with the current experimental technology, and both high fidelity and high efficiency can be achieved when the ratio of the side leakage to the cavity decay is low.
Directory of Open Access Journals (Sweden)
Boaz Galdino Oliveira
2009-08-01
Full Text Available We have performed a detailed theoretical study in order to understand the charge density topology of the C2H4O···C2H2 and C2H4S···C2H2 heterocyclic hydrogen-bonded complexes. Through the calculations derived from Quantum Theory of Atoms in Molecules (QTAIM, it was observed the formation of hydrogen bonds and secondary interactions. Such analysis was performed through the determination of optimized geometries at B3LYP/6-31G(d,p level of theory, by which is that QTAIM topological operators were computed, such as the electronic density ρ(r, Laplacian Ñ2ρ(r, and ellipticity ε. The examination of the hydrogen bonds has been performed through the measurement of ρ(r, Ñ2ρ(r and ε between (O···H—C and (S···H—C, whereas the secondary interaction between axial hydrogen atoms Hα and carbon of acetylene. In this insight, it was verified the existence of secondary interaction only in C2H4S···C2H2 complex because its structure is propitious to form multiple interactions.
Sayer, Ryan; Maries, Alexandru; Singh, Chandralekha
2017-01-01
Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students' prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in…
Directory of Open Access Journals (Sweden)
Honghao Cai
Full Text Available BACKGROUND AND PURPOSE: Nuclear magnetic resonance (NMR spectroscopy has become an important technique for tissue studies. Since tissues are in semisolid-state, their high-resolution (HR spectra cannot be obtained by conventional NMR spectroscopy. Because of this restriction, extraction and high-resolution magic angle spinning (HR MAS are widely applied for HR NMR spectra of tissues. However, both of the methods are subject to limitations. In this study, the feasibility of HR (1H NMR spectroscopy based on intermolecular multiple-quantum coherence (iMQC technique is explored using fish muscle, fish eggs, and a whole fish as examples. MATERIALS AND METHODS: Intact salmon muscle tissues, intact eggs from shishamo smelt and a whole fish (Siamese algae eater are studied by using conventional 1D one-pulse sequence, Hadamard-encoded iMQC sequence, and HR MAS. RESULTS: When we use the conventional 1D one-pulse sequence, hardly any useful spectral information can be obtained due to the severe field inhomogeneity. By contrast, HR NMR spectra can be obtained in a short period of time by using the Hadamard-encoded iMQC method without shimming. Most signals from fatty acids and small metabolites can be observed. Compared to HR MAS, the iMQC method is non-invasive, but the resolution and the sensitivity of resulting spectra are not as high as those of HR MAS spectra. CONCLUSION: Due to the immunity to field inhomogeneity, the iMQC technique can be a proper supplement to HR MAS, and it provides an alternative for the investigation in cases with field distortions and with samples unsuitable for spinning. The acquisition time of the proposed method is greatly reduced by introduction of the Hadamard-encoded technique, in comparison with that of conventional iMQC method.
Photoluminescence enhancement in double Ge/Si quantum dot structures
Zinovieva, A. F.; Zinovyev, V. A.; Nikiforov, A. I.; Timofeev, V. A.; Mudryi, A. V.; Nenashev, A. V.; Dvurechenskii, A. V.
2016-12-01
Luminescence properties of double Ge/Si quantum dot structures were studied at liquid helium temperature depending on the Si spacer thickness d in QD molecules. A seven-fold increase of the integrated photoluminescence intensity was obtained for the structures with optimal thickness d = 2 nm. This enhancement is explained by increasing the overlap integral of electron and hole wave functions. Two main factors promote this increasing. The first one is that the electrons are localized at the QD base edges and their wave functions are the linear combinations of the states of in-plane Δ valleys, which are perpendicular in k-space to the growth direction [001]. This results in the increasing probability of electron penetration into Ge barriers. The second factor is the arrangement of Ge nanoclusters in closely spaced QD groups. The strong tunnel coupling of QDs within these groups increases the probability of hole finding at the QD base edge, that also promotes the increase of the radiative recombination probability.
Double quantum dot Cooper-pair splitter at finite couplings
Hussein, Robert; Jaurigue, Lina; Governale, Michele; Braggio, Alessandro
2016-12-01
We consider the subgap physics of a hybrid double-quantum dot Cooper-pair splitter with large single-level spacings, in the presence of tunneling between the dots and finite Coulomb intra- and interdot Coulomb repulsion. In the limit of a large superconducting gap, we treat the coupling of the dots to the superconductor exactly. We employ a generalized master-equation method, which easily yields currents, noise, and cross-correlators. In particular, for finite inter- and intradot Coulomb interaction, we investigate how the transport properties are determined by the interplay between local and nonlocal tunneling processes between the superconductor and the dots. We examine the effect of interdot tunneling on the particle-hole symmetry of the currents with and without spin-orbit interaction. We show that spin-orbit interaction in combination with finite Coulomb energy opens the possibility to control the nonlocal entanglement and its symmetry (singlet/triplet). We demonstrate that the generation of nonlocal entanglement can be achieved even without any direct nonlocal coupling to the superconducting lead.
Multiple-path Quantum Interference Effects in a Double-Aharonov-Bohm Interferometer
Directory of Open Access Journals (Sweden)
Yang XF
2010-01-01
Full Text Available Abstract We investigate quantum interference effects in a double-Aharonov-Bohm (AB interferometer consisting of five quantum dots sandwiched between two metallic electrodes in the case of symmetric dot-electrode couplings by the use of the Green’s function equation of motion method. The analytical expression for the linear conductance at zero temperature is derived to interpret numerical results. A three-peak structure in the linear conductance spectrum may evolve into a double-peak structure, and two Fano dips (zero conductance points may appear in the quantum system when the energy levels of quantum dots in arms are not aligned with one another. The AB oscillation for the magnetic flux threading the double-AB interferometer is also investigated in this paper. Our results show the period of AB oscillation can be converted from 2π to π by controlling the difference of the magnetic fluxes threading the two quantum rings.
Manipulative Properties of Asymmetric Double Quantum Dots via Laser and Gate Voltage
Institute of Scientific and Technical Information of China (English)
ZHAO Shun-Cai; LIU Zheng-Dong
2009-01-01
We present a density matrix approach for the theoretical description of an asymmetric double quantum dot (QD) system. The results show that the properties of gain, absorption and dispersion of the double QD system, the population of the state with one hole in one dot and an electron in another dot transferred by tunneling can be manipulated by a laser pulse or gate voltage. Our scheme may demonstrate the possibility of electro-optical manipulation of quantum systems.
Spin-orbit effects in carbon-nanotube double quantum dots
DEFF Research Database (Denmark)
Weiss, S; Rashba, E I; Kuemmeth, Ferdinand;
2010-01-01
We study the energy spectrum of symmetric double quantum dots in narrow-gap carbon nanotubes with one and two electrostatically confined electrons in the presence of spin-orbit and Coulomb interactions. Compared to GaAs quantum dots, the spectrum exhibits a much richer structure because of the sp...
Quantum phase diagram of Polar Molecules in 1D Double Wire Systems
Chang, Chi-Ming; Wang, Daw-Wei
2007-03-01
We study the quantum phase transitions of fermionic polar molecules loaded in a double wire potential. By tuning the magnitude and direction of external electric field we observed many interesting quantum phases in different parameter range, including an easy-plane spin density wave, a triplet superconducting phase, and a truly long range order of easy-axis ferromagnetic phase in strong interacting regime. We also discuss how these exotic quantum phases can be measured in the existing experimental techniques.
Directory of Open Access Journals (Sweden)
Pengqin Shi
2016-09-01
Full Text Available Based on the time-nonlocal particle number-resolved master equation, we investigate the sequential electron transport through the interacting double quantum dots. Our calculations show that there exists the effect of energy renormalization in the dispersion of the bath interaction spectrum and it is sensitive to the the bandwidth of the bath. This effect would strongly affect the stationary current and its zero-frequency shot noise for weak inter-dot coherent coupling strength, but for strong inter-dot coupling regime, it is negligible due to the strong intrinsic Rabi coherent dynamics. Moreover, the possible observable effects of the energy renormalization in the noise spectrum are also investigated through the Rabi coherence signal. Finally, the non-Markovian effect is manifested in the finite-frequency noise spectrum with the appearance of quasisteps, and the magnitude of these quasisteps are modified by the dispersion function.
Shi, Pengqin; Hu, Menghan; Ying, Yaofeng; Jin, Jinshuang
2016-09-01
Based on the time-nonlocal particle number-resolved master equation, we investigate the sequential electron transport through the interacting double quantum dots. Our calculations show that there exists the effect of energy renormalization in the dispersion of the bath interaction spectrum and it is sensitive to the the bandwidth of the bath. This effect would strongly affect the stationary current and its zero-frequency shot noise for weak inter-dot coherent coupling strength, but for strong inter-dot coupling regime, it is negligible due to the strong intrinsic Rabi coherent dynamics. Moreover, the possible observable effects of the energy renormalization in the noise spectrum are also investigated through the Rabi coherence signal. Finally, the non-Markovian effect is manifested in the finite-frequency noise spectrum with the appearance of quasisteps, and the magnitude of these quasisteps are modified by the dispersion function.
Energy Technology Data Exchange (ETDEWEB)
Horsten, H.F. von [Institut fuer Physikalische Chemie, Christian-Albrechts-Universitaet, Olshausenstrasse 40, 24098 Kiel (Germany); Hartke, B. [Institut fuer Physikalische Chemie, Christian-Albrechts-Universitaet, Olshausenstrasse 40, 24098 Kiel (Germany)], E-mail: hartke@phc.uni-kiel.de
2007-09-25
Double proton transfer reactions of pyrazole-guanidine species exhibit unusual energy profiles of a plateau form, different from the standard single and double barrier shapes. We have demonstrated earlier that this leads to a characteristically different quantum dynamical behavior of plateau reactions, when measured appropriately. Here we show that these differences also carry over to traditional measures of reaction probability.
Tunable few-electron double quantum dots with integrated charge read-out
Elzerman, J. M.; Hanson, R.; Greidanus, J. S.; Willems van Beveren, L. H.; De Franceschi, S.; Vandersypen, L. M. K.; Tarucha, S.; Kouwenhoven, L. P.
2004-11-01
We report on the realization of few-electron double quantum dots defined in a two-dimensional electron gas by means of surface gates on top of a GaAs/AlGaAs heterostructure. Two quantum point contacts (QPCs) are placed in the vicinity of the double quantum dot and serve as charge detectors. These enable determination of the number of conduction electrons on each dot. This number can be reduced to zero, while still allowing transport measurements through the double dot. The coupling between the two dots can be controlled even in the few-electron regime. Microwave radiation is used to pump an electron from one dot to the other by absorption of a single photon. The experiments demonstrate that this quantum dot circuit can serve as a good starting point for a scalable spin-qubit system.
A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor
DEFF Research Database (Denmark)
Hu, Yongjie; Churchill, Hugh; Reilly, David
2007-01-01
: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top gate-defined double quantum dot based on Ge/Si heterostructure nanowires with fully tunable coupling between the dots......Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation...... and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to form a solid-state spin...
Tunable double quantum dots in InAs nanowires defined by local gate electrodes.
Fasth, Carina; Fuhrer, Andreas; Samuelson, Lars
2006-03-01
We present low-temperature transport measurements on quantum dots induced in homogeneous InAs quantum wires 50 nm in diameter. Quantum dots are induced by electrical depletion of the wire using local gate electrodes with down to 30 nm electrode spacing. This scheme has permitted the realization of fully gate-defined multiple quantum dots along the nanowire [1]. Tunability in double quantum dots is a prerequisite for the system to be operated as a quantum gate. We demonstrate control over the lead tunnel barrier transparencies and, in the case of double quantum dots, the interdot coupling. Using the local gate electrodes also as plunger gates we measure double dot honeycomb stability diagrams which show the transition from a single large dot to two weakly coupled dots at 4.2K. The induced quantum dots can be tuned into the few-electron regime which is shown from Coulomb blockade measurements. We extract values of orbital energy-level spacings, capacitances and capacitive and tunnel interdot coupling for this system. [1] C. Fasth et al., NanoLett 5, 1487 (2005).
Kubo, T.; Tokura, Y.; Tarucha, S.
2010-01-01
We theoretically investigate spin-dependent electron transport through an Aharonov-Bohm-Casher interferometer containing a laterally coupled double quantum dot. In particular, we numerically calculate the Aharonov-Bohm and Aharonov-Casher oscillations of the linear conductance in the Kondo regime. We show that the AC oscillation in the Kondo regime deviates from the sinusoidal form.
Hu, X; Hu, Xuedong
2000-01-01
We study theoretically a double quantum dot hydrogen molecule in the GaAs conduction band as the basic elementary gate for a quantum computer with the electron spins in the dots serving as qubits. Such a two-dot system provides the necessary two-qubit entanglement required for quantum computation. We determine the excitation spectrum of two horizontally coupled quantum dots with two confined electrons, and study its dependence on an external magnetic field. In particular, we focus on the splitting of the lowest singlet and triplet states, the double occupation probability of the lowest states, and the relative energy scales of these states. We point out that at zero magnetic field it is difficult to have both a vanishing double occupation probability for a small error rate and a sizable exchange coupling for fast gating. On the other hand, finite magnetic fields may provide finite exchange coupling for quantum computer operations with small errors. We critically discuss the applicability of the envelope funct...
Liu, Bao; Zhang, Feng-Yang; Song, Jie; Song, He-Shan
2015-01-01
We propose a direct measurement scheme to read out the geometric phase of a coupled double quantum dot system via a quantum point contact(QPC) device. An effective expression of the geometric phase has been derived, which relates the geometric phase of the double quantum dot qubit to the current through QPC device. All the parameters in our expression are measurable or tunable in experiment. Moreover, since the measurement process affects the state of the qubit slightly, the geometric phase can be protected. The feasibility of the scheme has been analyzed. Further, as an example, we simulate the geometrical phase of a qubit when the QPC device is replaced by a single electron transistor(SET). PMID:26121538
He-, Ne-, and Ar-phosgene intermolecular potential energy surfaces
DEFF Research Database (Denmark)
Munteanu, Cristian R.; Henriksen, Christian; Felker, Peter M.
2013-01-01
Using the CCSD(T) model, we evaluated the intermolecular potential energy surfaces of the He-, Ne-, and Ar-phosgene complexes. We considered a representative number of intermolecular geometries for which we calculated the corresponding interaction energies with the augmented (He complex) and double...
Dissipatively driven entanglement of two nuclear spin ensembles in a double quantum dot
Energy Technology Data Exchange (ETDEWEB)
Schuetz, Martin J.A.; Kessler, Eric M.; Cirac, Juan Ignacio; Giedke, Geza [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany)
2013-07-01
Typically, quantum information schemes have been discussed in the context of isolated many-body systems subject to unitary dynamics. Here, dissipation has been identified as a mechanism that corrupts the useful quantum properties of the system under study. Recently, however, with the advent of novel ideas such as dissipative engineering, a paradigm shift could be observed in quantum physics. More and more approaches actively utilize dissipation as a driving force behind the emergence of coherent quantum phenomena. In this spirit, we propose a transport scheme for an electrically defined double quantum dot in which the two nuclear ensembles in the host environment are actively pumped into an entangled target state. Based on a self-consistent Holstein-Primakoff approximation, we derive an effective quantum master equation for the nuclear spins which features an unique entangled steady state; accordingly, long lasting entanglement is created deterministically. Prospects for the experimental realization of this proposal are briefly discussed.
Tunable few-electron double quantum dots and Klein tunnelling in ultraclean carbon nanotubes.
Steele, G A; Gotz, G; Kouwenhoven, L P
2009-06-01
Quantum dots defined in carbon nanotubes are a platform for both basic scientific studies and research into new device applications. In particular, they have unique properties that make them attractive for studying the coherent properties of single-electron spins. To perform such experiments it is necessary to confine a single electron in a quantum dot with highly tunable barriers, but disorder has prevented tunable nanotube-based quantum-dot devices from reaching the single-electron regime. Here, we use local gate voltages applied to an ultraclean suspended nanotube to confine a single electron in both a single quantum dot and, for the first time, in a tunable double quantum dot. This tunability is limited by a novel type of tunnelling that is analogous to the tunnelling in the Klein paradox of relativistic quantum mechanics.
Layered double hydroxides as carriers for quantum dots@silica nanospheres
Stoica, Georgiana; Castelló Serrano, Iván.; Palomares, Emilio
2013-02-01
Quantum dot-hydrotalcite layered nanoplatforms were successfully prepared following a one-pot synthesis. The process is very fast and a priori delamination of hydrotalcite is not a prerequisite for the intercalation of quantum dots. The novel materials were extensively characterized by X-ray diffraction, thermogravimetry, infrared spectroscopy, transmission electron microscopy, true color fluorescence microscopy, photoluminescence, and nitrogen adsorption. The quantum dot-hydrotalcite nanomaterials display extremely high stability in mimicking physiological media such as saline serum (pH 5.5) and PBS (pH 7.2). Yet, quantum dot release from the solid structure is noted. In order to prevent the leaking of quantum dots we have developed a novel strategy which consists on using tailor made double layered hydrotalcites as protecting shells for quantum dots embedded into silica nanospheres without changing either the materials or the optical properties.
Double-semion topological order from exactly solvable quantum dimer models
Qi, Yang; Gu, Zheng-Cheng; Yao, Hong
2015-10-01
We construct a generalized quantum dimer model on two-dimensional nonbipartite lattices, including the triangular lattice, the star lattice, and the kagome lattice. At the Rokhsar-Kivelson (RK) point, we obtain its exact ground states that are shown to be a fully gapped quantum spin liquid with the double-semion topological order. The ground-state wave function of such a model at the RK point is a superposition of dimer configurations with a nonlocal sign structure determined by counting the number of loops in the transition graph. We explicitly demonstrate the double-semion topological order in the ground states by showing the semionic statistics of monomer excitations. We also discuss possible implications of such double-semion resonating valence bond states to candidate quantum spin-liquid systems discovered experimentally and numerically in the past few years.
Indian Academy of Sciences (India)
Montu K Hazra; Moitrayee Mukherjee; V Ramanathan; Tapas Chakraborty
2012-01-01
Laser-induced fluorescence spectra of a 2:1 complex between 7-azaindole and water, known as `non-reactive dimer’ of the molecule, have been measured in a supersonic jet expansion. The dispersed fluorescence spectrum of the electronic origin band of the complex shows a very large number of low-frequency vibrational features corresponding to different intermolecular modes of the complex in the ground electronic state. Geometries of several possible isomeric structures of the complex and their vibrational frequencies at harmonic approximation were calculated by electronic structure theory method at MP2/6-31G∗∗ level. An excellent agreement is observed between the measured and calculated intermolecular vibrational mode frequencies for the energetically most favoured structure of the complex, where the water molecule is inserted within one of the two N$\\cdots$H-N hydrogen bonds of the 7AI dimer.
Li, Tao; Long, Gui-Lu
2016-08-01
We propose an effective, scalable, hyperparallel photonic quantum computation scheme in which photonic qubits are hyperencoded both in the spatial degrees of freedom (DOF) and the polarization DOF of each photon. The deterministic hyper-controlled-not (hyper-cnot) gate on a two-photon system is attainable with our interesting interface between the polarized photon and the collective spin wave (magnon) of an atomic ensemble embedded in a double-sided optical cavity, and it doubles the operations in the conventional quantum cnot gate. Moreover, we present a compact hyper-cnotN gate on N +1 hyperencoded photons with only two auxiliary cavity-magnon systems, not more, and it can be faithfully constituted with current experimental techniques. Our proposal enables various applications with the hyperencoded photons in quantum computing and quantum networks.
Sum over topologies and double-scaling limit in 2D Lorentzian quantum gravity
Loll, R
2003-01-01
We construct a combined non-perturbative path integral over geometries and topologies for two-dimensional Lorentzian quantum gravity. The Lorentzian structure is used in an essential way to exclude geometries with unacceptably large causality violations. The remaining sum can be performed analytically and possesses a unique and well-defined double-scaling limit, a property which has eluded similar models of Euclidean quantum gravity in the past.
Collective Behavior of a Spin-Aligned Gas of Interwell Excitons in Double Quantum Wells
DEFF Research Database (Denmark)
Larionov, A. V.; Bayer, M.; Hvam, Jørn Märcher;
2005-01-01
The kinetics of a spin-aligned gas of interwell excitons in GaAs/AlGaAs double quantum wells (n–i–n heterostructure) is studied. The temperature dependence of the spin relaxation time for excitons, in which a photoexcited electron and hole are spatially separated between two adjacent quantum wells...... is associated with indirect evidence of the coherence of the collective phase of interwell excitons at temperatures below the critical value....
Electron-nuclear interaction in 13C nanotube double quantum dots
Churchill, Hugh Olen Hill; Bestwick, Andrew J.; Harlow, Jennifer W.; Kuemmeth, Ferdinand; Marcos, David; Stwertka, Carolyn H.; Watson, Susan K.; Marcus, Charles Masamed
2008-01-01
For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource allowing storage and retrieval of quantum information. To investigate the effect of a controllable nuclear environment on the evolution of confined electron spins, we have fabricated and measured gate-defined double quantum dots with integrated charge sensors made from single-walled carbon nanotubes with a variabl...
Thermopower in parallel double quantum dots with Rashba spin-orbit interaction
Institute of Scientific and Technical Information of China (English)
Xue Hui-Jie; Lü Tian-Quan; Zhang Hong-Chen; Yin Hai-Tao; Cui Lian; He Ze-Long
2011-01-01
Based on the Green's function technique and the equation of motion approach, this paper theoretically studies the thermoelectric effect in parallel coupled double quantum dots (DQDs), in which Rashba spin-orbit interaction is taken into account. Rashba spin-orbit interaction contributions, even in a magnetic field, are exhibited obviously in the double quantum dots system for the thermoelectric effect. The periodic oscillation of thermopower can be controlled by tunning the Rashba spin-orbit interaction induced phase. The interesting spin-dependent thermoelectric effects will arise which has important influence on thermoelectric properties of the studied system.
Equations of motion in Double Field Theory: from classical particles to quantum cosmology
Kan, Nahomi; Shiraishi, Kiyoshi
2012-01-01
The equation of motion for a point particle in the background field of double field theory is considered. We find that the motion is described by a geodesic flow in the doubled geometry. Inspired by analysis on the particle motion, we propose a modified model of quantum string cosmology, which includes two scale factors. The report is based on Phys. Rev. D84 (2011) 124049 [arXiv:1108.5795].
Full counting statistics of level renormalization in electron transport through double quantum dots.
Luo, JunYan; Jiao, HuJun; Shen, Yu; Cen, Gang; He, Xiao-Ling; Wang, Changrong
2011-04-13
We examine the full counting statistics of electron transport through double quantum dots coupled in series, with particular attention being paid to the unique features originating from level renormalization. It is clearly illustrated that the energy renormalization gives rise to a dynamic charge blockade mechanism, which eventually results in super-Poissonian noise. Coupling of the double dots to an external heat bath leads to dephasing and relaxation mechanisms, which are demonstrated to suppress the noise in a unique way.
Full counting statistics of level renormalization in electron transport through double quantum dots
Energy Technology Data Exchange (ETDEWEB)
Luo Junyan; Shen Yu; Cen Gang; He Xiaoling; Wang Changrong [School of Science, Zhejiang University of Science and Technology, Hangzhou 310023 (China); Jiao Hujun, E-mail: jyluo@zust.edu.cn [Department of Physics, Shanxi University, Taiyuan, Shanxi 030006 (China)
2011-04-13
We examine the full counting statistics of electron transport through double quantum dots coupled in series, with particular attention being paid to the unique features originating from level renormalization. It is clearly illustrated that the energy renormalization gives rise to a dynamic charge blockade mechanism, which eventually results in super-Poissonian noise. Coupling of the double dots to an external heat bath leads to dephasing and relaxation mechanisms, which are demonstrated to suppress the noise in a unique way.
Charge Dynamics and Spin Blockade in a Hybrid Double Quantum Dot in Silicon
Directory of Open Access Journals (Sweden)
Matias Urdampilleta
2015-08-01
Full Text Available Electron spin qubits in silicon, whether in quantum dots or in donor atoms, have long been considered attractive qubits for the implementation of a quantum computer because of silicon’s “semiconductor vacuum” character and its compatibility with the microelectronics industry. While donor electron spins in silicon provide extremely long coherence times and access to the nuclear spin via the hyperfine interaction, quantum dots have the complementary advantages of fast electrical operations, tunability, and scalability. Here, we present an approach to a novel hybrid double quantum dot by coupling a donor to a lithographically patterned artificial atom. Using gate-based rf reflectometry, we probe the charge stability of this double quantum-dot system and the variation of quantum capacitance at the interdot charge transition. Using microwave spectroscopy, we find a tunnel coupling of 2.7 GHz and characterize the charge dynamics, which reveals a charge T_{2}^{*} of 200 ps and a relaxation time T_{1} of 100 ns. Additionally, we demonstrate a spin blockade at the inderdot transition, opening up the possibility to operate this coupled system as a singlet-triplet qubit or to transfer a coherent spin state between the quantum dot and the donor electron and nucleus.
Quantum dynamics of a particle interacting with a double barrier
Energy Technology Data Exchange (ETDEWEB)
Cacciari, Ilaria [Istituto di Fisica Applicata ' Nello Carrara' del Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy); Lantieri, Marco [Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche, Sezione di Firenze, via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy); Moretti, Paolo [Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche, Sezione di Firenze, via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze (Italy)
2007-10-12
Following a previously developed method, the problem of a particle scattered by a double barrier is studied. Instead of the simple transmission or reflection, the more difficult case of the arrival in the region between the barriers is considered and solved explicitly by using matrix methods.
Directory of Open Access Journals (Sweden)
Ryan Sayer
2017-05-01
Full Text Available Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students’ prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in various situations that appear to be counterintuitive and contradict classical notions of particles and waves. For example, if we send single electrons through the slits, they may behave as a “wave” in part of the experiment and as a “particle” in another part of the same experiment. Here we discuss the development and evaluation of a research-validated Quantum Interactive Learning Tutorial (QuILT which makes use of an interactive simulation to improve student understanding of the double-slit experiment and strives to help students develop a good grasp of foundational issues in quantum mechanics. We discuss common student difficulties identified during the development and evaluation of the QuILT and analyze the data from the pretest and post test administered to the upper-level undergraduate and first-year physics graduate students before and after they worked on the QuILT to assess its effectiveness. These data suggest that on average, the QuILT was effective in helping students develop a more robust understanding of foundational concepts in quantum mechanics that defy classical intuition using the context of the double-slit experiment. Moreover, upper-level undergraduates outperformed physics graduate students on the post test. One possible reason for this difference in performance may be the level of student engagement with the QuILT due to the grade incentive. In the undergraduate course, the post test was graded for correctness while in the graduate course, it was only graded for completeness.
A New Type of Photoelectric Response in a Double Barrier Structure with a Wide Quantum Well
Institute of Scientific and Technical Information of China (English)
ZHOU Xia; ZHENG Hou-Zhi
2005-01-01
@@ We have calculated the photoelectric response in a specially designed double barrier structure. It has been verified that a transfer of the internal photovoltaic effect in the quantum well to the tunnelling transport through above-barrier quasibound states of the emitter barrier may give rise to a remarkable photocurrent.
Collective Behavior of Interwell Excitons in GaAs/AlGaAs Double Quantum Wells
DEFF Research Database (Denmark)
Larionov, A. V.; Timofeev, V. B.; Hvam, Jørn Märcher;
2000-01-01
Photoluminescence spectra of interwell excitons in double GaAs/AlGaAs quantum wells (n-i-n structures) have been investigated (an interwell excition in these systems is an electron-hole pair spatially separated by a narrow AlAs barrier). Under resonance excitation by circular polarized light, the...
A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor
DEFF Research Database (Denmark)
Hu, Yongjie; Churchill, Hugh; Reilly, David;
2007-01-01
Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitati...
Relaxation and Dephasing in a Two-Electron 13C Nanotube Double Quantum Dot
DEFF Research Database (Denmark)
Churchill, H O H; Kuemmeth, Ferdinand; Harlow, J W;
2009-01-01
We use charge sensing of Pauli blockade (including spin and isospin) in a two-electron 13C nanotube double quantum dot to measure relaxation and dephasing times. The relaxation time T1 first decreases with a parallel magnetic field and then goes through a minimum in a field of 1.4 T. We attribute...
Closed form solution for a double quantum well using Gr\\"obner basis
Acus, A
2011-01-01
Analytical expressions for spectrum, eigenfunctions and dipole matrix elements of a square double quantum well (DQW) are presented for a general case when the potential in different regions of the DQW has different heights and effective masses are different. This was achieved by Gr\\"obner basis algorithm which allows to disentangle the resulting coupled polynomials without explicitly solving the transcendental eigenvalue equation.
Bonora, Marco; Becker, James; Saxena, Sunil
2004-10-01
We show the use of the observer blind spots effect for the elimination of electron spin-echo envelope modulation (ESEEM) peaks in double quantum coherence (DQC) electron spin resonance (ESR). The suppression of ESEEM facilitates the routine and unambiguous extraction of distances from DQC-ESR spectra. This is also the first demonstration of this challenging methodology on commercial instrumentation.
Optical analogue of 2D heteronuclear double-quantum NMR
Tollerud, Jonathan
2016-01-01
Heteronuclear multi-quantum spectroscopy is a powerful part of the NMR toolbox, commonly used to identify specific sequences of atoms in complex pulse sequences designed to determine the structure of complex molecules, including proteins. Optical coherent multidimensional spectroscopy (CMDS) is analogous to multidimensional NMR and many of the techniques of NMR have been adapted for application in the optical regime. This has been highly successful, with CMDS being used to understand energy transfer in photosynthesis and many body effects in semiconductor nanostructures amongst many other scientific breakthroughs. Experimental challenges have, however, prevented the translation of heteronuclear multi-quantum NMR to the optical regime, where capabilities to isolate signals in otherwise congested spectra, reduce acquisition times and enable more incisive probes of multi-particle correlations and complex electronic systems would have great benefit. Here we utilise a diffraction based pulseshaper to impose the tw...
Intermolecular and surface forces
Israelachvili, Jacob N
2011-01-01
This reference describes the role of various intermolecular and interparticle forces in determining the properties of simple systems such as gases, liquids and solids, with a special focus on more complex colloidal, polymeric and biological systems. The book provides a thorough foundation in theories and concepts of intermolecular forces, allowing researchers and students to recognize which forces are important in any particular system, as well as how to control these forces. This third edition is expanded into three sections and contains five new chapters over the previous edition.· starts fr
Deterministic entanglement distillation for secure double-server blind quantum computation
Sheng, Yu-Bo; Zhou, Lan
2015-01-01
Blind quantum computation (BQC) provides an efficient method for the client who does not have enough sophisticated technology and knowledge to perform universal quantum computation. The single-server BQC protocol requires the client to have some minimum quantum ability, while the double-server BQC protocol makes the client's device completely classical, resorting to the pure and clean Bell state shared by two servers. Here, we provide a deterministic entanglement distillation protocol in a practical noisy environment for the double-server BQC protocol. This protocol can get the pure maximally entangled Bell state. The success probability can reach 100% in principle. The distilled maximally entangled states can be remaind to perform the BQC protocol subsequently. The parties who perform the distillation protocol do not need to exchange the classical information and they learn nothing from the client. It makes this protocol unconditionally secure and suitable for the future BQC protocol. PMID:25588565
Deterministic entanglement distillation for secure double-server blind quantum computation.
Sheng, Yu-Bo; Zhou, Lan
2015-01-15
Blind quantum computation (BQC) provides an efficient method for the client who does not have enough sophisticated technology and knowledge to perform universal quantum computation. The single-server BQC protocol requires the client to have some minimum quantum ability, while the double-server BQC protocol makes the client's device completely classical, resorting to the pure and clean Bell state shared by two servers. Here, we provide a deterministic entanglement distillation protocol in a practical noisy environment for the double-server BQC protocol. This protocol can get the pure maximally entangled Bell state. The success probability can reach 100% in principle. The distilled maximally entangled states can be remaind to perform the BQC protocol subsequently. The parties who perform the distillation protocol do not need to exchange the classical information and they learn nothing from the client. It makes this protocol unconditionally secure and suitable for the future BQC protocol.
Four-Electron Systems in a Coupled Double-Layer Quantum Dots
Institute of Scientific and Technical Information of China (English)
XIE Wen-Fang
2003-01-01
Making use of the method of few-body physics, the energy spectrum of a four-electron system consisting in a vertically coupled double-layer quantum dot as a function of the strength ofa magnetic field is investigated. Discontinuous ground-state transitions induced by an external magnetic field are shown. We find that, in the strong coupling case, the ground-state transitions depend not only on the external magnetic field B but also on the distance d between double-layer quantum dots. However, in the case of weak coupling, the ground-state transitions occur in the new sequence of the values of the magic angular momentum. Hence, the interlayer separation d and electron-electron interaction strongly affect the ground state of the coupled quantum dots.
Gravitational Waves detection and spectroscopy with a Double-slit Quantum Eraser
de Matos, Clovis Jacinto; Armengol, Josep Maria Perdigues
2008-01-01
The interaction between a gravitational wave (GW) and entangled photons in the Walborn's "which-way experiment" on a double-slit quantum eraser is investigated. GWs change the polarization states in an entangled pair introducing decoherence and changing the experimental condition of the double slit quantum eraser. By varying the path of one of the entangled photons one can tune the GW detector to a certain specific wavelength, obtaining, in principle, the profile of the GW spectrum. The presence of GWs can be revealed by searching for entangled photon coincidences in the dark fringes of the recovered interference pattern of the quantum eraser, with the key advantage of discriminating the dark noise counts from the real counts due to photons deviated by the GW with heralded photon techniques. Alternatively, the incomplete destruction of the interference patterns may reveal the interaction of GWs with the photon's polarization. We propose this gedankenexperiment as an improvement to the already existing detecti...
Magnetic Anticrossing of 1D Subbands in Coupled Ballistic Double Quantum Wires
Energy Technology Data Exchange (ETDEWEB)
BLOUNT,MARK A.; MOON,JEONG-SUN; SIMMONS,JERRY A.; LYO,SUNGKWUN K.; WENDT,JOEL R.; RENO,JOHN L.
2000-07-13
We study the low-temperature in-plane magnetoconductance of vertically coupled double quantum wires. Using a novel flip-chip technique, the wires are defined by two pairs of mutually aligned split gates on opposite sides of a s 1 micron thick AlGaAs/GaAs double quantum well heterostructure. We observe quantized conductance steps due to each quantum well and demonstrate independent control of each ID wire. A broad dip in the magnetoconductance at -6 T is observed when a magnetic field is applied perpendicular to both the current and growth directions. This conductance dip is observed only when 1D subbands are populated in both the top and bottom constrictions. This data is consistent with a counting model whereby the number of subbands crossing the Fermi level changes with field due to the formation of an anticrossing in each pair of 1D subbands.
Double-slit experiment with single wave-driven particles and its relation to quantum mechanics
DEFF Research Database (Denmark)
Andersen, Anders Peter; Madsen, Jacob; Reichelt, Christian Günther
2015-01-01
even though it is possible to determine unambiguously which slit the walking droplet passes. Here we argue, however, that the single-particle statistics in such an experiment will be fundamentally different from the single-particle statistics of quantum mechanics. Quantum mechanical interference takes...... place between different classical paths with precise amplitude and phase relations. In the double-slit experiment with walking droplets, these relations are lost since one of the paths is singled out by the droplet. To support our conclusions, we have carried out our own double-slit experiment, and our...... results, in particular the long and variable slit passage times of the droplets, cast strong doubt on the feasibility of the interference claimed by Couder and Fort. To understand theoretically the limitations of wave-driven particle systems as analogs to quantum mechanics, we introduce a Schro...
Hyperfine and spin-orbit dynamics in GaAs double quantum dots
Shulman, Michael; Nichol, John; Harvey, Shannon; Pal, Arijeet; Halperin, Bertrand; Umansky, Vladimir; Yacoby, Amir
2015-03-01
Semiconductor quantum dots provide a unique platform for single-particle physics and many-body quantum mechanics. In particular, understanding the dynamics of a single electron interacting with a nuclear spin bath is key to improving spin-based quantum information processing, since the hyperfine interaction limits the performance of many spin qubits. We probe the electron-nuclear interaction by measuring the splitting at the anti-crossing between the electron singlet (S) and m =1 triplet (T +) states in a GaAs double quantum dot. Using Landau-Zener sweeps, we find that the size of this splitting varies by more than an order of magnitude depending on the magnitude and direction of the external magnetic field. These results are consistent with a competition between the spin orbit interaction and the hyperfine interaction, even though the extracted spin orbit length is much larger than the size of the double quantum dot. We confirm these results by using Landau-Zener sweeps to measure the high-frequency correlations in the S-T + splitting that arise from the Larmor precession of the nuclei. These unexpected results have implications for improving the performance of spin-based quantum information processing, as well as improving our understanding of the central spin problem.
Double-slit experiment with single wave-driven particles and its relation to quantum mechanics.
Andersen, Anders; Madsen, Jacob; Reichelt, Christian; Rosenlund Ahl, Sonja; Lautrup, Benny; Ellegaard, Clive; Levinsen, Mogens T; Bohr, Tomas
2015-07-01
In a thought-provoking paper, Couder and Fort [Phys. Rev. Lett. 97, 154101 (2006)] describe a version of the famous double-slit experiment performed with droplets bouncing on a vertically vibrated fluid surface. In the experiment, an interference pattern in the single-particle statistics is found even though it is possible to determine unambiguously which slit the walking droplet passes. Here we argue, however, that the single-particle statistics in such an experiment will be fundamentally different from the single-particle statistics of quantum mechanics. Quantum mechanical interference takes place between different classical paths with precise amplitude and phase relations. In the double-slit experiment with walking droplets, these relations are lost since one of the paths is singled out by the droplet. To support our conclusions, we have carried out our own double-slit experiment, and our results, in particular the long and variable slit passage times of the droplets, cast strong doubt on the feasibility of the interference claimed by Couder and Fort. To understand theoretically the limitations of wave-driven particle systems as analogs to quantum mechanics, we introduce a Schrödinger equation with a source term originating from a localized particle that generates a wave while being simultaneously guided by it. We show that the ensuing particle-wave dynamics can capture some characteristics of quantum mechanics such as orbital quantization. However, the particle-wave dynamics can not reproduce quantum mechanics in general, and we show that the single-particle statistics for our model in a double-slit experiment with an additional splitter plate differs qualitatively from that of quantum mechanics.
Double-slit and electromagnetic models to complete quantum mechanics
De Luca, Jayme
2010-01-01
We analyze a realistic microscopic model for electronic scattering based on the neutral-delay-equations for point charges of the Wheeler-Feynman electrodynamics. We propose a microscopic model according to the electrodynamics of point-charges, complex enough to describe the essential physics. Our microscopic model reaches a simple qualitative agreement with the experimental results as regards interference in double-slit scattering and in electronic scattering by crystals. We discuss our model in the light of existing experimental results, including a qualitative disagreement found for the double-slit experiment. We discuss an approximation for the complex neutral-delay dynamics of our model using piecewise-defined (discontinuous) velocities for all charges and piecewise-constant-velocities for the scattered charge. Our approximation predicts the De Broglie wavelength as an inverse function of the incoming velocity and in the correct order of magnitude. We explain the scattering by crystals in the light of the...
States of an on-axis two-hydrogenic-impurity complex in concentric double quantum rings
Energy Technology Data Exchange (ETDEWEB)
R-Fulla, M., E-mail: marlonfulla@yahoo.com [Escuela de Física, Universidad Nacional de Colombia, A.A. 3840, Medellín (Colombia); Institución Universitaria Pascual Bravo, A.A. 6564, Medellín (Colombia); Marín, J.H.; Suaza, Y.A. [Escuela de Física, Universidad Nacional de Colombia, A.A. 3840, Medellín (Colombia); Duque, C.A. [Grupo de Materia Condensada-U de A, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia, calle 70 No. 52-21, Medellín (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico)
2014-06-13
The energy structure of an on-axis two-donor system (D{sub 2}{sup 0}) confined in GaAs concentric double quantum rings under the presence of magnetic field and hydrostatic pressure was analyzed. Based on structural data for the double quantum ring morphology, a rigorous adiabatic procedure was implemented to separate the electrons' rapid in-plane motions from the slow rotational ones. A one-dimensional equation with an effective angular-dependent potential, which describes the two-electron rotations around the common symmetry axis of quantum rings was obtained. It was shown that D{sub 2}{sup 0} complex characteristic features are strongly dependent on the quantum ring geometrical parameters. Besides, by changing the hydrostatic pressure and magnetic field strengths, it is possible to tune the D{sub 2}{sup 0} energy structure. Our results are comparable to those previously reported for a single and negative ionized donor in a spherical quantum dot after a selective setting of the geometrical parameters of the structure. - Highlights: • We report the eigenenergies of a D{sub 2}{sup 0} complex in concentric double quantum rings. • Our model is versatile enough to analyze the dissociation process D{sub 2}{sup 0}→D{sup 0}+D{sup +}+e{sup −}. • We compare the D{sup 0} eigenenergies in horn toroidal and spherical shaped quantum dots. • We show the effects of hydrostatic pressure and magnetic field on the D{sub 2}{sup 0} spectrum. • The use of hydrostatic pressure provides higher thermal stability to the D{sub 2}{sup 0} complex.
Brovarets', Ol'ha O; Yurenko, Yevgen P; Hovorun, Dmytro M
2014-01-01
This study aims to cast light on the physico-chemical nature and energetic of the non-conventional CH···O/N H-bonds in the biologically important natural nucleobase pairs using a comprehensive quantum-chemical approach. As a whole, the 36 biologically important pairs, involving canonical and rare tautomers of nucleobases, were studied by means of all available up-to-date state-of-the-art quantum-chemical techniques along with quantum theory "Atoms in molecules" (QTAIM), Natural Bond Orbital (NBO) analysis, Grunenberg's compliance constants theory, geometrical and vibrational analyses to identify the CH···O/N interactions, reveal their physico-chemical nature and estimate their strengths as well as contribution to the overall base-pairs stability. It was shown that all the 38 CH···O/N contacts (25 CH···O and 13 CH···N H-bonds) completely satisfy all classical geometrical, electron-topological, in particular Bader's and "two-molecule" Koch and Popelier's, and vibrational criteria of H-bonding. The positive values of Grunenberg's compliance constants prove that the CH···O/N contacts in nucleobase pairs are stabilizing interactions unlike electrostatic repulsion and anti-H-bonds. NBO analysis indicates the electron density transfer from the lone electron pair of the acceptor atom (O/N) to the antibonding orbital corresponding to the donor group σ(∗)(CH). Moreover, significant increase in the frequency of the out-of-plane deformation modes γ (CH) under the formation of the CH···O (by 17.2÷81.3/10.8÷84.7 cm(-1)) and CH···N (by 32.7÷85.9/9.0÷77.9 cm(-1)) H-bonds at the density functional theory (DFT)/second-order Møller-Plesset (MP2) levels of theory, respectively, and concomitant changes of their intensities can be considered as reliable indicators of H-bonding. The strengths of the CH···O/N interactions, evaluated by means of Espinosa-Molins-Lecomte formula, lie within the range 0.45÷3.89/0.62÷4.10 kcal/mol for the CH
Protsenko, V. S.; Katanin, A. A.
2017-06-01
We explore the effects of asymmetry of hopping parameters between double parallel quantum dots and the leads on the conductance and a possibility of local magnetic moment formation in this system using functional renormalization group approach with the counterterm. We demonstrate a possibility of a quantum phase transition to a local moment regime [so-called singular Fermi liquid (SFL) state] for various types of hopping asymmetries and discuss respective gate voltage dependencies of the conductance. We show that, depending on the type of the asymmetry, the system can demonstrate either a first-order quantum phase transition to an SFL state, accompanied by a discontinuous change of the conductance, similarly to the symmetric case, or the second-order quantum phase transition, in which the conductance is continuous and exhibits Fano-type asymmetric resonance near the transition point. A semianalytical explanation of these different types of conductance behavior is presented.
Cavity-photon-switched coherent transient transport in a double quantum waveguide
Energy Technology Data Exchange (ETDEWEB)
Abdullah, Nzar Rauf, E-mail: nra1@hi.is; Gudmundsson, Vidar, E-mail: vidar@raunvis.hi.is [Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik (Iceland); Tang, Chi-Shung [Department of Mechanical Engineering, National United University, 1, Lienda, 36003 Miaoli, Taiwan (China); Manolescu, Andrei [School of Science and Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik (Iceland)
2014-12-21
We study a cavity-photon-switched coherent electron transport in a symmetric double quantum waveguide. The waveguide system is weakly connected to two electron reservoirs, but strongly coupled to a single quantized photon cavity mode. A coupling window is placed between the waveguides to allow electron interference or inter-waveguide transport. The transient electron transport in the system is investigated using a quantum master equation. We present a cavity-photon tunable semiconductor quantum waveguide implementation of an inverter quantum gate, in which the output of the waveguide system may be selected via the selection of an appropriate photon number or “photon frequency” of the cavity. In addition, the importance of the photon polarization in the cavity, that is, either parallel or perpendicular to the direction of electron propagation in the waveguide system is demonstrated.
Energy Technology Data Exchange (ETDEWEB)
Curilef, S [Departamento de Fisica, Universidad Catolica del Norte, Antofagasta (Chile); Zander, C [Physics Department, University of Pretoria, Pretoria 0002 (South Africa); Plastino, A R [Physics Department, University of Pretoria, Pretoria 0002 (South Africa)
2006-09-01
The connection between entanglement and the speed of quantum evolution (as measured by the time needed to reach an orthogonal state) is discussed in the case of two quantum particles moving in a one-dimensional double well. The aforementioned connection offers an interesting opportunity of discussing the basic features of quantum entanglement within an elementary context, using concepts and methods usually included in university courses of quantum mechanics.
A Remark on CFT Realization of Quantum Doubles of Subfactors. Case Index < 4
Bischoff, Marcel
2015-01-01
It is well-known that the quantum double $D(N\\subset M)$ of a finite depth subfactor $N\\subset M$, or equivalently the Drinfeld center of the even part fusion category, is a unitary modular tensor category. Thus should arise in conformal field theory. We show that for every subfactor $N\\subset M$ with index $[M:N]<4$ the quantum double $D(N\\subset M)$ is realized as the representation category of a completely rational conformal net. In particular, the quantum double of $E_6$ can be realized as a $\\mathbb Z_2$-simple current extension of $\\mathrm{SU}(2)_{10}\\times \\mathrm{Spin}(11)_1$ and thus is not exotic in any sense. As a byproduct we obtain a vertex operator algebra for every such subfactor. We obtain the result by showing that if a subfactor $N\\subset M $ arises from $\\alpha$-induction of completely rational nets $\\mathcal A\\subset \\mathcal B$ and there is a net $\\tilde{\\mathcal A}$ with the opposite braiding, then the quantum $D(N\\subset M)$ is realized by completely rational net. We construct comple...
Crippa, Alessandro; Maurand, Romain; Kotekar-Patil, Dharmraj; Corna, Andrea; Bohuslavskyi, Heorhii; Orlov, Alexei O; Fay, Patrick; Laviéville, Romain; Barraud, Sylvain; Vinet, Maud; Sanquer, Marc; De Franceschi, Silvano; Jehl, Xavier
2017-02-08
We report on dual-gate reflectometry in a metal-oxide-semiconductor double-gate silicon transistor operating at low temperature as a double quantum dot device. The reflectometry setup consists of two radio frequency resonators respectively connected to the two gate electrodes. By simultaneously measuring their dispersive responses, we obtain the complete charge stability diagram of the device. Electron transitions between the two quantum dots and between each quantum dot and either the source or the drain contact are detected through phase shifts in the reflected radio frequency signals. At finite bias, reflectometry allows probing charge transitions to excited quantum-dot states, thereby enabling direct access to the energy level spectra of the quantum dots. Interestingly, we find that in the presence of electron transport across the two dots the reflectometry signatures of interdot transitions display a dip-peak structure containing quantitative information on the charge relaxation rates in the double quantum dot.
Quantum frequency doubling based on tripartite entanglement with cavities
Juan, Guo; Zhi-Feng, Wei; Su-Ying, Zhang
2016-02-01
We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cavities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the transmission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network. Project supported by the National Natural Science Foundation of China (Grant No. 91430109), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111401110004), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011005-3).
Özdemir, Namık
2013-01-01
The intramolecular thione-thiol tautomerism and intermolecular double proton transfer reaction of the hydrogen-bonded thione and thiol dimers in the title triazole compound were studied at the B3LYP level of theory using 6-311++G(d,p) basis function. The influence of the solvent on the single and double proton transfer reactions was examined in three solvents (chloroform, methanol and water) using the polarizable continuum model (PCM) approximation. The computational results show that the thione tautomer is the most stable isomer with a very high tautomeric energy barrier both in the gas phase and in solution phase, indicating a quite disfavored process. The solvent effect is found to be sizable with increasing polarity. In the double proton transfer reaction, the thione dimer is found to be more stable than thiol dimer both in the gas phase and in solution phase. The energetic and thermodynamic parameters of the double proton transfer process show that the double proton exchange from thione dimer to thiol dimer is thermodynamically unfavored. However, the exchange from thiol dimer to thione dimer for the gas phase and water phase seems to be feasible with a low barrier height and with a negative value in enthalpy and free energy changes. In addition, the hydrogen bonding interactions were analyzed in the gas phase regarding their geometries and energies. It is found that all complex formations are enthalpically favored, and the stability of the H-bonds comes in the order of S1-H2···N2>N2-H2···S1>N3-H3B···O1. Finally, non-linear optical properties were carried out at the same calculation level in the gas phase.
Anisotropic Pauli Spin Blockade of Holes in a GaAs Double Quantum Dot.
Wang, Daisy Q; Klochan, Oleh; Hung, Jo-Tzu; Culcer, Dimitrie; Farrer, Ian; Ritchie, David A; Hamilton, Alex R
2016-12-14
Electrically defined semiconductor quantum dots are attractive systems for spin manipulation and quantum information processing. Heavy-holes in both Si and GaAs are promising candidates for all-electrical spin manipulation, owing to the weak hyperfine interaction and strong spin-orbit interaction. However, it has only recently become possible to make stable quantum dots in these systems, mainly due to difficulties in device fabrication and stability. Here, we present electrical transport measurements on holes in a gate-defined double quantum dot in a GaAs/AlxGa1-xAs heterostructure. We observe clear Pauli spin blockade and demonstrate that the lifting of this spin blockade by an external magnetic field is highly anisotropic. Numerical calculations of heavy-hole transport through a double quantum dot in the presence of strong spin-orbit coupling show quantitative agreement with experimental results and suggest that the observed anisotropy can be explained by both the anisotropic effective hole g-factor and the surface Dresselhaus spin-orbit interaction.
Sisyphus Thermalization of Photons in a Cavity-Coupled Double Quantum Dot
Gullans, M. J.; Stehlik, J.; Liu, Y.-Y.; Eichler, C.; Petta, J. R.; Taylor, J. M.
2016-01-01
We investigate the non-classical states of light that emerge in a microwave resonator coupled to a periodically-driven electron in a nanowire double quantum dot (DQD). Under certain drive configurations, we find that the resonator approaches a thermal state at the temperature of the surrounding substrate with a chemical potential given by a harmonic of the drive frequency. Away from these thermal regions we find regions of gain and loss, where the system can lase, or regions where the DQD acts as a single-photon source. These effects are observable in current devices and have broad utility for quantum optics with microwave photons. PMID:27517784
Institute of Scientific and Technical Information of China (English)
DONG; Zhengchao; FU; Hao
2004-01-01
Taking into account the effects of quantum interference and interface scattering, combining the electron current with hole current contribution to tunnel current,we study the coherent quantum transport in normal-metal/d-wave superconductor/normal-metal (NM/d-wave SC/NM) double tunnel junctions by using extended Blonder-Tinkham-Klapwijk (BTK) approach. It is shown that all quasiparticle transport coefficients and conductance spectrum exhibit oscillating behavior with the energy, in which periodic vanishing of Andreev reflection (AR) above superconducting gap is found.In tunnel limit for the interface scattering strength taken very large, there are a series of bound states of quasiparticles formed in SC.
Fluctuation theorem for a double quantum dot coupled to a point-contact electrometer
Energy Technology Data Exchange (ETDEWEB)
Golubev, D. [Institut für Nanotechnologie, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Utsumi, Y. [Department of Physics Engineering, Faculty of Engineering, Mie University, Tsu, Mie, 514-8507 (Japan); Marthaler, M. [Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Schön, G. [Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, 76128 Karlsruhe, Germany and Institut für Nanotechnologie, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany)
2013-12-04
Motivated by recent experiments on the real-time single-electron counting through a semiconductor GaAs double quantum dot (DQD) by a nearby quantum point contact (QPC), we develop the full-counting statistics of coupled DQD and QPC system. By utilizing the time-scale separation between the dynamics of DQD and QPC, we derive the modified master equation with tunneling rates depending on the counting fields, which fulfill the detailed fluctuation theorem. Furthermore, we derive universal relations between the non-linear corrections to the current and noise, which can be verified in experiments.
Asymmetric Quantum Transport in a Double-Stranded Kronig-Penney Model
Cheon, Taksu; Poghosyan, Sergey S.
2015-06-01
We introduce a double-stranded Kronig-Penney model and analyze its transport properties. Asymmetric fluxes between two strands with suddenly alternating localization patterns are found as the energy is varied. The zero-size limit of the internal lines connecting two strands is examined using quantum graph vertices with four edges. We also consider a two-dimensional Kronig-Penney lattice with two types of alternating layer with δ and δ' connections, and show the existence of energy bands in which the quantum flux can flow only in selected directions.
Negative Differential Resistance Probe for Interdot Interactions in a Double Quantum Dot Array.
Pozner, Roni; Lifshitz, Efrat; Peskin, Uri
2015-05-07
Colloidal quantum dots are free-standing nanostructures with chemically tunable electronic properties. In this work, we consider a new STM tip-double quantum dot (DQD)-surface setup with a unique connectivity, in which the tip is coupled to a single dot and the coupling to the surface is shared by both dots. Our theoretical analysis reveals a unique negative differential resistance (NDR) effect attributed to destructive interference during charge transfer from the DQD to the surface. This NDR can be used as a sensitive probe for interdot interactions in DQD arrays.
Charge transport-induced recoil and dissociation in double quantum dots.
Pozner, Roni; Lifshitz, Efrat; Peskin, Uri
2014-11-12
Colloidal quantum dots (CQDs) are free-standing nanostructures with chemically tunable electronic properties. This combination of properties offers intriguing new possibilities for nanoelectromechanical devices that were not explored yet. In this work, we consider a new scanning tunneling microscopy setup for measuring ligand-mediated effective interdot forces and for inducing motion of individual CQDs within an array. Theoretical analysis of a double quantum dot structure within this setup reveals for the first time voltage-induced interdot recoil and dissociation with pronounced changes in the current. Considering realistic microscopic parameters, our approach enables correlating the onset of mechanical motion under bias voltage with the effective ligand-mediated binding forces.
Vibrational effects in charge transport through a molecular double quantum dot
Sowa, Jakub K; Briggs, G Andrew D; Gauger, Erik M
2016-01-01
Recent progress in the field of molecular electronics has revealed the fundamental importance of the coupling between the electronic degrees of freedom and specific vibrational modes. Considering the examples of a molecular dimer and a carbon nanotube double quantum dot, we here theoretically investigate transport through a two-site system that is strongly coupled to a single vibrational mode. Using a quantum master equation approach, we demonstrate that, depending on the relative positions of the two dots, electron-phonon interactions can lead to negative differential conductance and suppression of the current through the system. We also discuss the experimental relevance of the presented results and possible implementations of the studied system.
Agarwal, Parag; Bee, Saba; Gupta, Archana; Tandon, Poonam; Rastogi, V K; Mishra, Soni; Rawat, Poonam
2014-01-01
FT-IR (4000-400 cm(-1)) and FT-Raman (4000-200 cm(-1)) spectral measurements on solid 2,6-dichlorobenzonitrile (2,6-DCBN) have been done. The molecular geometry, harmonic vibrational frequencies and bonding features in the ground state have been calculated by density functional theory at the B3LYP/6-311++G (d,p) level. A comparison between the calculated and the experimental results covering the molecular structure has been made. The assignments of the fundamental vibrational modes have been done on the basis of the potential energy distribution (PED). To investigate the influence of intermolecular hydrogen bonding on the geometry, the charge distribution and the vibrational spectrum of 2,6-DCBN; calculations have been done for the monomer as well as the tetramer. The intermolecular interaction energies corrected for basis set superposition error (BSSE) have been calculated using counterpoise method. Based on these results, the correlations between the vibrational modes and the structure of the tetramer have been discussed. Molecular electrostatic potential (MEP) contour map has been plotted in order to predict how different geometries could interact. The Natural Bond Orbital (NBO) analysis has been done for the chemical interpretation of hyperconjugative interactions and electron density transfer between occupied (bonding or lone pair) orbitals to unoccupied (antibonding or Rydberg) orbitals. UV spectrum was measured in methanol solution. The energies and oscillator strengths were calculated by Time Dependent Density Functional Theory (TD-DFT) and matched to the experimental findings. TD-DFT method has also been used for theoretically studying the hydrogen bonding dynamics by monitoring the spectral shifts of some characteristic vibrational modes involved in the formation of hydrogen bonds in the ground and the first excited state. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge independent atomic orbital
Feng, Zimin; Sun, Qing-feng; Wan, Langhui; Guo, Hong
2011-10-19
We report the development and an application of a symbolic tool, called SymGF, for analytical derivations of quantum transport properties using the Keldysh nonequilibrium Green's function (NEGF) formalism. The inputs to SymGF are the device Hamiltonian in the second quantized form, the commutation relation of the operators and the truncation rules of the correlators. The outputs of SymGF are the desired NEGF that appear in the transport formula, in terms of the unperturbed Green's function of the device scattering region and its coupling to the device electrodes. For complicated transport analysis involving strong interactions and correlations, SymGF provides significant assistance in analytical derivations. Using this tool, we investigate coherent quantum transport in a double quantum dot system where strong on-site interaction exists in the side-coupled quantum dot. Results obtained by the higher-order approximation and Hartree-Fock approximation are compared. The higher-order approximation reveals Kondo resonance features in the density of states and conductances. Results are compared both qualitatively and quantitatively to the experimental data reported in the literature.
Bandyopadhyay, S
1999-01-01
Intriguing dichotomies in quantum measurement theory involving the role of the obersever, objective reality, collapse of wavefunctions and actualization of a measurement outcome are cast into a patholigical gedanken experiment involving a single electron in a double quantum dot system coupled via a weak link.
High-frequency manipulation of few-electron double quantum dots-toward spin qubits
Kodera, T.; van der Wiel, W. G.; Ono, K.; Sasaki, S.; Fujisawa, T.; Tarucha, S.
2004-04-01
We use a photon-assisted tunneling (PAT) technique to study the high-frequency response of one- and two-electron states in a semiconductor vertically coupled double-dot system. In particular, PAT associated with two-electron spin states in the spin-blockade regime is observed up to the absorption of 10 photons, indicating the preservation of long relaxation times and hence the robustness of our electron spin device under strong microwave irradiation. An alternative double-dot structure with greater flexibility in tuning the inter-dot coupling is presented and its transport characteristics are discussed. This structure is proposed for high-frequency control of two-electron spin states, as required for quantum computation schemes using electron spins in quantum dots.
Charge sensed Pauli blockade in a metal-oxide-semiconductor lateral double quantum dot.
Nguyen, Khoi T; Lilly, Michael P; Nielsen, Erik; Bishop, Nathan; Rahman, Rajib; Young, Ralph; Wendt, Joel; Dominguez, Jason; Pluym, Tammy; Stevens, Jeffery; Lu, Tzu-Ming; Muller, Richard; Carroll, Malcolm S
2013-01-01
We report Pauli blockade in a multielectron silicon metal-oxide-semiconductor double quantum dot with an integrated charge sensor. The current is rectified up to a blockade energy of 0.18 ± 0.03 meV. The blockade energy is analogous to singlet-triplet splitting in a two electron double quantum dot. Built-in imbalances of tunnel rates in the MOS DQD obfuscate some edges of the bias triangles. A method to extract the bias triangles is described, and a numeric rate-equation simulation is used to understand the effect of tunneling imbalances and finite temperature on charge stability (honeycomb) diagram, in particular the identification of missing and shifting edges. A bound on relaxation time of the triplet-like state is also obtained from this measurement.
Gutierrez, Rafael M.; Castañeda, Arcesio
2009-08-01
Quantum mechanics explains the existence and properties of the chemical bond responsible for the formation of molecules from isolated atoms. In this work we study quantum states of Double Quantum Wells, DQW, formed from isolated Single Quantum Wells, SQWs, that can be considered metamaterials. Using the quantum chemistry definition of the covalent bond, we discuss molecular states in DQW as a kind of nanochemistry of metamaterials with new properties, in particular new optical properties. An important particularity of such nanochemistry, is the possible experimental control of the geometrical parameters and effective masses characterizing the semiconductor heterostructures represented by the corresponding DQW. This implies a great potential for new applications of the controlled optical properties of the metamaterials. The use of ab initio methods of intensive numerical calculations permits to obtain macroscopic optical properties of the metamaterials from the fundamental components: the spatial distribution of the atoms and molecules constituting the semiconductor layers. The metamaterial new optical properties emerge from the coexistence of many body processes at atomic and molecular level and complex quantum phenomena such as covalent-like bonds at nanometric dimensions.
Soudani, S.; Jeanneau, E.; Jelsch, C.; Lefebvre, F.; Ben Nasr, C.
2017-10-01
The synthesis and the X-ray structure of the Zn(II) zwitterionic complex:1-ethylpiperaziniumtrichlorozincate (II) are described. In the atomic arrangement, the ZnCl3N entities, grouped in pairs, are deployed along the b-axis to form layers. The organic entities are inserted between these layers through Nsbnd H⋯Cl and Csbnd H⋯Cl hydrogen bonds to form infinite three-dimensional network. The 3D Hirshfeld surfaces were investigated for intermolecular interactions. The optimized geometry, Mulliken charge distribution, molecular electrostatic potential (MEP) maps and thermodynamic properties have been calculated using the Lee-Yang-Parr correlation functional B3LYP with the LanL2DZ basis set. The HOMO and LUMO energy gap and chemical reactivity parameters were made. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray crystal structure. The vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed the attribution of the NMR peaks and of the IR bands.
Energy Technology Data Exchange (ETDEWEB)
Pashynska, Vlada, E-mail: vlada@vl.kharkov.ua [B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Lenin Ave., 47, 61103 Kharkov (Ukraine); Stepanian, Stepan [B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Lenin Ave., 47, 61103 Kharkov (Ukraine); Gömöry, Agnes; Vekey, Karoly [Institute of Organic Chemistry of Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Magyar tudosok korutja, 2, Budapest H-1117 (Hungary); Adamowicz, Ludwik [University of Arizona, Department of Chemistry and Biochemistry, Tucson, AZ 85721 (United States)
2015-07-09
Highlights: • Competitive binding of artemisinin agents and aspirin with phospholipids is shown. • Complexation between the antimalarial drugs and aspirin molecules is also found. • Energetically favorable structures of the model complexes are identified by DFT. • Membranotropic activity of the studied drugs can be modified under joint usage. - Abstract: Study of intermolecular interactions of antimalarial artemisinin-type drugs and aspirin with membrane phospholipids is important in term of elucidation of the drugs activity modification under their joint usage. Combined experimental and computational study of the interaction of dihydroartemisinin, α-artemether, and artesunate with aspirin (ASP) and dipalmitoylphosphatidylcholine (DPPC) is performed by electrospray ionization (ESI) mass spectrometry and by DFT B3LYP/aug-cc-pVDZ methods. The results of the ESI investigation of systems containing artemisinin-type agent, ASP and DPPC, reveal a competition between the antimalarial agents and ASP for binding with DPPC molecules. The complexation between the antimalarial drugs and ASP is also found. Observed phenomena suggest that membranotropic activity of artemisin-type agents and aspirin is modified under their combined usage. To elucidate structure-energy characteristics of the non-covalent complexes studied the model DFT calculations are performed for dihydroartemisinin · ASP complex and complexes of the each drug with phosphatidylcholine head of DPPC in neutral and cationized forms.
Charge sensing of a few-donor double quantum dot in silicon
Energy Technology Data Exchange (ETDEWEB)
Watson, T. F., E-mail: tfwatson15@gmail.com; Weber, B.; Büch, H.; Fuechsle, M.; Simmons, M. Y., E-mail: michelle.simmons@unsw.edu.au [Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, University of New South Wales, Sydney, New South Wales 2052 (Australia)
2015-12-07
We demonstrate the charge sensing of a few-donor double quantum dot precision placed with atomic resolution scanning tunnelling microscope lithography. We show that a tunnel-coupled single electron transistor (SET) can be used to detect electron transitions on both dots as well as inter-dot transitions. We demonstrate that we can control the tunnel times of the second dot to the SET island by ∼4 orders of magnitude by detuning its energy with respect to the first dot.
Spin-Flip Process through Double Quantum Dots Coupled to Ferromagnetic Leads
Institute of Scientific and Technical Information of China (English)
YAN Cong-Hua; WU Shao-Quan; HUANG Rui; SUN Wei-Li
2006-01-01
@@ We investigate the spin-flip process through double quantum dots coupled to two ferromagnetic leads in series.By means of the slave-boson mean-field approximation, we calculate the density of states in the Kondo regime for two different configurations of the leads. It is found that transport shows some remarkable properties depending on the spin-flip strength. These effects may be useful in exploiting the role of electronic correlation in spintronics.
Closed form solution for a double quantum well using Groebner basis
Energy Technology Data Exchange (ETDEWEB)
Acus, A [Institute of Theoretical Physics and Astronomy, Vilnius University, A Gostauto 12, LT-01108 Vilnius (Lithuania); Dargys, A, E-mail: dargys@pfi.lt [Center for Physical Sciences and Technology, Semiconductor Physics Institute, A Gostauto 11, LT-01108 Vilnius (Lithuania)
2011-07-01
Analytical expressions for the spectrum, eigenfunctions and dipole matrix elements of a square double quantum well (DQW) are presented for a general case when the potential in different regions of the DQW has different heights and the effective masses are different. This was achieved by using a Groebner basis algorithm that allowed us to disentangle the resulting coupled polynomials without explicitly solving the transcendental eigenvalue equation.
Double-Sided Junctions Enable High-Performance Colloidal-Quantum-Dot Photovoltaics.
Liu, Mengxia; de Arquer, F Pelayo García; Li, Yiying; Lan, Xinzheng; Kim, Gi-Hwan; Voznyy, Oleksandr; Jagadamma, Lethy Krishnan; Abbas, Abdullah Saud; Hoogland, Sjoerd; Lu, Zhenghong; Kim, Jin Young; Amassian, Aram; Sargent, Edward H
2016-06-01
The latest advances in colloidal-quantum-dot material processing are combined with a double-sided junction architecture, which is done by efficiently incorporating indium ions in the ZnO eletrode. This platform allows the collection of all photogenerated carriers even at the maximum power point. The increased depletion width in the device facilitates full carrier collection, leading to a record 10.8% power conversion efficiency.
Phonon-assisted gain in a semiconductor double quantum dot maser.
Gullans, M J; Liu, Y-Y; Stehlik, J; Petta, J R; Taylor, J M
2015-05-15
We develop a microscopic model for the recently demonstrated double-quantum-dot maser. In characterizing the gain of this device we find that, in addition to the direct stimulated emission of photons, there is a large contribution from the simultaneous emission of a photon and a phonon, i.e., the phonon sideband. We show that this phonon-assisted gain typically dominates the overall gain, which leads to masing. Recent experimental data are well fit with our model.
Interplay between electron spin and orbital pseudospin in double quantum dots
Park, Sooa; Yang, S. -R. Eric
2005-01-01
We investigate theoretically spin and orbital pseudospin magnetic properties of a molecular orbital in parabolic and elliptic double quantum dots (DQDs). In our many body calculation we include intra- and inter-dot electron-electron interactions, in addition to the intradot exchange interaction of `p' orbitals. We find for parabolic DQDs that, except for the half or completely filled molecular orbital, spins in different dots are ferromagnetically coupled while orbital pseudospins are antifer...
Correlation Effects on the Coupled Plasmon Modes of a Double Quantum Well
DEFF Research Database (Denmark)
Hill, N. P. R.; Nicholls, J. T.; Linfield, E. H.;
1997-01-01
At temperatures comparable to the Fermi temperature, we have measured a plasmon enhanced Coulomb drag in a GaAs/AlGaAs double quantum well electron system. This measurement provides a probe of the many-body corrections to the coupled plasmon modes, and we present a detailed comparison between...... experiment and theory testing the validity of local field theories. Using a perpendicular magnetic field to raise the magnetoplasmon energy we can induce a crossover to single-particle Coulomb scattering....
C*-Structure of Quantum Double for Finite Hopf C*-Algebra
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
Let H be a finite Hopf C*-algebra and H' be its dual Hopf algebra. Drinfeld's quantum double D(H) of H is a Hopf *-algebra. There is a faithful positive linear functional θ on D(H). Through the associated Gelfand-Naimark-Segal (GNS) representation, D(H) has a faithful *-representation so that it becomes a Hopf C*-algebra. The canonical embedding map of H into D(H) is isometric.
Electron spin resonance and spin-valley physics in a silicon double quantum dot.
Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen
2014-05-14
Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.
Double-Paddle Oscillators as Probes of Quantum Turbulence in the Zero Temperature Limit
Schmoranzer, David; Jackson, Martin; Zemma, Elisa; Luzuriaga, Javier
2016-11-01
We present a technical report on our tests of a double-paddle oscillator as a detector of quantum turbulence in superfluid 4 He at low temperatures ranging from 20 to 1100 mK. The device, known to operate well in the two-fluid regime (Zemma and Luzuriaga in J Low Temp Phys 166:171-181, 2012), is also capable of detecting quantum turbulence in the zero temperature limit. The oscillator demonstrated Lorentzian responses with quality factors of order 10^5 in vacuum, and displayed negative-Duffing resonances in liquid, even at moderate drives. In superfluid He-II at low temperatures, its sensitivity was adversely affected by acoustic damping at higher harmonics. While it successfully created and detected the quantum turbulence, its overall performance does not compare favourably with other oscillators such as tuning forks.
Spin-orbit effects in carbon-nanotube double quantum dots
DEFF Research Database (Denmark)
Weiss, S; Rashba, E I; Kuemmeth, Ferdinand;
2010-01-01
We study the energy spectrum of symmetric double quantum dots in narrow-gap carbon nanotubes with one and two electrostatically confined electrons in the presence of spin-orbit and Coulomb interactions. Compared to GaAs quantum dots, the spectrum exhibits a much richer structure because of the spin...... between the dots. For the two-electron regime, the detailed structure of the spin-orbit split energy spectrum is investigated as a function of detuning between the quantum dots in a 22-dimensional Hilbert space within the framework of a single-longitudinal-mode model. We find a competing effect......-orbit interaction that couples the electron's isospin to its real spin through two independent coupling constants. In a single dot, both constants combine to split the spectrum into two Kramers doublets while the antisymmetric constant solely controls the difference in the tunneling rates of the Kramers doublets...
Energy Technology Data Exchange (ETDEWEB)
An, Xing-Tao, E-mail: anxt2005@163.com [School of Sciences, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018 (China); Mu, Hui-Ying [Department of Chemistry and Environmental Engineering, Hebei Chemical and Pharmaceutical Vocational Technology College, Shijiazhuang, Hebei 050026 (China); Li, Yu-Xian [College of Physical Science and Information Engineering, Hebei Normal University, and Hebei Advanced Thin Films Laboratory, Shijiazhuang, Hebei 050016 (China); Liu, Jian-Jun [College of Physical Science and Information Engineering, Hebei Normal University, and Hebei Advanced Thin Films Laboratory, Shijiazhuang, Hebei 050016 (China); Physics Department, Shijiazhuang University, Shijiazhuang 050035 (China)
2011-10-31
A four-terminal parallel double quantum dots (QDs) device is proposed to generate and detect the spin polarization in QDs. It is found that the spin accumulation in QDs and the spin-polarized currents in the upper and down leads can be generated when a bias voltage is applied between the left and right leads. It is more interesting that the spin polarization in the QDs can be detected using the upper and down leads. Moreover, the direction and magnitude of the spin polarization in the QDs, and in the upper and down leads can be tuned by the energy levels of QDs and the bias. -- Highlights: → The spin polarization in the quantum dots can be generated and controlled. → The spin polarization in quantum dots can be detected by the nonferromagnetic leads. → The system our studied is a discrete level spin Hall system.
Asymmetric double quantum well structure as a tunable detector in the far-infrared range
Shin, U; Park, M J; Lee, S J
1999-01-01
The eigenvalues and the wave functions of GaAs/Al sub x Ga sub 1 sub - sub x As asymmetric double quantum well structure have been calculated by using of complex energy method. Based on theoretical calculations, tuning ranges from 9 to 14 mu m are predicted for the proposed asymmetric coupled-quantum-well structure. In addition we calculated the energy eigenvalues and the wave functions of an electron in GaAs/Al sub x Ga sub 1 sub - sub x As single quantum well structure (including delta-perturbation). the variation in E sub 1 , the ground state energy eigenvalue of the electron, depends on the strength and position of the perturbation within the well.
Quantum-coupled radial-breathing oscillations in double-walled carbon nanotubes.
Liu, Kaihui; Hong, Xiaoping; Wu, Muhong; Xiao, Fajun; Wang, Wenlong; Bai, Xuedong; Ager, Joel W; Aloni, Shaul; Zettl, Alex; Wang, Enge; Wang, Feng
2013-01-01
Van der Waals-coupled materials, ranging from multilayers of graphene and MoS(2) to superlattices of nanoparticles, exhibit rich emerging behaviour owing to quantum coupling between individual nanoscale constituents. Double-walled carbon nanotubes provide a model system for studying such quantum coupling mediated by van der Waals interactions, because each constituent single-walled nanotube can have distinctly different physical structures and electronic properties. Here we systematically investigate quantum-coupled radial-breathing mode oscillations in chirality-defined double-walled nanotubes by combining simultaneous structural, electronic and vibrational characterizations on the same individual nanotubes. We show that these radial-breathing oscillations are collective modes characterized by concerted inner- and outer-wall motions, and determine quantitatively the tube-dependent van der Waals potential governing their vibration frequencies. We also observe strong quantum interference between Raman scattering from the inner- and outer-wall excitation pathways, the relative phase of which reveals chirality-dependent excited-state potential energy surface displacement in different nanotubes.
Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane
Knapp, T. J.; Mohr, R. T.; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H.; Wu, Xian; Ward, Daniel R.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.
2016-04-01
We report the fabrication and characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. In the past, all gate-defined quantum dots in Si/SiGe heterostructures were formed on top of strain-graded virtual substrates. The strain grading process necessarily introduces misfit dislocations into a heterostructure, and these defects introduce lateral strain inhomogeneities, mosaic tilt, and threading dislocations. The use of a SiGe nanomembrane as the virtual substrate enables the strain relaxation to be entirely elastic, eliminating the need for misfit dislocations. However, in this approach the formation of the heterostructure is more complicated, involving two separate epitaxial growth procedures separated by a wet-transfer process that results in a buried non-epitaxial interface 625 nm from the quantum dot. We demonstrate that in spite of this buried interface in close proximity to the device, a double quantum dot can be formed that is controllable enough to enable tuning of the inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of an applied magnetic field.
Andreev and Majorana bound states in single and double quantum dot structures
Silva, Joelson F.; Vernek, E.
2016-11-01
We present a numerical study of the emergence of Majorana and Andreev bound states in a system composed of two quantum dots, one of which is coupled to a conventional superconductor, SC1, and the other connects to a topological superconductor, SC2. By controlling the interdot coupling we can drive the system from two single (uncoupled) quantum dots to double (coupled) dot system configurations. We employ a recursive Green’s function technique that provides us with numerically exact results for the local density of states of the system. We first show that in the uncoupled dot configuration (single dot behavior) the Majorana and the Andreev bound states appear in an individual dot in two completely distinct regimes. Therefore, they cannot coexist in the single quantum dot system. We then study the coexistence of these states in the coupled double dot configuration. In this situation we show that in the trivial phase of SC2, the Andreev states are bound to an individual quantum dot in the atomic regime (weak interdot coupling) or extended over the entire molecule in the molecular regime (strong interdot coupling). More interesting features are actually seen in the topological phase of SC2. In this case, in the atomic limit, the Andreev states appear bound to one of the quantum dots while a Majorana zero mode appears in the other one. In the molecular regime, on the other hand, the Andreev bound states take over the entire molecule while the Majorana state remains always bound to one of the quantum dots.
Gharbi, A.; Touloum, S.; Bouda, A.
2015-04-01
We study the Klein-Gordon equation with noncentral and separable potential under the condition of equal scalar and vector potentials and we obtain the corresponding relativistic quantum Hamilton-Jacobi equation. The application of the quantum Hamilton-Jacobi formalism to the double ring-shaped Kratzer potential leads to its relativistic energy spectrum as well as the corresponding eigenfunctions.
Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane
Knapp, T. J.; Mohr, R. T.; Li, Yize Stephanie; Thorgrimsson, Brandur; Foote, Ryan H.; Wu, Xian; Ward, Daniel R.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.
We report the characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. Previously, all heterostructures used to form quantum dots were created using the strain-grading method of strain relaxation, a method that necessarily introduces misfit dislocations into a heterostructure and thereby degrades the reproducibility of quantum devices. Using a SiGe nanomembrane as a virtual substrate eliminates the need for misfit dislocations but requires a wet-transfer process that results in a non-epitaxial interface in close proximity to the quantum dots. We show that this interface does not prevent the formation of quantum dots, and is compatible with a tunable inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of the applied magnetic field. This work was supported in part by ARO (W911NF-12-0607), NSF (DMR-1206915, PHY-1104660), and the United States Department of Defense. The views and conclusions contained in this document are those of the author and should not be interpreted as representing the official policies, either expressly or implied, of the US Government. T.J. Knapp et al. (2015). arXiv:1510.08888 [cond-mat.mes-hall].
Entanglement of mixed quantum states for qubits and qudit in double photoionization of atoms
Energy Technology Data Exchange (ETDEWEB)
Chakraborty, M., E-mail: bminakshi@yahoo.com [Department of Physics, Asansol Girls’ College, Asansol 713304 (India); Sen, S. [Department of Physics, Triveni Devi Bhalotia College, Raniganj 713347 (India)
2015-08-15
Highlights: • We study tripartite entanglement between two electronic qubits and an ionic qudit. • We study bipartite entanglement between any two subsystems of a tripartite system. • We have presented a quantitative application of entangled properties in Neon atom. - Abstract: Quantum entanglement and its paradoxical properties are genuine physical resources for various quantum information tasks like quantum teleportation, quantum cryptography, and quantum computer technology. The physical characteristic of the entanglement of quantum-mechanical states, both for pure and mixed, has been recognized as a central resource in various aspects of quantum information processing. In this article, we study the bipartite entanglement of one electronic qubit along with the ionic qudit and also entanglement between two electronic qubits. The tripartite entanglement properties also have been investigated between two electronic qubits and an ionic qudit. All these studies have been done for the single-step double photoionization from an atom following the absorption of a single photon without observing spin orbit interaction. The dimension of the Hilbert space of the qudit depends upon the electronic state of the residual photoion A{sup 2+}. In absence of SOI, when Russell–Saunders coupling (L–S coupling) is applicable, dimension of the qudit is equal to the spin multiplicity of A{sup 2+}. For estimations of entanglement and mixedness, we consider the Peres–Horodecki condition, concurrence, entanglement of formation, negativity, linear and von Neumann entropies. In case of L–S coupling, all the properties of a qubit–qudit system can be predicted merely with the knowledge of the spins of the target atom and the residual photoion.
Arivazhagan, G; Shanmugam, R; Elangovan, A
2013-03-15
The results of FTIR spectral measurement on equimolar diisopropyl ether-butyric acid binary mixture and quantum chemical calculations on the complex molecule have been presented. Dielectric studies have been carried out on the binary mixture over the entire composition range and at four different temperatures 303 K, 308 K, 313 K and 318 K. n-Butyric acid seems to prefer less polar ether to interact with it. It appears that the usual interpretation of variation of static dielectric constant and positive deviation of excess permittivity from ideal mixture behavior needs to be relooked.
Kurian, P; Dunston, G; Lindesay, J
2016-02-21
Macroscopic quantum effects in living systems have been studied widely in pursuit of fundamental explanations for biological energy transport and sensing. While it is known that type II endonucleases, the largest class of restriction enzymes, induce DNA double-strand breaks by attacking phosphodiester bonds, the mechanism by which simultaneous cutting is coordinated between the catalytic centers remains unclear. We propose a quantum mechanical model for collective electronic behavior in the DNA helix, where dipole-dipole oscillations are quantized through boundary conditions imposed by the enzyme. Zero-point modes of coherent oscillations would provide the energy required for double-strand breakage. Such quanta may be preserved in the presence of thermal noise by the enzyme's displacement of water surrounding the DNA recognition sequence. The enzyme thus serves as a decoherence shield. Palindromic mirror symmetry of the enzyme-DNA complex should conserve parity, because symmetric bond-breaking ceases when the symmetry of the complex is violated or when physiological parameters are perturbed from optima. Persistent correlations in DNA across longer spatial separations-a possible signature of quantum entanglement-may be explained by such a mechanism.
Optical absorption in asymmetric double quantum wells driven by two intense terahertz fields
Institute of Scientific and Technical Information of China (English)
Wu Hong-Wei; Mi Xian-Wu
2013-01-01
Optical absorption is investigated for asymmetric double quantum wells driven by a resonant terahertz field and a varied terahertz field,both polarized along the growth direction.Rich nonlinear dynamics of the replica peak and the Autler-Townes splitting of various dressed states are systematically studied in undoped asymmetric double quantum wells by taking account of multiple factors,such as the frequency of the varied terahertz field and the strength of the resonant terahertz field.Each electron subband splits into two dressed states when the resonant terahertz field is applied in the absence of the varied terahertz field,the optical absorption spectrum shows the first-order Autler-Townes splitting of the electron subbands.When a varied terahertz field is added into the resonant system,the replica peak and the second-order Autler-Townes splitting of the dressed states near the band edge respectively emerge when the varied terahertz field is non-resonant and resonant with these dressed states.Wben the strength of the resonant terahertz field is increased,the first-order Autler-Townes double peaks and the replica peak in the optical absorption spectrum shift with the shifts of the dressed states.The presented results have potential applications in electro-optical devices.
Intermolecular Contrast in Atomic Force Microscopy Images without Intermolecular Bonds
Hämäläinen, Sampsa K.; van der Heijden, N.J. (Nadine); van der Lit, Joost; den Hartog, Stephan; Liljeroth, Peter; Swart, Ingmar
2014-01-01
Intermolecular features in atomic force microscopy images of organic molecules have been ascribed to intermolecular bonds. A recent theoretical study [P. Hapala et al., Phys. Rev. B 90, 085421 (2014)] showed that these features can also be explained by the flexibility of molecule-terminated tips. We
Solitary and double-layer structures in quantum bi-ion plasma
Shahmansouri, Mehran; Tribeche, Mouloud
2016-06-01
Weak ion-acoustic solitary waves (IASWs) in an unmagnetized quantum plasmas having two-fluid ions and fluid electrons are considered. Using the one-dimensional quantum hydrodynamics model and then the reductive perturbation technique, a generalized form of nonlinear quantum Korteweg-de Vries (KdV) equation governing the dynamics of weak ion acoustic solitary waves is derived. The effects of ion population, warm ion temperature, quantum diffraction, and polarity of ions on the nonlinear properties of these IASWs are analyzed. It is found that our present plasma model may support compressive as well as rarefactive solitary structures. Furthermore, formation and characteristics properties of IA double layers in the present bi-ion plasma model are investigated. The results of this work should be useful and applicable in understanding the wide relevance of nonlinear features of localized electro-acoustic structures in laboratory and space plasma, such as in super-dense astrophysical objects [24] and in the Earth's magnetotail region (Parks [43]. The implications of our results in some space plasma situations are discussed.
Intrinsic errors in transporting a single-spin qubit through a double quantum dot
Li, Xiao; Barnes, Edwin; Kestner, J. P.; Das Sarma, S.
2017-07-01
Coherent spatial transport or shuttling of a single electron spin through semiconductor nanostructures is an important ingredient in many spintronic and quantum computing applications. In this work we analyze the possible errors in solid-state quantum computation due to leakage in transporting a single-spin qubit through a semiconductor double quantum dot. In particular, we consider three possible sources of leakage errors associated with such transport: finite ramping times, spin-dependent tunneling rates between quantum dots induced by finite spin-orbit couplings, and the presence of multiple valley states. In each case we present quantitative estimates of the leakage errors, and discuss how they can be minimized. The emphasis of this work is on how to deal with the errors intrinsic to the ideal semiconductor structure, such as leakage due to spin-orbit couplings, rather than on errors due to defects or noise sources. In particular, we show that in order to minimize leakage errors induced by spin-dependent tunnelings, it is necessary to apply pulses to perform certain carefully designed spin rotations. We further develop a formalism that allows one to systematically derive constraints on the pulse shapes and present a few examples to highlight the advantage of such an approach.
Electronic structures of GaAs/AlxGa1-xAs quantum double rings
Directory of Open Access Journals (Sweden)
Li Shu-Shen
2006-01-01
Full Text Available AbstractIn the framework of effective mass envelope function theory, the electronic structures of GaAs/AlxGa1-xAs quantum double rings (QDRs are studied. Our model can be used to calculate the electronic structures of quantum wells, wires, dots, and the single ring. In calculations, the effects due to the different effective masses of electrons and holes in GaAs and AlxGa1-xAs and the valence band mixing are considered. The energy levels of electrons and holes are calculated for different shapes of QDRs. The calculated results are useful in designing and fabricating the interrelated photoelectric devices. The single electron states presented here are useful for the study of the electron correlations and the effects of magnetic fields in QDRs.
Photoluminescence study of InGaN/GaN double quantum wells with varying barrier widths
Ryu, M Y; Shin, E J; Lee, J I; Yu, S K; Oh, E S; Park, Y J; Park, H S; Kim, T I
2000-01-01
We report the results of photoluminescence (PL) and time-resolved PL studies on InGaN/GaN double quantum well (DQW) samples with different barrier widths. The barrier-width dependence of the PL emission energy and intensity are discussed. The PL as a function of excitation density can be well explained in terms of the quantum-confined Stark effect (QCSE). The temporal behavior of the PL was also studied. As the barrier width increases, the decay times tau sub 1 and tau sub 2 , decrease from 1.02 ns and 6.99 ns to 0.32 ns and 1.09 ns, respectively. The PL efficiency and the decay lifetime depend on the barrier width.
Electron-nuclear interaction in 13C nanotube double quantum dots
DEFF Research Database (Denmark)
Churchill, H O H; Bestwick, A J; Harlow, J W
2009-01-01
environment on the evolution of confined electron spins, we have fabricated and measured gate-defined double quantum dots with integrated charge sensors made from single-walled carbon nanotubes with a variable concentration of 13C (nuclear spin I=1/2) among the majority zero-nuclear-spin 12C atoms. We observe...... strong isotope effects in spin-blockaded transport, and from the magnetic field dependence estimate the hyperfine coupling in 13C nanotubes to be of the order of 100 ¿µeV, two orders of magnitude larger than anticipated. 13C-enhanced nanotubes are an interesting system for spin-based quantum information...
Cho, Seungho; Jung, Sungwook; Jeong, Sanghwa; Bang, Jiwon; Park, Joonhyuck; Park, Youngrong; Kim, Sungjee
2013-01-08
Layered double hydroxide-quantum dot (LDH-QD) composites are synthesized via a room temperature LDH formation reaction in the presence of QDs. InP/ZnS (core/shell) QD, a heavy metal free QD, is used as a model constituent. Interactions between QDs (with negative zeta potentials), decorated with dihydrolipoic acids, and inherently positively charged metal hydroxide layers of LDH during the LDH formations are induced to form the LDH-QD composites. The formation of the LDH-QD composites affords significantly enhanced photoluminescence quantum yields and thermal- and photostabilities compared to their QD counterparts. In addition, the fluorescence from the solid LDH-QD composite preserved the initial optical properties of the QD colloid solution without noticeable deteriorations such as red-shift or deep trap emission. Based on their advantageous optical properties, we also demonstrate the pseudo white light emitting diode, down-converted by the LDH-QD composites.
Optimal control of a charge qubit in a double quantum dot with a Coulomb impurity
Coden, Diego S. Acosta; Romero, Rodolfo H.; Ferrón, Alejandro; Gomez, Sergio S.
2017-02-01
We study the efficiency of modulated external electric pulses to produce efficient and fast charge localization transitions in a two-electron double quantum dot. We use a configuration interaction method to calculate the electronic structure of a quantum dot model within the effective mass approximation. The interaction with the electric field is considered within the dipole approximation and optimal control theory is applied to design high-fidelity ultrafast pulses in pristine samples. We assessed the influence of the presence of Coulomb charged impurities on the efficiency and speed of the pulses. A protocol based on a two-step optimization is proposed for preserving both advantages of the original pulse. The processes affecting the charge localization is explained from the dipole transitions of the lowest lying two-electron states, as described by a discrete model with an effective electron-electron interaction.
Electronic structure of GaAs/AlGaAs quantum double rings in lateral electric field
Institute of Scientific and Technical Information of China (English)
Y.Yao; T.Ochiai; T.Mano; T.Kuroda; T.Noda; N.Koguchi; K.Sakoda
2009-01-01
A three-dimensional model of GaAs/A1GaAs quantum double rings in the lateral static electric field is investigated theoretically.The eigenvalue problem with the effective-mass approximation is solved by means of the finite-element method.The energy levels and wave functions of quantum-confined electrons and heavy holes are obtained and show an agreement with our previous theoretical and experimental studies.It is shown in the approximation of neglecting the Coulomb attraction between the electron and heavy hole that a relatively large Stark shift of exciton emission of 4 meV is attainable with an applied electric field of 0.7 kV/cm.
Dynamical entanglement formation and dissipation effects in two double quantum dots
Energy Technology Data Exchange (ETDEWEB)
Contreras-Pulido, L D [Centro de Investigacion CientIfica y de Educacion Superior de Ensenada, Apartado Postal 2732, Ensenada, BC 22860 (Mexico); Rojas, F [Departamento de Fisica Teorica, Centro de Ciencias de la Materia Condensada, Universidad Nacional Autonoma de Mexico, Ensenada, Baja California 22800 (Mexico)
2006-11-01
We study the static and dynamic formation of entanglement in charge states of a two double quantum dot array with two mobile electrons under the effect of an external driving field. We include dissipation via contact with a phonon bath. By using the density matrix formalism and an open quantum system approach, we describe the dynamical behaviour of the charge distribution (polarization), concurrence (measure of the degree of entanglement) and Bell state probabilities (two qubit states with maximum entanglement) of such a system, including the role of dot asymmetry and temperature effects. Our results show that it is possible to obtain entangled states as well as a most probable Bell state, which can be controlled by the driving field. We also evaluate how the entanglement formation based on charge states deteriorates as the temperature or asymmetry increases.
Collective Behavior of Interwell Excitons in GaAs/AlGaAs Double Quantum Wells
DEFF Research Database (Denmark)
Larionov, A. V.; Timofeev, V. B.; Hvam, Jørn Märcher
2000-01-01
Photoluminescence spectra of interwell excitons in double GaAs/AlGaAs quantum wells (n-i-n structures) have been investigated (an interwell excition in these systems is an electron-hole pair spatially separated by a narrow AlAs barrier). Under resonance excitation by circular polarized light......, the luminescence line of interwell excitions exhibits a significant narrowing and a drastic increase in the degree of circular polarization of photoluminescence with increasing exciton concentration. It is found that the radiative recombination rate significantly increases under these conditions. This phenomenon...
The electronic properties of concentric double quantum ring and possibility designing XOR gate
AL-Badry, Lafy. F.
2017-03-01
In this paper I have investigated the Aharonov-Bohm oscillation in concentric double quantum ring. The outer ring attached to leads while the inner ring only tunnel-coupled to the outer ring. The effect of inner ring on electron transport properties through outer ring studied and found that the conductance spectrum consists of two types of oscillations. One is the normal Aharonov-Bohm oscillation, and other is a small oscillations superposed above AB oscillation. The AB oscillation utilized to designing nanoscale XOR gate by choosing the magnetic flux and tuning the gate voltages which realization XOR gate action.
A Remark on CFT Realization of Quantum Doubles of Subfactors: Case Index { < 4}
Bischoff, Marcel
2016-03-01
It is well known that the quantum double {D(Nsubset M)} of a finite depth subfactor {Nsubset M}, or equivalently the Drinfeld center of the even part fusion category, is a unitary modular tensor category. It is big open conjecture that all (unitary) modular tensor categories arise from conformal field theory. We show that for every subfactor {Nsubset M} with index {[M:N] construct completely rational nets with the opposite braiding of {{SU(2)}_k} and use the well-known fact that all subfactors with index {[M:N] < 4} arise by {α}-induction from {{SU(2)}_k}.
Hole subband structure in single and double p-type {delta}-doped diamond quantum wells
Energy Technology Data Exchange (ETDEWEB)
Rodriguez-Vargas, I. [Facultad de Ciencias, Univ. Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca (Mexico); Duque, C.A. [Inst. de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Univ. Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca (Mexico); Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain); Velasco, V.R. [Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)
2007-07-01
Heavy, light, and split-off hole states in single and double p-{delta}-doped diamond quantum wells are studied with the use of a 6 x 6 k.p model. The effective mass Hamiltonian is solved using a local density Thomas-Fermi-Dirac approximation for the description of the band bending profile. The features of the valence band spectrum are briefly discussed in both cases. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads
Institute of Scientific and Technical Information of China (English)
Yan Cong-Hua; Wu Shao-Quan; Huang Rui; Sun Wei-Li
2008-01-01
We investigate the spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads in series.By means of the slave-boson mean-field approximation,we calculate the density of states in the Kondo regime for two different configurations of the leads.It is found that the transport shows some remarkable properties depending on the spin-flip strength.These effects may be useful in exploiting the role of electronic correlation in spintronics.
Temperature-dependent exciton recombination in asymmetrical ZnCdSe/ZnSe double quantum wells
Yu Guang You; Zhang, J Y; Zheng, Z H; Yang, B J; Zhao Xiao Wei; Shen De Zhen; Kong Xiang Gui
1999-01-01
Temperature-dependent exciton recombination in asymmetrical ZnCdSe/ZnSe double quantum wells is studied by recording photoluminescence spectra and photoluminescence decay spectra. The exciton tunnelling from the wide well to the narrow well and the thermal dissociation of excitons are two factors that influence the exciton recombination in this structure. In the narrow well, both of the two processes decrease the emission intensity, whereas, in the wide well, these two processes have contrary influences on the exciton density. The change of the emission intensity depends on which is the stronger one. (author)
Niculescu, E. C.
2017-02-01
Electromagnetically induced transparency in an asymmetric double quantum well subjected to a non-resonant, intense laser field is theoretically investigated. We found that the energy levels configuration could be switched between a Λ-type and a ladder-type scheme by varying the non-resonant radiation intensity. This effect is due to the laser-induced electron tunneling between the wells and it allows a substantial flexibility in the manipulation of the optical properties. The dependence of the susceptibilities on the control field Rabi frequency, intensity of the nonresonant laser, and the control field detuning for both configurations are discussed and compared.
Relaxation and Dephasing in a Two-Electron 13C Nanotube Double Quantum Dot
DEFF Research Database (Denmark)
Churchill, H O H; Kuemmeth, Ferdinand; Harlow, J W
2009-01-01
We use charge sensing of Pauli blockade (including spin and isospin) in a two-electron 13C nanotube double quantum dot to measure relaxation and dephasing times. The relaxation time T1 first decreases with a parallel magnetic field and then goes through a minimum in a field of 1.4 T. We attribute...... both results to the spin-orbit-modified electronic spectrum of carbon nanotubes, which at high field enhances relaxation due to bending-mode phonons. The inhomogeneous dephasing time T2* is consistent with previous data on hyperfine coupling strength in 13C nanotubes....
Su, M Y; Sherwin, M S; Huntington, A S; Coldren, L A
2002-01-01
An undoped double quantum well (DQW) was driven with a terahertz (THz) electric field of frequency \\omega_{THz} polarized in the growth direction, while simultaneously illuminated with a near-infrared (NIR) laser at frequency \\omega_{NIR}. The intensity of NIR upconverted sidebands \\omega_{sideband}=\\omega_{NIR} + \\omega_{THz} was maximized when a dc voltage applied in the growth direction tuned the excitonic states into resonance with both the THz and NIR fields. There was no detectable upconversion far from resonance. The results demonstrate the possibility of using gated DQW devices for all-optical wavelength shifting between optical communication channels separated by up to a few THz.
Tunneling-Induced Transient Gain in an Asymmetric Double Quantum Well
Institute of Scientific and Technical Information of China (English)
XU Wei-Hua; WU Jin-Hui; GAO Jin-Yue
2004-01-01
@@ We investigate the transient behaviour of a weak probe in asymmetric double quantum well structures, where two excited states are coupled by resonant tunnelling through a thin barrier in a three-level system of electronic subbands. There is no external coherent coupling field applied, and we find that probe gain can be achieved during the transient process, which is induced by the coherent coupling of the upper states via the resonant tunnelling.We show that the transient behaviour of the probe depends on the coupling strength and the dephasing rate and can be tuned by changing the width of the tunnelling barrier.
Spin-Polarized Transport through Parallel Double Quantum Dots Coupled to Ferromagnetic Leads
Institute of Scientific and Technical Information of China (English)
HOU Tao; WU Shao-Quan; BI Ai-Hua; YANG Fu-Bin; SUN Wei-Li
2008-01-01
We theoretically study the spin-polarized transport phenomena of the parallel double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. The Hamiltonian is solved by means of the equation-of-motion approach. We analyse the transmission probability of this system in both the equilibrium and nonequilibrium cases, and our results reveal that the transport properties show some noticeable characteristics depending upon both the spin-polarized strength p and the value of the magnetic flux Ф. Moreover, in the parallel configuration, the position of the Kondo peak shifts while it remains unchanged for the antiparallel configuration. These effects might have some potential applications in spintronics.
An Electron-Nucleon Double Spin Solid-State Quantum Computer
Long, G L; Chen, H M; Long, Gui Lu; Ma, Ying-Jun; Chen, Hao-Ming
2003-01-01
An electron-nucleon double spin(ENDOS) solid-state quantum computer scheme is proposed. In this scheme, the qubits are the nuclear spins of phosphorus ion implanted on the (111) surface of $^{28}$Si substrate. An $^{13}$C atom on a scanning tunnelling probe tip is used both to complete single qubit and two-qubit control-not operation, and single qubit measurement. The scheme does not require interactions between qubits, and can accomplish two qubits without the use of SWAP gate. This scheme is scalable, and can be implemented with present-day or near-future technologies.
Coherent Coupling of Double Quantum Dots Embedded in a Mesoscopic Ring
Institute of Scientific and Technical Information of China (English)
吴绍全; 王顺金
2003-01-01
We theoretically study the properties of the ground state of a series-coupled double quantum dot embedded in a mesoscopic ring in the Kondo regime by means of the two-impurity Anderson Hamiltonian. The Hamiltonian is solved by means of the slave-boson mean-field theory. It is shown that two dots can be coupled coherently,which is reflected in the appearance of parity effects and the complex current-phase relation in this system. This system might be a possible candidate for future device applications.
Giant Persistent Current in a Mesoscopic Ring with Parallel-Coupled Double Quantum Dots
Institute of Scientific and Technical Information of China (English)
CHEN Xiong-Wen; WU Shao-Quan; WANG Peng; SUN Wei-Li
2004-01-01
@@ We theoretically study the properties of the ground state of the parallel-coupled double quantum dots embedded in a mesoscopic ring in the Kondo regime by means of the two-impurity Anderson Hamiltonian. The Hamiltonian is solved by means of the slave-boson mean-field theory. Our results show that in this system, the persistent current depends sensitively on both the parity of this system and the size of the ring. Two dots can be coupled coherently, which is reflected in the giant current peak in the strong coupling regime. This system might be a candidate for future device applications.
Energy Technology Data Exchange (ETDEWEB)
Chen, Yuan; Deng, Li [Department of Applied Physics, East China Jiaotong University, Nanchang, 330013 (China); Chen, Aixi, E-mail: aixichen@ecjtu.jx.cn [Department of Applied Physics, East China Jiaotong University, Nanchang, 330013 (China); Institute for Quantum Computing, University of Waterloo, Ontario N2L 3G1 (Canada)
2015-02-15
We investigate the nonlinear optical phenomena of the optical bistability and multistability via spontaneously generated coherence in an asymmetric double quantum well structure coupled by a weak probe field and a controlling field. It is shown that the threshold and hysteresis cycle of the optical bistability can be conveniently controlled only by adjusting the intensity of the SGC or the controlling field. Moreover, switching between optical bistability and multistability can be achieved. These studies may have practical significance for the preparation of optical bistable switching device.
InSb nanowire double quantum dots coupled to a superconducting microwave cavity
Wang, R.; Deacon, R. S.; Car, D.; Bakkers, E. P. A. M.; Ishibashi, K.
2016-05-01
By employing a micrometer precision mechanical transfer technique, we embed individual InSb nanowires into a superconducting coplanar waveguide resonator. We investigate the characteristics of a double quantum dot formed in an InSb nanowire interacting with a single mode microwave field. The charge stability diagram can be obtained from the amplitude and phase response of the resonator independently from the dc transport measurement. As the charge transits between dot-dot, or dot-lead, the change of resonator transmission is compared and the charge-cavity coupling strength is extracted to be in the magnitude of several MHz.
InSb nanowire double quantum dots coupled to a superconducting microwave cavity
Energy Technology Data Exchange (ETDEWEB)
Wang, R. [Advanced Device Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Deacon, R. S., E-mail: russell@riken.jp; Ishibashi, K. [Advanced Device Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan); Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); Car, D. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Bakkers, E. P. A. M. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Kavli Institute, Quantum Transport Group, Delft University of Technology, 2628 CJ Delft (Netherlands)
2016-05-16
By employing a micrometer precision mechanical transfer technique, we embed individual InSb nanowires into a superconducting coplanar waveguide resonator. We investigate the characteristics of a double quantum dot formed in an InSb nanowire interacting with a single mode microwave field. The charge stability diagram can be obtained from the amplitude and phase response of the resonator independently from the dc transport measurement. As the charge transits between dot-dot, or dot-lead, the change of resonator transmission is compared and the charge-cavity coupling strength is extracted to be in the magnitude of several MHz.
Desensitization of metastable intermolecular composites
Busse, James R [South Fork, CO; Dye, Robert C [Los Alamos, NM; Foley, Timothy J [Los Alamos, NM; Higa, Kelvin T [Ridgecrest, CA; Jorgensen, Betty S [Jemez Springs, NM; Sanders, Victor E [White Rock, NM; Son, Steven F [Los Alamos, NM
2011-04-26
A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.
Gresh, Nohad; Sponer, Judit E; Devereux, Mike; Gkionis, Konstantinos; de Courcy, Benoit; Piquemal, Jean-Philip; Sponer, Jiri
2015-07-30
Until now, atomistic simulations of DNA and RNA and their complexes have been executed using well calibrated but conceptually simple pair-additive empirical potentials (force fields). Although such simulations provided many valuable results, it is well established that simple force fields also introduce errors into the description, underlying the need for development of alternative anisotropic, polarizable molecular mechanics (APMM) potentials. One of the most abundant forces in all kinds of nucleic acids topologies is base stacking. Intra- and interstrand stacking is assumed to be the most essential factor affecting local conformational variations of B-DNA. However, stacking also contributes to formation of all kinds of noncanonical nucleic acids structures, such as quadruplexes or folded RNAs. The present study focuses on 14 stacked cytosine (Cyt) dimers and the doubly H-bonded dimer. We evaluate the extent to which an APMM procedure, SIBFA, could account quantitatively for the results of high-level quantum chemistry (QC) on the total interaction energies, and the individual energy contributions and their nonisotropic behaviors. Good agreements are found at both uncorrelated HF and correlated DFT and CCSD(T) levels. Resorting in SIBFA to distributed QC multipoles and to an explicit representation of the lone pairs is essential to respectively account for the anisotropies of the Coulomb and of the exchange-repulsion QC contributions.
The theory of intermolecular forces
Stone, Anthony J
2013-01-01
The theory of intermolecular forces has advanced very greatly in recent years. It has become possible to carry out accurate calculations of intermolecular forces for molecules of useful size, and to apply the results to important practical applications such as understanding protein structure and function, and predicting the structures of molecular crystals. The Theory of Intermolecular Forces sets out the mathematical techniques that are needed to describe and calculate intermolecular interactions and to handle the more elaborate mathematical models. It describes the methods that are used to calculate them, including recent developments in the use of density functional theory and symmetry-adapted perturbation theory. The use of higher-rank multipole moments to describe electrostatic interactions is explained in both Cartesian and spherical tensor formalism, and methods that avoid the multipole expansion are also discussed. Modern ab initio perturbation theory methods for the calculation of intermolecular inte...
Strong spin Seebeck effect in Kondo T-shaped double quantum dots
Wójcik, K. P.; Weymann, I.
2017-02-01
We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads’ spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.
Analysis of hydrocarbon chain conformation using double quantum coherence /sup 13/C NMR
Energy Technology Data Exchange (ETDEWEB)
Phillippi, M.A. (Clorox Technical Center, Pleasanton, CA); Wiersema, R.J.; Brainard, J.R.; London, R.E.
1982-12-15
The recent development of a double quantum coherence method for the observation of /sup 13/C-/sup 13/C scalar coupling constants without the need for isotopic labeling provides an alternative approach to the hydrocarbon chain conformation problem. The method is particularly suitable for this application since one-, two-, and three-bond carbon-carbon coupling constant values in hydrocarbons are typically of significantly different magnitudes, and observation of coupling constants of selected magnitude may be enhanced by the appropriate choice of pulse intervals. Consequently, J/sub CC/ values, which are dependent on the subtended dihedral angle, can be selectively observed. In order to evaluate the potential of this approach, studies on a 90% octanol-10% benzene-d/sub 6/ solution, with the latter serving for the deuterium lock were carried out. A representative /sup 13/C double quantum coherence spectrum of the region containing the octanol C-7 resonances with pulse intervals chosen to optimize couplings with magnitude close to 4.0 Hz is illustrated.
STRUCTURAL STUDIES OF BIOMATERIALS USING DOUBLE-QUANTUM SOLID-STATE NMR SPECTROSCOPY
Energy Technology Data Exchange (ETDEWEB)
Drobny, Gary P.; Long, J. R.; Karlsson, T.; Shaw, Wendy J.; Popham, Jennifer M.; Oyler, N.; Bower, Paula M.; Stringer, J.; Gregory, D.; Mehta, M.; Stayton, Patrick S.
2004-10-31
Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composites technologies. Here, we describe both the theory and practice of double-quantum solid-stateNMR(ssNMR) structure-determination techniques, as they are used to determine the secondary structures of surface-adsorbed peptides and proteins. In particular, we have used ssNMR dipolar techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Here, we also review NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. The adsorption or covalent attachment of biological macromolecules onto polymer materials to improve their biocompatibility has been pursued using a variety of approaches, but key to understanding their efficacy is the verification of the structure and dynamics of the immobilized biomolecules using double-quantum ssNMR spectroscopy.
Electron-nuclear interaction in 13C nanotube double quantum dots
Churchill, H. O. H.; Bestwick, A. J.; Harlow, J. W.; Kuemmeth, F.; Marcos, D.; Stwertka, C. H.; Watson, S. K.; Marcus, C. M.
2009-05-01
For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource enabling storage and retrieval of quantum information. To investigate the effect of a controllable nuclear environment on the evolution of confined electron spins, we have fabricated and measured gate-defined double quantum dots with integrated charge sensors made from single-walled carbon nanotubes with a variable concentration of 13C (nuclear spin I=1/2) among the majority zero-nuclear-spin 12C atoms. We observe strong isotope effects in spin-blockaded transport, and from the magnetic field dependence estimate the hyperfine coupling in 13C nanotubes to be of the order of 100μeV, two orders of magnitude larger than anticipated. 13C-enhanced nanotubes are an interesting system for spin-based quantum information processing and memory: the 13C nuclei differ from those in the substrate, are naturally confined to one dimension, lack quadrupolar coupling and have a readily controllable concentration from less than one to 105 per electron.
InGaAsP/InP Double Quantum Well Intermixing Induced by Phosphorus Ion Implantation
Institute of Scientific and Technical Information of China (English)
CHEN Jie; ZHAO Jie; WANG Yong-chen; HAN De-jun
2005-01-01
A quantum well intermixing(QWI) investigation on double quantum well(DQW) structure with two different emitting wavelength caused by phosphorus ion implantation and following rapid thermal annealing (RTA) was carried out by means of photoluminescence(PL). The ion implantation was performed at the energy of 120 kev with the dose ranging from 1 × 1011 cm-2 to 1× 1014 cm-2. The RTA was performed at the temperature of 700 ℃ for 30 s under pure nitrogen protection. The PL measurement implied that the band gap blue-shift from the upper well increases with the ion dose faster than that from lower well and the PL peaks from both QWs remained well separated under the lower dose implantation(～1×1011 cm-2 ) indicating that the implant vacancy distribution affects the QWI. When the ion dose is over ～ 1 × 1012 cm-2 , the band gap blue-shift from both wells increases with the ion dose and finally the two peaks merge together as one peak indicating the ion implantation caused a total intermixing of both quantum wells.
Sato, Kazuo; Nakazawa, Shigeki; Rahimi, Robabeh D.; Nishida, Shinsuke; Ise, Tomoaki; Shimoi, Daisuke; Toyota, Kazuo; Morita, Yasushi; Kitagawa, Masahiro; Carl, Parick; Höfner, Peter; Takui, Takeji
2009-06-01
Electrons with the spin quantum number 1/2, as physical qubits, have naturally been anticipated for implementing quantum computing and information processing (QC/QIP). Recently, electron spin-qubit systems in organic molecular frames have emerged as a hybrid spin-qubit system along with a nuclear spin-1/2 qubit. Among promising candidates for QC/QIP from the materials science side, the reasons for why electron spin-qubits such as molecular spin systems, i.e., unpaired electron spins in molecular frames, have potentialities for serving for QC/QIP will be given in the lecture (Chapter), emphasizing what their advantages or disadvantages are entertained and what technical and intrinsic issues should be dealt with for the implementation of molecular-spin quantum computers in terms of currently available spin manipulation technology such as pulse-based electron-nuclear double resonance (pulsed or pulse ENDOR) devoted to QC/QIP. Firstly, a general introduction and introductory remarks to pulsed ENDOR spectroscopy as electron-nuclear spin manipulation technology is given. Super dense coding (SDC) experiments by the use of pulsed ENDOR are also introduced to understand differentiating QC ENDOR from QC NMR based on modern nuclear spin technology. Direct observation of the spinor inherent in an electron spin, detected for the first time, will be shown in connection with the entanglement of an electron-nuclear hybrid system. Novel microwave spin manipulation technology enabling us to deal with genuine electron-electron spin-qubit systems in the molecular frame will be introduced, illustrating, from the synthetic strategy of matter spin-qubits, a key-role of the molecular design of g-tensor/hyperfine-(A-)tensor molecular engineering for QC/QIP. Finally, important technological achievements of recently-emerging CD ELDOR (Coherent-Dual ELectron-electron DOuble Resonance) spin technology enabling us to manipulate electron spin-qubits are described.
Biebricher, Andreas; Wende, Wolfgang; Escudé, Christophe; Pingoud, Alfred; Desbiolles, Pierre
2009-01-01
Fluorescence microscopy provides a powerful method to directly observe single enzymes moving along a DNA held in an extended conformation. In this work, we present results from single EcoRV enzymes labeled with quantum dots which interact with DNA manipulated by double optical tweezers. The application of quantum dots facilitated accurate enzyme tracking without photobleaching whereas the tweezers allowed us to precisely control the DNA extension. The labeling did not affect the biochemical a...
Energy Technology Data Exchange (ETDEWEB)
Das, S.; Nayak, R.K.; Sahu, T., E-mail: tsahu_bu@rediffmail.com; Panda, A.K.
2015-11-01
We study the effect of coupling of subband wave functions on the multisubband electron mobility in a barrier delta doped GaAs/Al{sub x}Ga{sub 1−x}As asymmetric double quantum well structure. We use selfconsistent solution of the coupled Schrödinger equation and Poisson's equation to calculate the subband wave functions and energy levels. The low temperature mobility is considered by using scatterings due to ionized impurities, interface roughness and alloy disorder. We show that variation of the width of the central barrier considerably affect the interplay of different scattering mechanisms on electron mobility through intersubband effects. Under single subband occupancy, the mobility increases with decrease in the barrier width as functions of doping concentration as well as function of well width. However, in case of double subband occupancy, effect of intersubband interaction yields opposite trend, i.e., increase in mobility with increase in barrier width. It is gratifying to show that in case of asymmetric variation of well widths the mobility shows nonmonotonic behavior which varies with change in the width of the central barrier under double subband occupancy.
Energy Technology Data Exchange (ETDEWEB)
Baba, Shoji, E-mail: baba@meso.t.u-tokyo.ac.jp; Sailer, Juergen [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Deacon, Russell S. [Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); RIKEN Advanced Science Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Oiwa, Akira [The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Shibata, Kenji [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Department of Electronics and Intelligent Systems, Tohoku Institute of Technology, Sendai 982-8577 (Japan); Hirakawa, Kazuhiko [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); JST CREST, 4-1-8 Hon-cho, Kawaguchi-shi, Saitama 332-0012 (Japan); Tarucha, Seigo [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); INQIE, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); QPEC, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656 (Japan)
2015-11-30
We report conductance and supercurrent measurements for InAs single and parallel double quantum dot Josephson junctions contacted with Nb or NbTiN superconducting electrodes. Large superconducting gap energy, high critical field, and large switching current are observed, all reflecting the features of Nb-based electrodes. For the parallel double dots, we observe an enhanced supercurrent when both dots are on resonance, which may reflect split Cooper pair tunneling.
Energy Technology Data Exchange (ETDEWEB)
Tagliaferri, M.L.V., E-mail: marco.tagliaferri@mdm.imm.cnr.it [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, 20125 Milano (Italy); Crippa, A. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, 20125 Milano (Italy); De Michielis, M. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Mazzeo, G.; Fanciulli, M. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, 20125 Milano (Italy); Prati, E. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Istituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)
2016-03-11
We report on the fabrication and the characterization of a tunable complementary-metal oxide semiconductor (CMOS) system consisting of two quantum dots and a MOS single electron transistor (MOSSET) charge sensor. By exploiting a compact T-shaped design and few gates fabricated by electron beam lithography, the MOSSET senses the charge state of either a single or double quantum dot at 4.2 K. The CMOS compatible fabrication process, the simplified control over the number of quantum dots and the scalable geometry make such architecture exploitable for large scale fabrication of multiple spin-based qubits in circuital quantum information processing. - Highlights: • Charge sensing of tunable, by position and number, quantum dots is demonstrated. • A compact T-shaped design with five gates at a single metalization level is proposed. • The electrometer is a silicon-etched nanowire acting as a disorder tolerant MOSSET.
Effects of Magnetic Field on the Valence Bond Property of the Double-Quantum-Dot Molecule
Institute of Scientific and Technical Information of China (English)
王立民; 罗莹; 马本堃
2002-01-01
The effects of the magnetic field on the valence bond property of the double-quantum-dot molecule are numerically studied by the finite element method and perturbation approach because of the absence of cylindrical symmetry in the horizontally coupled dots. The calculation results show that the energy value of the ground state changes differently from that of the first excited state with increasing magnetic field strength, and they cross under a certain magnetic field. The increasing magnetic field makes the covalent bond state change into an ionic bond state, which agrees qualitatively with experimental results and makes ionic bond states remain. The oscillator strength of transition between covalent bond states decreases distinctly with the increasing magnetic field strength, when the molecule is irradiated by polarized light. Such a phenomenon is possibly useful for actual applications.
THz Acoustic Spectroscopy by using Double Quantum Wells and Ultrafast Optical Spectroscopy
Wei, Fan Jun; Yeh, Yu-Hsiang; Sheu, Jinn-Kong; Lin, Kung-Hsuan
2016-06-01
GaN is a pivotal material for acoustic transducers and acoustic spectroscopy in the THz regime, but its THz phonon properties have not been experimentally and comprehensively studied. In this report, we demonstrate how to use double quantum wells as a THz acoustic transducer for measuring generated acoustic phonons and deriving a broadband acoustic spectrum with continuous frequencies. We experimentally investigated the sub-THz frequency dependence of acoustic attenuation (i.e., phonon mean-free paths) in GaN, in addition to its physical origins such as anharmonic scattering, defect scattering, and boundary scattering. A new upper limit of attenuation caused by anharmonic scattering, which is lower than previously reported values, was obtained. Our results should be noteworthy for THz acoustic spectroscopy and for gaining a fundamental understanding of heat conduction.
Courtney, Joseph M; Rienstra, Chad M
2016-08-01
We present a systematic study of dipolar double quantum (DQ) filtering in (13)C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n⩾7, provided that the (13)C nutation frequency is on the order of 100kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between (13)C and (1)H fields. For (13)C nutation frequencies greater than 75kHz, optimal performance is observed without an applied (1)H field. At spinning rates exceeding 20kHz, symmetry conditions as low as n=3 were found to perform adequately.
Spin Accumulation in a Double Quantum Dot Aharonov-Bohm Interferometer
Institute of Scientific and Technical Information of China (English)
YIN Hai-Tao; L(U) Tian-Quan; LIU Xiao-Jie; XUE Hui-Jie
2009-01-01
@@ We investigate the spin accumulation in a double quantum dot Aharonov-Bohm (AB) interferometer in which both the Rashba spin-orbit (RSO) interaction and intradot Coulomb interaction are taken into account. Due to the existence of the RSO interaction, the electron, flowing through different arms of the AB ring, will acquire a spin-dependent phase factor in the tunnel-coupling strengths. This phase factor will induce various interesting interference phenomena. It is found that the electrons of the different spin directions can accumulate in the two dots by properly adjusting the bias and the intradot level with a fixed RSO interaction strength. Moreover, both the magnitude and direction of the spin accumulation in each dot can be conveniently controlled and tuned by the gate voltage acting on the dot or the bias on the lead.
6j symbols for the modular double, quantum hyperbolic geometry, and supersymmetric gauge theories
Energy Technology Data Exchange (ETDEWEB)
Teschner, J.; Vartanov, G.S.
2012-02-15
We revisit the definition of the 6j-symbols from the modular double of U{sub q}(sl(2,R)), referred to as b-6j symbols. Our new results are (i) the identification of particularly natural normalization conditions, and (ii) new integral representations for this object. This is used to briefly discuss possible applications to quantum hyperbolic geometry, and to the study of certain supersymmetric gauge theories. We show, in particular, that the b-6j symbol has leading semiclassical asymptotics given by the volume of a non-ideal tetrahedron. We furthermore observe a close relation with the problem to quantize natural Darboux coordinates for moduli spaces of flat connections on Riemann surfaces related to the Fenchel-Nielsen coordinates. Our new integral representations finally indicate a possible interpretation of the b-6j symbols as partition functions of three-dimensional N=2 supersymmetric gauge theories. (orig.)
Dynamical behaviors of an exciton in an asymmetric double coupled quantum dot
Institute of Scientific and Technical Information of China (English)
LIU Can-de; LIU Wen; LI Feng-ling; WU Da-peng; SU Xi-yu
2006-01-01
Dynamical behaviors of an exciton in an asymmetric double coupled quantum dot and an altematingcurrent (ac) electric field have been analyzed based on the two-level approximation theory,and the conditions under which dynamical localization occurs are obtained.It shows that when the amplitude of the ac electric field is small,the Coulomb interaction plays an important role.The dynamical behaviors of the exciton are mainly confined in the low-level subspace.When the ratio of the field intensity to frequency is the root of Bessel function,electron and hole are localized in one dot,and they can be divided with the increasing amplitude of the ac electric field.
Optical phonon lasing and its detection in transport through semiconduc- tor double quantum dots
Okuyama, Rin; Eto, Mikio; Brandes, Tobias
2014-03-01
We theoretically propose optical phonon lasing for a double quantum dot (DQD) fabricated in a semiconductor substrate. No additional cavity or resonator is required. We show that the DQD couples to only two phonon modes that act as a natural cavity. The pumping to the upper level is realized by an electric current through the DQD under a finite bias. Using the rate equation in the Born-Markov-Secular approximation, we analyze the enhanced phonon emission when the level spacing in the DQD is tuned to the phonon energy. We find the phonon lasing when the pumping rate is much larger than the phonon decay rate, whereas anti-bunching of phonon emission is observed when the pumping rate is smaller.[1] Our theory can be also applicable to DQDs embedded in nanomechanical resonators to control the vibrating modes. We discuss detection of amplified modes using the electric current and its noise through the DQD, and another DQD fabricated nearby.
6j symbols for the modular double, quantum hyperbolic geometry, and supersymmetric gauge theories
Teschner, J
2012-01-01
We revisit the definition of the 6j-symbols from the modular double of U_q(sl(2,R)), referred to as b-6j symbols. Our new results are (i) the identification of particularly natural normalization conditions, and (ii) new integral representations for this object. This is used to briefly discuss possible applications to quantum hyperbolic geometry, and to the study of certain supersymmetric gauge theories. We show, in particular, that the b-6j symbol has leading semiclassical asymptotics given by the volume of a non-ideal tetrahedron. We furthermore observe a close relation with the problem to quantize natural Darboux coordinates for moduli spaces of flat connections on Riemann surfaces related to the Fenchel-Nielsen coordinates. Our new integral representations finally indicate a possible interpretation of the b-6j symbols as partition functions of three-dimensional N=2 supersymmetric gauge theories.
Phase Diagram of the Bose Condensation of Interwell Excitons in GaAs/AlGaAs Double Quantum Wells
DEFF Research Database (Denmark)
Dremin, A. A.; Timofeev, V. B.; Larionov, A. V.
2002-01-01
The luminescence of interwell excitons in GaAs/AlGaAs double quantum wells (n–i–n heterostructures) with large-scale fluctuations of random potential in the heteroboundary planes was studied at low temperatures down to 0.5 K. The properties of excitons whose photoexcited electron and hole...
Coupled-Double-Quantum-Dot Environmental Information Engines: A Numerical Analysis
Tanabe, Katsuaki
2016-06-01
We conduct numerical simulations for an autonomous information engine comprising a set of coupled double quantum dots using a simple model. The steady-state entropy production rate in each component, heat and electron transfer rates are calculated via the probability distribution of the four electronic states from the master transition-rate equations. We define an information-engine efficiency based on the entropy change of the reservoir, implicating power generators that employ the environmental order as a new energy resource. We acquire device-design principles, toward the realization of corresponding practical energy converters, including that (1) higher energy levels of the detector-side reservoir than those of the detector dot provide significantly higher work production rates by faster states' circulation, (2) the efficiency is strongly dependent on the relative temperatures of the detector and system sides and becomes high in a particular Coulomb-interaction strength region between the quantum dots, and (3) the efficiency depends little on the system dot's energy level relative to its reservoir but largely on the antisymmetric relative amplitudes of the electronic tunneling rates.
Mobility modulation in inverted delta doped coupled double quantum well structure
Sahoo, N.; Sahu, T.
2016-10-01
We have studied the modulation of electron mobility μ as a function of the electric field perpendicular to the interface plane Fp in a GaAs/AlGaAs double quantum well structure near the resonance of subband states. The functional dependence of μ on Fp exhibits a minimum near the anticrossing of subband states leading to an oscillatory behavior of μ. We show that the oscillatory enhancement of μ becomes more pronounced with increase in the difference between the doping concentrations in the side barriers. The oscillation of μ also increases by varying the widths of the two wells through shifting of the position of the middle barrier. It is interesting to show that the oscillation of μ is always larger when there is doping in barrier towards the substrate side compared to that of the surface side due to the difference in the influence of the interface roughness scattering potential. Further, broadening of the central barrier width increases the peaks of the oscillation of μ mostly due to the changes in the ionized impurity scattering potential. Our results can be utilized for the performance enhancement of quantum well field effect transistor devices.
Mobility modulation in inverted delta doped coupled double quantum well structure
Energy Technology Data Exchange (ETDEWEB)
Sahoo, N. [Department of Electronic Science, Berhampur University, 760007, Odisha (India); Sahu, T., E-mail: tsahu_bu@rediffmail.com [Department of Electronics and Communication Engineering, National Institute of Science and Technology, Palur Hills, Berhampur 761008, Odisha (India)
2016-10-01
We have studied the modulation of electron mobility μ as a function of the electric field perpendicular to the interface plane F{sub p} in a GaAs/AlGaAs double quantum well structure near the resonance of subband states. The functional dependence of μ on F{sub p} exhibits a minimum near the anticrossing of subband states leading to an oscillatory behavior of μ. We show that the oscillatory enhancement of μ becomes more pronounced with increase in the difference between the doping concentrations in the side barriers. The oscillation of μ also increases by varying the widths of the two wells through shifting of the position of the middle barrier. It is interesting to show that the oscillation of μ is always larger when there is doping in barrier towards the substrate side compared to that of the surface side due to the difference in the influence of the interface roughness scattering potential. Further, broadening of the central barrier width increases the peaks of the oscillation of μ mostly due to the changes in the ionized impurity scattering potential. Our results can be utilized for the performance enhancement of quantum well field effect transistor devices.
Waiting time distribution revealing the internal spin dynamics in a double quantum dot
Ptaszyński, Krzysztof
2017-07-01
Waiting time distribution and the zero-frequency full counting statistics of unidirectional electron transport through a double quantum dot molecule attached to spin-polarized leads are analyzed using the quantum master equation. The waiting time distribution exhibits a nontrivial dependence on the value of the exchange coupling between the dots and the gradient of the applied magnetic field, which reveals the oscillations between the spin states of the molecule. The zero-frequency full counting statistics, on the other hand, is independent of the aforementioned quantities, thus giving no insight into the internal dynamics. The fact that the waiting time distribution and the zero-frequency full counting statistics give a nonequivalent information is associated with two factors. Firstly, it can be explained by the sensitivity to different timescales of the dynamics of the system. Secondly, it is associated with the presence of the correlation between subsequent waiting times, which makes the renewal theory, relating the full counting statistics and the waiting time distribution, no longer applicable. The study highlights the particular usefulness of the waiting time distribution for the analysis of the internal dynamics of mesoscopic systems.
Aminophosphines: A Double Role in the Synthesis of Colloidal Indium Phosphide Quantum Dots.
Tessier, Mickael D; De Nolf, Kim; Dupont, Dorian; Sinnaeve, Davy; De Roo, Jonathan; Hens, Zeger
2016-05-11
Aminophosphines have recently emerged as economical, easy-to-implement precursors for making InP nanocrystals, which stand out as alternative Cd-free quantum dots for optoelectronic applications. Here, we present a complete investigation of the chemical reactions leading to InP formation starting from InCl3 and tris(dialkylamino)phosphines. Using nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction, we demonstrate that injection of the aminophosphine in the reaction mixture is followed by a transamination with oleylamine, the solvent of the reaction. In addition, mass spectrometry and NMR indicate that the formation of InP concurs with that of tetra(oleylamino)phosphonium chloride. The chemical yield of the InP formation agrees with this 4 P(+III) → P(-III) + 3 P(+V) disproportionation reaction occurring, since full conversion of the In precursor was only attained for a 4:1 P/In ratio. Hence it underlines the double role of the aminophosphine as both precursor and reducing agent. These new insights will guide further optimization of high quality InP quantum dots and might lead to the extension of synthetic protocols toward other pnictide nanocrystals.
Blockade in a silicon double quantum dot via the valley degree of freedom
Perron, Justin; Gullans, Michael J.; Taylor, Jacob M.; Stewart, M. D., Jr.; Zimmerman, Neil M.
Measuring electrical transport through double quantum dots (DQDs) is a useful way of illuminating several aspects of the states of the carriers. We show transport measurements through a silicon DQD formed in a mesa etched nanowire. Comparing the data at positive and negative bias voltage we observe a size asymmetry in the region of allowed current typically associated with Pauli spin blockade (PSB). However, the qualitative features of the asymmetry in our data, including i) lack of odd/even filling, ii) same polarity of asymmetry across many bias triangles, iii) lack of systematic dependence on magnetic field, and iv) a dependence on gate voltages, are all in disagreement with the predictions of PSB. In contrast, we have developed a model based on the selective filling of valley states in the DQD and the conservation of the valley degree of freedom during tunneling that predicts all of the qualitative features in our data. Joint Quantum Institute, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.
Double Chains Quantum Genetic Algorithm%链式双链量子遗传算法
Institute of Scientific and Technical Information of China (English)
陈吕强
2014-01-01
Aiming at the problem that the double chains quantum genetic algorithm has low conver-gence rate and is easy to fall into local optimum value, a new quantum genetic algorithm is proposed. In this algorithm, the population is divided into several groups, and there exists a common member between the two neighboring groups. For example, the last member of the ith group is also the first member of the (i+1)th group. All the members of the same group are updated in the same direction with the same step. At the same time, through the common member, the neighboring groups keep pace with one another. This method can reduce the time complexity, maintain the population diversity, and avoid making the algorithm fall into the local optimum value. The simulation results show that the algorithm is much more efficient in the optimization of complex functions than double chains quantum genetic algorithm.%针对双链量子遗传算法具有收敛速度慢，容易陷入局部最优解等问题，提出一种新的双链量子遗传算法。该算法将种群个体分组，相邻组间有一个共有个体，即第i组的最后一条染色体同时是第i+1组的第一个个体。组内各染色体同方向同步长更新，相邻组间通过共有个体保持组间同步。该方法能很好地降低算法时间复杂度，保持种群个体的多样性，从而避免算法陷入局部最优值。最后通过实验验证该算法对复杂函数的优化结果明显优于双链量子遗传算法。
SU(4)-SU(2) crossover and spin-filter properties of a double quantum dot nanosystem
Lopes, V.; Padilla, R. A.; Martins, G. B.; Anda, E. V.
2017-06-01
The SU(4)-SU(2) crossover, driven by an external magnetic field h , is analyzed in a capacitively coupled double quantum dot device connected to independent leads. As one continuously charges the dots from empty to quarter filled, by varying the gate potential Vg, the crossover starts when the magnitude of the spin polarization of the double quantum dot, as measured by - , becomes finite. Although the external magnetic field breaks the SU(4) symmetry of the Hamiltonian, the ground state preserves it in a region of Vg, where - =0 . Once the spin polarization becomes finite, it initially increases slowly until a sudden change occurs, in which (polarization direction opposite to the magnetic field) reaches a maximum and then decreases to negligible values abruptly, at which point an orbital SU(2) ground state is fully established. This crossover from one Kondo state, with emergent SU(4) symmetry, where spin and orbital degrees of freedom all play a role, to another, with SU(2) symmetry, where only orbital degrees of freedom participate, is triggered by a competition between g μBh , the energy gain by the Zeeman-split polarized state and the Kondo temperature TKS U (4 ), the gain provided by the SU(4) unpolarized Kondo-singlet state. At fixed magnetic field, the knob that controls the crossover is the gate potential, which changes the quantum dots occupancies. If one characterizes the occurrence of the crossover by Vgmax, the value of Vg where reaches a maximum, one finds that the function f relating the Zeeman splitting, Bmax, which corresponds to Vgmax, i.e., Bmax=f (Vgmax) , has a similar universal behavior to that of the function relating the Kondo temperature to Vg. In addition, our numerical results show that near the SU(4) Kondo temperature and for relatively small magnetic fields the device has a ground state that restricts the electronic population at the dots to be spin polarized along the magnetic field. These two facts introduce very efficient spin
Perturbation analyses of intermolecular interactions
Koyama, Yohei M.; Kobayashi, Tetsuya J.; Ueda, Hiroki R.
2011-08-01
Conformational fluctuations of a protein molecule are important to its function, and it is known that environmental molecules, such as water molecules, ions, and ligand molecules, significantly affect the function by changing the conformational fluctuations. However, it is difficult to systematically understand the role of environmental molecules because intermolecular interactions related to the conformational fluctuations are complicated. To identify important intermolecular interactions with regard to the conformational fluctuations, we develop herein (i) distance-independent and (ii) distance-dependent perturbation analyses of the intermolecular interactions. We show that these perturbation analyses can be realized by performing (i) a principal component analysis using conditional expectations of truncated and shifted intermolecular potential energy terms and (ii) a functional principal component analysis using products of intermolecular forces and conditional cumulative densities. We refer to these analyses as intermolecular perturbation analysis (IPA) and distance-dependent intermolecular perturbation analysis (DIPA), respectively. For comparison of the IPA and the DIPA, we apply them to the alanine dipeptide isomerization in explicit water. Although the first IPA principal components discriminate two states (the α state and PPII (polyproline II) + β states) for larger cutoff length, the separation between the PPII state and the β state is unclear in the second IPA principal components. On the other hand, in the large cutoff value, DIPA eigenvalues converge faster than that for IPA and the top two DIPA principal components clearly identify the three states. By using the DIPA biplot, the contributions of the dipeptide-water interactions to each state are analyzed systematically. Since the DIPA improves the state identification and the convergence rate with retaining distance information, we conclude that the DIPA is a more practical method compared with the
Forming double layer-encapsulated quantum dots for bio-imaging and cell targeting
Fahmi, Mochamad Zakki; Chang, Jia-Yaw
2013-01-01
We report a simple and effective approach for the preparation of double layer-encapsulated quantum dots (DL-Qdots) composed of alkyl-capping ligands to interdigitate with hydrophobic, protective agents on the surface of AgInS2/ZnS quantum dots (Qdots), which allow phase transfer of hydrophobic Qdots from the organic phase into the aqueous phase. The alkyl-capping ligands consist of a hydrophobic, aliphatic chain and different functional terminal groups (e.g., carboxyl, amine, hydroxyl, and thiol groups) that can serve as reactive sites to chemically couple with other materials. The resulting DL-Qdots bearing various functional groups retain good fluorescence properties and show excellent solubility as well as stability over a range of pH in the aqueous phase. Cytotoxicity studies of DL-Qdots bearing carboxyl groups (DL-Qdots-COOH) were carried out against human cervical (HeLa) cancer cells to elicit no apparent toxicity even at high concentrations of 300 μg mL-1 and 24 h of incubation. To demonstrate their potential biomedical application, DL-Qdots-COOH were further conjugated with folate for staining in HeLa, human liver carcinoma (HepG2), and human breast (MCF-7) cancer cells. Confocal imaging characterization revealed that folate-conjugated DL-Qdots could target most specifically and effectively HeLa cells via folate receptor-mediated targeted delivery compared to HepG2 and MCF-7 cells. The generality and simplicity of this newly developed strategy can possibly be extended to a large variety of hydrophobic Qdots and nanocrystals whose surface protective agents have a long aliphatic chain.
Proton chemical shift tensors determined by 3D ultrafast MAS double-quantum NMR spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Zhang, Rongchun; Mroue, Kamal H.; Ramamoorthy, Ayyalusamy, E-mail: ramamoor@umich.edu [Biophysics and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055 (United States)
2015-10-14
Proton NMR spectroscopy in the solid state has recently attracted much attention owing to the significant enhancement in spectral resolution afforded by the remarkable advances in ultrafast magic angle spinning (MAS) capabilities. In particular, proton chemical shift anisotropy (CSA) has become an important tool for obtaining specific insights into inter/intra-molecular hydrogen bonding. However, even at the highest currently feasible spinning frequencies (110–120 kHz), {sup 1}H MAS NMR spectra of rigid solids still suffer from poor resolution and severe peak overlap caused by the strong {sup 1}H–{sup 1}H homonuclear dipolar couplings and narrow {sup 1}H chemical shift (CS) ranges, which render it difficult to determine the CSA of specific proton sites in the standard CSA/single-quantum (SQ) chemical shift correlation experiment. Herein, we propose a three-dimensional (3D) {sup 1}H double-quantum (DQ) chemical shift/CSA/SQ chemical shift correlation experiment to extract the CS tensors of proton sites whose signals are not well resolved along the single-quantum chemical shift dimension. As extracted from the 3D spectrum, the F1/F3 (DQ/SQ) projection provides valuable information about {sup 1}H–{sup 1}H proximities, which might also reveal the hydrogen-bonding connectivities. In addition, the F2/F3 (CSA/SQ) correlation spectrum, which is similar to the regular 2D CSA/SQ correlation experiment, yields chemical shift anisotropic line shapes at different isotropic chemical shifts. More importantly, since the F2/F1 (CSA/DQ) spectrum correlates the CSA with the DQ signal induced by two neighboring proton sites, the CSA spectrum sliced at a specific DQ chemical shift position contains the CSA information of two neighboring spins indicated by the DQ chemical shift. If these two spins have different CS tensors, both tensors can be extracted by numerical fitting. We believe that this robust and elegant single-channel proton-based 3D experiment provides useful atomistic
Enhanced performance of InGaN/GaN multiple quantum well solar cells with double indium content
Institute of Scientific and Technical Information of China (English)
Zhao Bi-Jun; Chen Xin; Ren Zhi-Wei; Tong Jin-Hui; Wang Xing-Fu; Li Dan-Wei; Zhuo Xiang-Jing
2013-01-01
The performance of a multiple quantum well (MQW) InGaN solar cell with double indium content is investigated.It is found that the adoption of a double indium structure can effectively broaden the spectral response of the external quantum efficiencies and optimize the overall performance of the solar cell.Under AM1.5G illumination,the short-circuit current density (Jsc) and conversion efficiency of the solar cell are enhanced by 65％ and 13％ compared with those of a normal single-indium-content MQW solar cell.These improvements are mainly attributed to the expansion of the absorption spectrum and better extraction efficiency of the photon-generated carriers induced by higher polarization.
A Convergent Iterative Solution of the Quantum Double-well Potential
Friedberg, R; Zhao Wei Qin; Cimenser, A
2001-01-01
We present a new convergent iterative solution for the two lowest quantum wave functions $\\psi_{ev}$ and $\\psi_{od}$ of the Hamiltonian with a quartic double well potential $V$ in one dimension. By starting from a trial function, which is by itself the exact lowest even or odd eigenstate of a different Hamiltonian with a modified potential $V+\\delta V$, we construct the Green's function for the modified potential. The true wave functions, $\\psi_{ev}$ or $\\psi_{od}$, then satisfies a linear inhomogeneous integral equation, in which the inhomogeneous term is the trial function, and the kernel is the product of the Green's function times the sum of $\\delta V$, the potential difference, and the corresponding energy shift. By iterating this equation we obtain successive approximations to the true wave function; furthermore, the approximate energy shift is also adjusted at each iteration so that the approximate wave function is well behaved everywhere. We are able to prove that this iterative procedure converges fo...
Electro-acoustic solitary waves and double layers in a quantum plasma
Dip, P. R.; Hossen, M. A.; Salahuddin, M.; Mamun, A. A.
2017-02-01
A meticulous theoretical investigation has carried out to study the properties related to the higher-order nonlinearity of the electro-acoustic waves, specifically ion-acoustic (IA) waves in an unmagnetized, collisionless, quantum electron-positron-ion (EPI) plasma. The plasma system is supposed to be formed of positively charged inertial heavy ions, inertialess electrons and positrons. The reductive perturbation technique is employed to derive the modified Korteweg-de Vries (mK-dV) equation to analyze the solitary waves (SWs), and the standard Gardner (SG) equation to analyze the higher-order SWs as well as double layers (DLs). The basic features (viz. amplitude, width, phase speed, etc.) of the IA SWs and DLs are examined. The comparison between the mK-dV SWs and SG SWs is also made. It is found that the amplitude, width, phase speed, etc. of the IA SWs and DLs are significantly modified by the effects of the both Fermi temperatures as well as pressures and Bohm potentials of electrons and positrons. Our findings may be useful in explaining the physics behind the formation of the IA waves in both astrophysical and laboratory EPI plasmas (viz. white dwarfs, laser-solid matter interaction experiments, etc.).
Quantum dots-based double-color imaging of HER2 positive breast cancer invasion
Energy Technology Data Exchange (ETDEWEB)
Liu, Xiu-Li, E-mail: usually.158@163.com [Department of Oncology, Zhongnan Hospital of Wuhan University, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Hubei Key Laboratory of Tumor Biological Behaviors and Hubei Cancer Clinical Study Center, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Peng, Chun-Wei, E-mail: pqc278@163.com [Department of Oncology, Zhongnan Hospital of Wuhan University, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Hubei Key Laboratory of Tumor Biological Behaviors and Hubei Cancer Clinical Study Center, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Chen, Chuang, E-mail: chenc2469@163.com [Department of Oncology, Zhongnan Hospital of Wuhan University, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Hubei Key Laboratory of Tumor Biological Behaviors and Hubei Cancer Clinical Study Center, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Yang, Xue-Qin, E-mail: yxqjenny@126.com [Department of Oncology, Zhongnan Hospital of Wuhan University, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Hubei Key Laboratory of Tumor Biological Behaviors and Hubei Cancer Clinical Study Center, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Hu, Ming-Bai, E-mail: humingbai@126.com [Department of Oncology, Zhongnan Hospital of Wuhan University, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Hubei Key Laboratory of Tumor Biological Behaviors and Hubei Cancer Clinical Study Center, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Xia, He-Shun, E-mail: xiaheshun@yahoo.com.cn [Department of Pathology, Hubei Cancer Hospital, Wuhan, Hubei 430079 (China); Liu, Shao-Ping, E-mail: lsp_77@126.com [Department of Oncology, Zhongnan Hospital of Wuhan University, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); Hubei Key Laboratory of Tumor Biological Behaviors and Hubei Cancer Clinical Study Center, No 169 Donghu Road, Wuchang District, Wuhan 430071 (China); and others
2011-06-10
Highlights: {yields} HER2 level is closely related to the biologic behaviors of breast cancer cells. {yields} A new method to simultaneously image HER2 and type IV collagen was established. {yields} HER2 status and type IV collagen degradation predict breast cancer invasion. {yields} The complex interactions between tumor and its environment were revealed. -- Abstract: It has been well recognized that human epidermal growth factor receptor 2 (HER2) level in breast cancer (BC) is closely related to the malignant biologic behaviors of the tumor, including invasion and metastasis. Yet, there has been a lack of directly observable evidence to support such notion. Here we report a quantum dots (QDs)-based double-color imaging technique to simultaneously show the HER2 level on BC cells and the type IV collagen in the tumor matrix. In benign breast tumor, the type IV collagen was intact. With the increasing of HER2 expression level, there has been a progressive decrease in type IV collagen around the cancer nest. At HER2 (3+) expression level, there has virtually been a total destruction of type IV collagen. Moreover, HER2 (3+) BC cells also show direct invasion into the blood vessels. This novel imaging method provides direct observable evidence to support the theory that the HER2 expression level is directly related to BC invasion.
Impact of g -factors and valleys on spin qubits in a silicon double quantum dot
Hwang, J. C. C.; Yang, C. H.; Veldhorst, M.; Hendrickx, N.; Fogarty, M. A.; Huang, W.; Hudson, F. E.; Morello, A.; Dzurak, A. S.
2017-07-01
We define single electron spin qubits in a silicon metal-oxide-semiconductor double quantum dot system. By mapping the qubit resonance frequency as a function of a gate-induced electric field, the spectrum reveals an anticrossing that is consistent with an intervalley spin-orbit coupling. We fit the data from which we extract an intervalley coupling strength of 43 MHz. In addition, we observe a narrow resonance near the primary qubit resonance when we operate the device in the (1 ,1 ) charge configuration. The experimental data are consistent with a simulation involving two weakly exchanged-coupled spins with a Zeeman energy difference of 1 MHz, of the same order as the Rabi frequency. We conclude that the narrow resonance is the result of driven transitions between the T- and T+ triplet states, using an electron spin resonance signal of frequency located halfway between the resonance frequencies of the two individual spins. The findings presented here offer an alternative method of implementing two-qubit gates, of relevance to the operation of larger-scale spin qubit systems.
Baidya, Santu; Waghmare, Umesh V.; Paramekanti, Arun; Saha-Dasgupta, Tanusri
2016-10-01
Towards the goal of realizing topological phases in thin films of correlated oxide and heterostructures, we propose here a quantum anomalous Hall insulator (QAHI) in ultrathin films of double perovskites based on mixed 3 d -5 d or 3 d -4 d transition-metal ions, grown along the [111] direction. Considering the specific case of ultrathin Ba2FeReO6 , we present a theoretical analysis of an effective Hamiltonian derived from first principles. We establish that a strong spin-orbit coupling at the Re site, t2 g symmetry of the low-energy d bands, polarity of its [111] orientation of perovskite structure, and mixed 3 d -5 d chemistry results in room temperature magnetism with a robust QAHI state of Chern number C =1 and a large band gap. We uncover and highlight a nonrelativistic orbital Rashba-type effect in addition to the spin-orbit coupling, that governs this QAHI state. With a band gap of ˜100 meV in electronic structure and magnetic transition temperature Tc˜300 K estimated by Monte Carlo simulations, our finding of the QAHI state in ultrathin Ba2FeReO6 is expected to stimulate experimental verification along with possible practical applications of its dissipationless edge currents.
Magneto-transport studies of a few hole GaAs double quantum dot in tilted magnetic fields
Studenikin, Sergei; Bogan, Alex; Tracy, Lisa; Gaudreau, Louis; Sachrajda, Andy; Korkusinski, Marek; Reno, John; Hargett, Terry
Compared to equivalent electron devices, single-hole spins interact weakly with lattice nuclear spins leading to extended quantum coherence times. This makes p-type Quantum Dots (QD) particularly attractive for practical quantum devices such as qubit circuits, quantum repeaters, quantum sensors etc. where long coherence time is required. Another property of holes is the possibility to tune their g-factor as a result of the strong anisotropy of the valance band. Hole g-factors can be conveniently tuned in situ from a large value to almost zero by tilting the magnetic field relative to the 2D hole gas surface normal. In this work we explore high-bias magneto-transport properties of a p-type double quantum dot (DQD) device fabricated from a GaAs/AlGaAs heterostructures using lateral split-gate technology. A charge detection technique is used to monitor number of holes and tune the p-DQD in a single hole regime around (1,1) and (2,0) occupation states where Pauli spin-blockaded transport is expected. Four states are identified in quantizing magnetic fields within the high-bias current stripe - three-fold triplet and a singlet which allows determining effective heavy hole g-factor as a function of the tilt angle from 90 to 0 degrees.
Directory of Open Access Journals (Sweden)
A. Stockklauser
2017-03-01
Full Text Available The strong coupling limit of cavity quantum electrodynamics (QED implies the capability of a matterlike quantum system to coherently transform an individual excitation into a single photon within a resonant structure. This not only enables essential processes required for quantum information processing but also allows for fundamental studies of matter-light interaction. In this work, we demonstrate strong coupling between the charge degree of freedom in a gate-defined GaAs double quantum dot (DQD and a frequency-tunable high impedance resonator realized using an array of superconducting quantum interference devices. In the resonant regime, we resolve the vacuum Rabi mode splitting of size 2g/2π=238 MHz at a resonator linewidth κ/2π=12 MHz and a DQD charge qubit decoherence rate of γ_{2}/2π=40 MHz extracted independently from microwave spectroscopy in the dispersive regime. Our measurements indicate a viable path towards using circuit-based cavity QED for quantum information processing in semiconductor nanostructures.
Edén, Mattias
2010-05-01
Three two-dimensional (2D) NMR homonuclear correlation techniques invoking double-quantum (2Q) filtration of the central transitions of half-integer spins are evaluated numerically and experimentally. They correlate directly detected single-quantum (1Q) coherences in the t(2) domain with either of 1Q, two-spin 2Q or single-spin multiple-quantum coherence-evolutions in the indirect (t(1)) dimension. We employ experimental (23)Na and (27)Al NMR on sodium sulfite and the natural mineral sillimanite (SiAl(2)O(5)), in conjunction with simulated 2D spectra from pairs of dipolar-recoupled spins-3/2 and 5/2 at different external magnetic fields, to compare the correlation strategies from the viewpoints of 2D spectral resolution, signal sensitivity, implementational aspects and their relative merits for establishing internuclear proximities and quadrupolar tensor orientations.
On the relation between the modular double of U{sub q}(sl(2,R)) and the quantum Teichmueller theory
Energy Technology Data Exchange (ETDEWEB)
Nidaiev, Iurii; Teschner, Joerg
2013-02-15
We exhibit direct relations between the modular double of U{sub q}(sl(2,R)) and the quantum Teichmueller theory. Explicit representations for the fusion- and braiding operations of the quantum Teichmueller theory are immediate consequences. Our results include a simplified derivation of the Clebsch-Gordan decomposition for the principal series of representation of the modular double of U{sub q}(sl(2,R)).
Cong, G. W.; Akimoto, R.; Gozu, S.; Mozume, T.; Hasama, T.; Ishikawa, H.
2010-03-01
We demonstrated the intersubband absorption in undoped InGaAs/AlAsSb coupled double quantum wells through silicon ion implantation and rapid thermal annealing. For an implantation dose of 1×1014 cm-2, the actual carrier density of a sample annealed at 600 °C for 1 min was ˜7.5×1013 cm-2 (˜75% activation efficiency); the activation energy was ˜1.41 eV. The simultaneously generated quantum well intermixing (QWI) was nonuniform due to the silicon ion distribution. The effects of QWI nonuniformity on both intersubband and interband transitions were explained by eight-band k ṡp calculation. This study will open a route for monolithic integration of intersubband-transition-based high-speed all-optical switches.
Chen, Lixia; He, Fang; Sun, Zuwen; Zhang, Yan; Li, Fengjiao; Huang, Yuan; Gu, Ruisona
2015-02-01
Si single quantum dots (QDs) and Si/Ge double QDs doped TiO2 films were successfully fabricated via layer-by-layer ion beam sputtering assisted by annealing treatment, and their morphology and optical absorption performance were analyzed in this paper. TEM images show that Si QDs and Si/Ge double QDs prepared in the TiO2 matrix are in a uniform size distribution and high density, especially after annealed at 500 °C. XPS results indicate that Si in the TiO2 films mainly exists in the form of elemental Si and SiO2, and Ge is in elemental form. From the optical absorption spectra, the optical response of the TiO2 films is shifted from ultraviolet to visible and near infrared region when they are doped by the QDs, and the Si/Ge double QDs co-doped TiO2 films show better optical response compared with the Si QDs doped TiO2 films, suggesting a hybrid enhanced effect of double QDs.
Universal Set of Quantum Gates for Double-Dot Exchange-Only Spin Qubits Under Realistic Conditions
de Michielis, Marco; Ferraro, Elena; Rotta, Davide; Mazzeo, Giovanni; Tagliaferri, Marco; Crippa, Alessandro; Fanciulli, Marco; Prati, Enrico
2014-03-01
We report on a universal set of quantum logic gates for hybrid qubits. In a hybrid qubit the information is encoded in the spin state of three electrons elettrostatically confined in a silicon double quantum dot (QD), in (2,1) filling. All electrical operations, reduced fabrication complexity and high scalability are the strengths of this technology. Schrieffer-Wolff effective models for both one and two coupled hybrid qubit are developed including the inescapable exchange interaction between electrons in the same QD. Optimal sequences of exchange interactions creating a complete set of quantum operations, namely Hadamard, π/8 and CNOT gates, are obtained by using a search algorithm, based on simplex and genetic ones. Silicon devices have been designed by SDFT-based program and efforts in its fabrication have produced in-plane inter-QDs distances down to 100 nm by means of electron beam lithography. Double QDs devices operating in few electron filling regime have been preliminary characterized at 4.2 K. Second affiliation: DSM, Università degli Studi di Milano-Bicocca, Via Cozzi 53, I-20125 Milano, Italy.
Energy Technology Data Exchange (ETDEWEB)
Nayak, R. K.; Das, S.; Panda, A. K.; Sahu, T., E-mail: tsahu-bu@rediffmail.com [Department of Electronics and Communication Engineering, National Institute of Science and Technology, Palur Hills, Berhampur-761 008, Odisha (India)
2015-11-15
We show that sharp nonmonotic variation of low temperature electron mobility μ can be achieved in GaAs/Al{sub x}Ga{sub 1-x}As barrier delta-doped double quantum well structure due to quantum mechanical transfer of subband electron wave functions within the wells. We vary the potential profile of the coupled structure as a function of the doping concentration in order to bring the subbands into resonance such that the subband energy levels anticross and the eigen states of the coupled structure equally share both the wells thereby giving rise to a dip in mobility. When the wells are of equal widths, the dip in mobility occurs under symmetric doping of the side barriers. In case of unequal well widths, the resonance can be obtained by suitable asymmetric variation of the doping concentrations. The dip in mobility becomes sharp and also the wavy nature of mobility takes a rectangular shape by increasing the barrier width. We show that the dip in mobility at resonance is governed by the interface roughness scattering through step like changes in the subband mobilities. It is also gratifying to show that the drop in mobility at the onset of occupation of second subband is substantially supressed through the quantum mechanical transfer of subband wave functions between the wells. Our results can be utilized for performance enhancement of coupled quantum well devices.
Ting, David Z.-Y; Soibel, Alexander; Khoshakhlagh, Arezou; Keo, Sam A.; Nguyen, Jean; Hoglund, Linda; Mumolo, Jason M.; Liu, John K.; Rafol, Sir B.; Hill, Cory J.; Gunapala, Sarath D.
2012-01-01
The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from approximately 4.2 micrometers to 6 micrometers, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225 K.
Ting, David Z.-Y; Soibel, Alexander; Khoshakhlagh, Arezou; Keo, Sam A.; Nguyen, Jean; Hoglund, Linda; Mumolo, Jason M.; Liu, John K.; Rafol, Sir B.; Hill, Cory J.;
2012-01-01
The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from approximately 4.2 micrometers to 6 micrometers, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225 K.
Partial hybridisation of electron-hole states in an InAs/GaSb double quantum well heterostructure
Knox, C. S.; Morrison, C.; Herling, F.; Ritchie, D. A.; Newell, O.; Myronov, M.; Linfield, E. H.; Marrows, C. H.
2017-10-01
InAs/GaSb coupled quantum well heterostructures are important semiconductor systems with applications ranging from spintronics to photonics. Most recently, InAs/GaSb heterostructures have been identified as candidate two-dimensional topological insulators, predicted to exhibit helical edge conduction via fully spin-polarised carriers. We study an InAs/GaSb double quantum well heterostructure with an AlSb barrier to decouple partially the 2D electrons and holes, and find conduction consistent with a 2D hole gas, with an effective mass of 0.235 ± 0.005 m 0, existing simultaneously with hybridised carriers with an effective mass of 0.070 ± 0.005 m 0, where m 0 is the bare electron mass.
Accardi, Antonio; Barth, Ingo; Kühn, Oliver; Manz, Jörn
2010-10-28
Quantum dynamics simulations of double proton transfer (DPT) in the model porphine, starting from a nonequilibrium initial state, demonstrate that a switch from synchronous (or concerted) to sequential (or stepwise or successive) breaking and making of two bonds is possible. For this proof of principle, we employ the simple model of Smedarchina, Z.; Siebrand, W.; Fernández-Ramos, A. J. Chem. Phys. 2007, 127, 174513, with reasonable definition for the domains D for the reactant R, the product P, the saddle point SP2 which is crossed during synchronous DPT, and two intermediates I = I(1) + I(2) for two alternative routes of sequential DPT. The wavepacket dynamics is analyzed in terms of various properties, from qualitative conclusions based on the patterns of the densities and flux densities, until quantitative results for the time evolutions of the populations or probabilities P(D)(t) of the domains D = R, P, SP2, and I, and the associated net fluxes F(D)(t) as well as the domain-to-domain (DTD) fluxes F(D1,D2) between neighboring domains D1 and D2. Accordingly, the initial synchronous mechanism of the first forward reaction is due to the directions of various momenta, which are imposed on the wavepacket by the L-shaped part of the steep repulsive wall of the potential energy surface (PES), close to the minimum for the reactant. At the same time, these momenta cause initial squeezing followed by rapid dispersion of the representative wavepacket. The switch from the synchronous to sequential mechanism is called indirect, because it is mediated by two effects: First, the wavepacket dispersion; second, relief reflections of the broadened wavepacket from wide regions of the inverse L-shaped steep repulsive wall of the PES close to the minimum for the product, preferably to the domains I = I(1) + I(2) for the sequential DPT during the first back reaction, and also during the second forward reaction, etc. Our analysis also discovers a variety of minor effects, such as
Hatano, T; Kubo, T; Tokura, Y; Amaha, S; Teraoka, S; Tarucha, S
2011-02-18
Aharonov-Bohm (AB) oscillations are studied for a parallel-coupled vertical double quantum dot with a common source and drain electrode. We observe AB oscillations of current via a one-electron bonding state as the ground state and an antibonding state as the excited state. As the center gate voltage becomes more negative, the oscillation period is clearly halved for both the bonding and antibonding states, and the phase changes by half a period for the antibonding state. This result can be explained by a calculation that takes account of the indirect interdot coupling via the two electrodes.
Energy Technology Data Exchange (ETDEWEB)
Amaha, S., E-mail: s-amaha@riken.jp [Quantum Spin Information Project, Japan Science and Technology Agency, ICORP, 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan); Quantum Functional System Research Group, RIKEN Center for Emergent Matter Science, RIKEN, 3-1 Wako-shi, Saitama 351-0198 (Japan); Hatano, T. [Quantum Spin Information Project, Japan Science and Technology Agency, ICORP, 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan); Department of Physics, Tohoku University, Sendai-shi, Miyagi 980-8578 (Japan); Tarucha, S. [Quantum Spin Information Project, Japan Science and Technology Agency, ICORP, 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan); Quantum Functional System Research Group, RIKEN Center for Emergent Matter Science, RIKEN, 3-1 Wako-shi, Saitama 351-0198 (Japan); Department of Applied Physics, School of Engineering, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Gupta, J. A.; Austing, D. G. [National Research Council of Canada, M50, Montreal Road, Ottawa, Ontario K1A 0R6 (Canada)
2015-04-27
We investigate nuclear spin pumping with five-electron quadruplet spin states in a spin-blockaded weakly coupled vertical double quantum dot device. Two types of hysteretic steps in the leakage current are observed on sweeping the magnetic field and are associated with bidirectional polarization of nuclear spin. Properties of the steps are understood in terms of bias-voltage-dependent conditions for the mixing of quadruplet and doublet spin states by the hyperfine interaction. The hysteretic steps vanish when up- and down-nuclear spin pumping processes are in close competition.
Tang, Chi-Shung; Tseng, Shu-Ting; Gudmundsson, Vidar; Cheng, Shun-Jen
2015-03-04
We investigate double finger gate (DFG) controlled spin-resolved resonant transport properties in an n-type quantum channel with a Rashba-Zeeman (RZ) subband energy gap. By appropriately tuning the DFG in the strong Rashba coupling regime, resonant state structures in conductance can be found that are sensitive to the length of the DFG system. Furthermore, a hole-like bound state feature below the RZ gap and an electron-like quasi-bound state feature at the threshold of the upper spin branch can be found that is insensitive to the length of the DFG system.
Collective behavior of interwell excitons laterally confined in GaAs/AlGaAs double quantum wells
Energy Technology Data Exchange (ETDEWEB)
Timofeev, V.B.; Gorbunov, A.V. [Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation)
2005-02-01
The luminescence of interwell excitons laterally confined by long range potential fluctuations and with the use of inhomogeneous electric field in n-i-n GaAs/AlGaAs heterostructures double quantum wells has been investigated under variation of excitation power and temperature. Above mobility threshold very narrow interwell exciton line has been observed and its intensity decrease is linearly dependent on temperature growth. The observed phenomena, which were critical to exciton density and temperature, are attributed to the Bose-condensation in laterally confined quasi-two dimensional system of interwell excitons. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Coherent Transport Through a Quantum Dot Embedded in a Double-Slit-Like Aharonov-Bohm Ring
Institute of Scientific and Technical Information of China (English)
黄丽; 游建强; 颜晓红; 韦世豪
2002-01-01
Coherent transport through a quantum dot embedded in one arm ora double-slit-like Aharonov-Bohm (AB) ringis studied using the Green's function approach. We obtain experimental observations such as continuous phaseshift along a single resonance peak and sharp inter-resonance phase drop. The AB oscillations of the differentialconductance of the whole device are calculated by using the nonequilibrium Keldysh formalism. It is shown thatthe oscillating conductance has a continuous bias-voltage-dependent phase shift and is asymmetric in both linearand nonlinear response regimes.
Yesilgul, U.; Sari, H.; Ungan, F.; Martínez-Orozco, J. C.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.; Sökmen, I.
2017-03-01
In this study, the effects of electric and magnetic fields on the optical rectification and second and third harmonic generation in asymmetric double quantum well under the intense non-resonant laser field is theoretically investigated. We calculate the optical rectification and second and third harmonic generation within the compact density-matrix approach. The theoretical findings show that the influence of electric, magnetic, and intense laser fields leads to significant changes in the coefficients of nonlinear optical rectification, second and third harmonic generation.
DEFF Research Database (Denmark)
Larionov, A. V.; Timofeev, V. B.; Hvam, Jørn Märcher
2002-01-01
The time evolution and kinetics of photoluminescence (PL) spectra of interwell excitons in double GaAs/AlGaAs quantum wells (n–i–n structures) have been investigated under the pulse resonance excitation of intrawell 1sHH excitons using a pulsed tunable laser. It is found that the collective exciton......, and a significant increase in the radiative decay rate of the condensed phase. The collective exciton phase arises at temperatures T properties of the collective phase of interwell excitons and experimental manifestations of this coherence...
Spin blockade and coherent dynamics of high-spin states in a three-electron double quantum dot
Chen, Bao-Bao; Wang, Bao-Chuan; Cao, Gang; Li, Hai-Ou; Xiao, Ming; Guo, Guang-Can; Jiang, Hong-Wen; Hu, Xuedong; Guo, Guo-Ping
2017-01-01
Asymmetry in a three-electron double quantum dot (DQD) allows spin blockade, when spin-3/2 (quadruplet) states and spin-1/2 (doublet) states have different charge configurations. We have observed this DQD spin blockade near the (1,2)-(2,1) charge transition using a pulsed-gate technique and a charge sensor. We, then, use this spin blockade to detect Landau-Zener-Stückelberg interference and coherent oscillations between the spin quadruplet and doublet states. Such studies add to our understandings of coherence and control properties of three-spin states in a double dot, which, in turn, would benefit explorations into various qubit encoding schemes in semiconductor nanostructures.
Noncollinear Spin-Orbit Magnetic Fields in a Carbon Nanotube Double Quantum Dot
Hels, M. C.; Braunecker, B.; Grove-Rasmussen, K.; Nygârd, J.
2016-12-01
We demonstrate experimentally that noncollinear intrinsic spin-orbit magnetic fields can be realized in a curved carbon nanotube two-segment device. Each segment, analyzed in the quantum dot regime, shows near fourfold degenerate shell structure allowing for identification of the spin-orbit coupling and the angle between the two segments. Furthermore, we determine the four unique spin directions of the quantum states for specific shells and magnetic fields. This class of quantum dot systems is particularly interesting when combined with induced superconducting correlations as it may facilitate unconventional superconductivity and detection of Cooper pair entanglement. Our device comprises the necessary elements.
Bruschi, David Edward; Sabín, Carlos; Paraoanu, Gheorghe Sorin
2017-06-01
We study the properties of bisqueezed tripartite Gaussian states created by two spontaneous parametric down-conversion processes that share a common idler. We give a complete description of the quantum correlations across all partitions, as well as of the genuine multipartite entanglement, obtaining analytical expressions for most of the quantities of interest. We find that the state contains genuine tripartite entanglement, in addition to the bipartite entanglement among the modes that are directly squeezed. We also investigate the effect of homodyne detection of the photons in the common idler mode, and analyze the final reduced state of the remaining two signal modes. We find that this measurement leads to a conversion of the coherence of the two signal modes into entanglement, a phenomenon that can be regarded as a redistribution of quantum resources between the modes. The applications of these results to quantum optics and circuit quantum electrodynamics platforms are also discussed.
Quantum compact model for thin-body double-gate Schottky barrier MOSFETs
Institute of Scientific and Technical Information of China (English)
Luan Su-Zhen; Liu Hong-Xia
2008-01-01
Nanoscale Schottky barrier metal oxide semiconductor field-effect transistors (MOSFETs) are explored by using quantum mechanism effects for thin-body devices. The results suggest that for small nonnegative Schottky barrier heights, even for zero barrier height, the tunnelling current also plays a role in the total on-state current. Owing to the thin body of device, quantum confinement raises the electron energy levels in the silicon, and the tradeoff takes place between the quantum confinement energy and Schottky barrier lowering (SBL). It is concluded that the inclusion of the quantum mechanism effect in this model, which considers an infinite rectangular well with a first-order perturbation in the channel, can lead to the good agreement with numerical result for thin silicon film. The error increases with silicon thickness increasing.
Proton tunnelling in intermolecular hydrogen bonds
Energy Technology Data Exchange (ETDEWEB)
Horsewill, A.J. [Nottingham Univ. (United Kingdom); Johnson, M.R. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); Trommsdorff, H.P. [Grenoble-1 Univ., 38 (France)
1997-04-01
The wavefunctions of particles extend beyond the classically accessible regions of potential energy-surfaces (PES). A manifestation of this partial delocalization is the quantum-mechanical tunneling effect which enables a particle to escape from a metastable potential-well. Tunnelling is most important for the lightest atoms, so that the determination of its contribution to proton transfer, one of the most fundamental chemical reactions, is an important issue. QENS and NMR techniques have been employed to study the motion of protons in the hydrogen bond of benzoic-acid crystals, a system which has emerged as a particularly suitable model since proton transfer occurs in a near symmetric double-well potential. The influence of quantum tunnelling was revealed and investigated in these experiments. This work provides an experimental benchmark for theoretical descriptions of translational proton-tunnelling. (author). 7 refs.
Chuprikov, N L
2011-01-01
By probability theory the probability space to underlie the set of statistical data described by the squared modulus of a coherent superposition of microscopically distinct (sub)states (CSMDS) is non-Kolmogorovian and, thus, such data are mutually incompatible. For us this fact means that the squared modulus of a CSMDS cannot be interpreted as the probability density and quantum mechanics itself, with its current approach to CSMDSs, does not allow a correct statistical interpretation. By the example of a 1D completed scattering and double slit diffraction we develop a new quantum-mechanical approach to CSMDSs, which implies decomposition of the non-Kolmogorovian probability space associated with the squared modulus of a CSMDS into the sum of Kolmogorovian ones. We adapt to CSMDSs the presented by Khrennikov ({\\it Found. of Phys., 35, No. 10, p.1655 (2005)}) concept of real contexts (complexes of physical conditions) to determine uniquely the properties of quantum ensembles. Namely we treat the context to crea...
Desensitization and recovery of metastable intermolecular composites
Busse, James R [South Fork, CO; Dye, Robert C [Los Alamos, NM; Foley, Timothy J [Los Alamos, NM; Higa, Kelvin T [Ridgecrest, CA; Jorgensen, Betty S [Jemez Springs, NM; Sanders, Victor E [White Rock, NM; Son, Steven F [Los Alamos, NM
2010-09-07
A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.
de Bianchi, Massimiliano Sassoli
2013-01-01
The validity of the assertion that some recent double-slit interference experiments, conducted by Radin et al., would have tested the possible role of the experimenter's mind in the collapse of the quantum wave function, is questioned. It is emphasized that quantum mechanics doesn't need any psychophysical ingredient to explain the measurement processes, and therefore parapsychologists shouldn't resort to the latter to support the possibility of psychokinesis, but search for more convincing explanations.
Venâncio, Tiago; Oliveira, Lyege Magalhaes; Ellena, Javier; Boechat, Nubia; Brown, Steven P
2017-03-02
Fast magic-angle spinning (MAS) NMR is used to probe intermolecular interactions in a diethylcarbamazine salt, that is widely used as a treatment against adult worms of Wuchereria bancrofti which cause a common disease in tropical countries named filariasis. Specifically, a dihydrogen citrate salt that has improved thermal stability and solubility as compared to the free form is studied. One-dimensional (1)H, (13)C and (15)N and two-dimensional (1)H-(13)C and (14)N-(1)H heteronuclear correlation NMR experiments under moderate and fast MAS together with GIPAW (CASTEP) calculations enable the assignment of the (1)H, (13)C and (14)N/(15)N resonances. A two-dimensional (1)H-(1)H double-quantum (DQ) -single-quantum (SQ) MAS spectrum recorded with BaBa recoupling at 60kHz MAS identifies specific proton-proton proximities associated with citrate-citrate and citrate-diethylcarbamazine intermolecular interactions. Copyright © 2017 Elsevier Inc. All rights reserved.
Tuning the intermolecular proton bond in the H5O2+ `Zundel ion' scaffold
DEFF Research Database (Denmark)
Olesen, S. G.; Guasco, T. L.; Roscioli, J. R.
2011-01-01
The Zundel ion, H2O center dot H+center dot H2O, provides a versatile scaffold with which to explore the quantum structure of the intermolecular proton bond (IPB). This information is encoded in the vibrational frequencies adopted by the shared proton, nu(sp), which are observed to follow...
Electron-nuclear interaction in 13C nanotube double quantum dots
DEFF Research Database (Denmark)
Churchill, H O H; Bestwick, A J; Harlow, J W;
2009-01-01
For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource enabling storage and retrieval of quantum information. To investigate the effect of a controllable nuclear environm...
Intermolecular Interactions at high pressure
DEFF Research Database (Denmark)
Eikeland, Espen Zink
2016-01-01
In this project high-pressure single crystal X-ray diffraction has been combined with quantitative energy calculations to probe the energy landscape of three hydroquinone clathrates enclosing different guest molecules. The simplicity of the hydroquinone clathrate structures together with their st......In this project high-pressure single crystal X-ray diffraction has been combined with quantitative energy calculations to probe the energy landscape of three hydroquinone clathrates enclosing different guest molecules. The simplicity of the hydroquinone clathrate structures together...... with their structural chemistry, controlled largely by subtle interactions between the host and the enclosed guest molecules, makes them attractive to study as model systems. Quantifying the numerous superimposed interactions in these clathrates will advance our understanding of more complex supramolecular aggregates....... High-pressure crystallography is the perfect method for studying intermolecular interactions, by forcing the molecules closer together. In all three studied hydroquinone clathrates, new pressure induced phase transitions have been discovered using a mixture of pentane and isopentane as the pressure...
Hida, Kazuo
1992-03-01
The quantum disordered state (QDOS) of the spin 1/2 double layer square lattice Heisenberg antiferromagnet is studied. Using the dimer expansion from the limit of the large interlayer coupling J', the staggered susceptibility χ, the antiferromagnetic structure factor Sπ and the antiferromagnetic correlation length ξ are calculated up to the 6-th order in the intralayer coupling J. The ratio analysis shows that the QDOS becomes unstable against the Néel ordering at J'/J≃2.56. The critical exponents are not inconsistent with the universality class of the 3-dimensional classical Heisenberg model, suggesting that our QDOS corresponds to that expected in the 2-dimensional square lattice Heisenberg antiferromagnet with unphysically small spin (<0.276). The results of the projector Monte Carlo simulation also confirms the dimer expansion results.
Giant Kondo Resonance of Parallel-Coupled Double Quantum Dots Embedded in an A-B Ring
Institute of Scientific and Technical Information of China (English)
CHEN Xiong-Wen; HE Da-Jiang; SONG Ke-Hui; WU Shao-Quan
2006-01-01
We theoretically study the properties of the ground state of the parallel-coupled double quantum dots embedded in a mesoscopic ring in the Kondo regime by means of the two-impurity Anderson Hamiltonian. The Hamiltonian is solved by means of the slave-boson mean-field theory. We find that in this system, the persistent current depends sensitively on both the parity of this system and the size of the ring. In the strong coupling regime, the giant sharp current peak appears, at the same time, the parity dependence of the persistent current disappears. These imply that in the strong coupling regime, there exists giant Kondo resonance and the two dots can be coupled coherently. Thus this system might be a candidate for future device applications.
Nisticò, Giuseppe
2010-01-01
Double-slit experiment very well lends itself in describing the problem of measuring simultaneously incompatible properties. In such a context, we theoretically design an ideal experiment for spin-7/2 particles, able to produce the entanglement which makes possible the detection.
Energy Technology Data Exchange (ETDEWEB)
Lopes, E.M., E-mail: eldermantovani@yahoo.com.br [Departamento de Fisica, Quimica e Biologia, Universidade Estadual Paulista, CP 266, CEP 19060-900, Presidente Prudente, Sao Paulo (Brazil); Duarte, J.L.; Dias, I.F.L.; Laureto, E. [Departamento de Fisica, Universidade Estadual de Londrina, CP 6001, CEP 86051-970, Londrina, Parana (Brazil); Guimaraes, P.S.S.; Subtil, A.G.S. [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Minas Gerais, CP 702, CEP 30123-970, Belo Horizonte, Minas Gerais (Brazil); Quivy, A.A. [Laboratorio de Novos Materiais Semicondutores, Instituto de Fisica, Universidade de Sao Paulo, CP 66318, CEP 05315-970, Sao Paulo (Brazil)
2012-05-15
This work reports on the results of magnetophotoluminescence (MPL) measurements carried out in a sample containing two Al{sub 0.35}Ga{sub 0.65}As/GaAs, coupled double quantum wells (CDQWs), with inter-well barriers of different thicknesses, which have the heterointerfaces characterized by a distribution of bimodal roughness. The MPL measurements were performed at 4 K, with magnetic fields applied parallel to the growth direction, and varying from 0 to 12 T. The diamagnetic shift of the photoluminescence (PL) peaks is more sensitive to changes in the confinement potential, due to monolayer variations in the mini-well thickness, rather than to the exciton localization at the local potential fluctuations. As the magnetic field increases, the relative intensities of the two peaks in each PL band inverts, what is attributed to the reduction in the radiative lifetime of the delocalized excitons, which results in the radiative recombination, before the excitonic migration between the higher and lower energy regions in each CDQW occurs. The dependence of the full width at half maximum (FWHM) on magnetic field shows different behaviors for each PL peak, which are attributed to the different levels and correlation lengths of the potential fluctuations present in the regions associated with each recombination channel. - Highlights: Black-Right-Pointing-Pointer Magnetophotoluminescence results from two coupled double quantum wells are reported. Black-Right-Pointing-Pointer Each structure shows two emission channels due to bimodal heterointerface roughness. Black-Right-Pointing-Pointer Little variations on thickness have greater effect than local potential fluctuations. Black-Right-Pointing-Pointer With increasing B the excitonic migration changes between the bimodal regions. Black-Right-Pointing-Pointer The FWHM depends on level and correlation length of the potential fluctuations.
Charged excitonic complexes in GaAs/Al0.35Ga0.65As p-i-n double quantum wells
DEFF Research Database (Denmark)
Timofeev, V. B.; Larionov, A. V.; Alessi, M. Grassi
1999-01-01
Photoluminescence (PL) and PL excitation measurements (PLE) have been performed in GaAs/AlxGa1-xAs double quantum well (QW) structures under different applied electric fields. An emission due to charged excitons (trions) has been identified in the PL spectra similar to 3 meV below the heavy...
DEFF Research Database (Denmark)
Timofeev, V.B.; Larionov, A.V.; Ioselevich, A.S.;
1998-01-01
The interwell radiative recombination from biased double quantum wells (DQW) in pin GaAs/AlGaAs heterostructures is investigated at different temperatures and external electrical fields. The luminescence line of interwell recombination of spatially separated electron-hole pairs exhibits systemati...
Giant Spin-Orbit Splitting in Inverted InAs /GaSb Double Quantum Wells
Nichele, Fabrizio; Kjaergaard, Morten; Suominen, Henri J.; Skolasinski, Rafal; Wimmer, Michael; Nguyen, Binh-Minh; Kiselev, Andrey A.; Yi, Wei; Sokolich, Marko; Manfra, Michael J.; Qu, Fanming; Beukman, Arjan J. A.; Kouwenhoven, Leo P.; Marcus, Charles M.
2017-01-01
Transport measurements in inverted InAs /GaSb quantum wells reveal a giant spin-orbit splitting of the energy bands close to the hybridization gap. The splitting results from the interplay of electron-hole mixing and spin-orbit coupling, and can exceed the hybridization gap. We experimentally investigate the band splitting as a function of top gate voltage for both electronlike and holelike states. Unlike conventional, noninverted two-dimensional electron gases, the Fermi energy in InAs /GaSb can cross a single spin-resolved band, resulting in full spin-orbit polarization. In the fully polarized regime we observe exotic transport phenomena such as quantum Hall plateaus evolving in e2/h steps and a nontrivial Berry phase.
Ascertaining complementary and incompatible quantum properties by means of double-slit experiments
Energy Technology Data Exchange (ETDEWEB)
Nistico, G [Dipartimento di Matematica, Universita della Calabria, via P. Bucci 30b, 87036, Rende, Italy and Istituto Nazionale Fisica Nucleare (Italy)], E-mail: gnistico@unical.it
2008-03-28
The famous two-slits experiment is used to theoretically introduce the problem of detecting both which-slit (WS) property and another quantum property incompatible with the WS one, together with the measurement of the (complementary) position of the final impact point. General conditions for the existence of solutions are singled out, and a family of solutions is concretely found. Moreover, we theoretically design an ideal experiment which realizes this non-trivial detection.
Feasibility of Double-Click Attack on a Passive Detection Quantum Key Distribution System
Institute of Scientific and Technical Information of China (English)
ZHANG Peng; LI Chao
2011-01-01
An eavesdropper (Eve) can exploit all the imperfections of a practical quantum key distribution (QKD) system to obtain some information about the secret key,no matter whether these imperfections are from the physical layer or from the post-processing layer.We propose a possible attack on a passive detection QKD system based on the imperfection from the software layer.The analysis shows that Eve can obtain all the information about the key without being discovered.
Kang, Xiaoyan; He, Anqi; Guo, Ran; Chen, Jing; Zhai, Yanjun; Xu, Yizhuang; Noda, Isao; Wu, Jinguang
2016-11-01
The spectral behavior of a pair of 2D asynchronous spectra generated by using the double asynchronous orthogonal sample design (DAOSD) approach on a chemical system is investigated. Two solutes (P and Q) are dissolved in the solution and intermolecular interaction between P and Q is characterized. In this particular system, P occurs in two exchangeable states when it is dissolved in the solutions. Results on mathematical analysis and computer simulation demonstrated that interference unrelated to the intermolecular interaction can be completely removed. Hence the resultant 2D asynchronous spectra generated by using the DAOSD approach can reflect intermolecular interaction reliably. Moreover, properties of cross peaks in different regions of the pair of asynchronous spectra are discussed. In our previous works, cross peaks generated by using the DAOSD and relevant techniques reflect variations on peak position, bandwidth or absorptivity of the characteristic peaks of solutes caused by intermolecular interaction. However, we find that cross peak can still be produced even if intermolecular interaction do not bring about any changes on the characteristic peaks of solutes. Mathematical analysis demonstrates that cross peaks are related to the variations of chemical systems caused by intermolecular interaction at a network level.
Xifang, Chen; Wenxia, Zhang; Qianjin, Wang; Jiyang, Fan
Carbon quantum dots (CQDs) have attracted great attention in the past few years due to their low cytotoxicity, exploited various synthesis methods, unexampled abundance of raw materials on earth, and robust near-infrared to near-UV luminescence. Carbon nanoparticles have applications in biological labeling, delivery of drugs and biological molecules into cells, and light emitting diodes and lasing. CQDs generally exist as nanodiamonds or graphite quantum dots according to previous research reports. In this study, we report the first synthesis of the third-allotrope CQDs through carbonization of sucrose and study their luminescence properties. These CQDs have a body-centered cubic structure and each lattice point is composed of eight atoms which form a sub-cube (so called C8 crystal structure). High-resolution transmission electron microscopy and X-ray diffraction confirm the C8 structure of the synthesized carbon nanocrystallites with an average size of 2 nm. The C8 CQDs exhibit double-band luminescence with two peaks centered at around 432 and 520 nm. The study based on the photoluminescence, UV-Vis absorption, Fourier-transform infrared, and X-ray photoelectron spectroscopies reveals that the green emission originates from the C=O related surface defect.
Characterizing the Polymer:Fullerene Intermolecular Interactions
Sweetnam, Sean
2016-02-02
Polymer:fullerene solar cells depend heavily on the electronic coupling of the polymer and fullerene molecular species from which they are composed. The intermolecular interaction between the polymer and fullerene tends to be strong in efficient photovoltaic systems, as evidenced by efficient charge transfer processes and by large changes in the energetics of the polymer and fullerene when they are molecularly mixed. Despite the clear presence of these strong intermolecular interactions between the polymer and fullerene, there is not a consensus on the nature of these interactions. In this work, we use a combination of Raman spectroscopy, charge transfer state absorption, and density functional theory calculations to show that the intermolecular interactions do not appear to be caused by ground state charge transfer between the polymer and fullerene. We conclude that these intermolecular interactions are primarily van der Waals in nature. © 2016 American Chemical Society.
Many-body effects in intermolecular forces.
Elrod, M J; Saykally, R J
1994-11-01
The authors provide a review and literature survey of many-body effects in intermolecular forces. Topics include experimental methods, theoretical methods, many-body effects in atomic systems, and many-body effects in aqueous and nonaqueous molecular systems.
Energy Technology Data Exchange (ETDEWEB)
Ivanov, Sergei D., E-mail: sergei.ivanov@unirostock.de; Grant, Ian M.; Marx, Dominik [Lehrstuhl für Theoretische Chemie, Ruhr–Universität Bochum, 44780 Bochum (Germany)
2015-09-28
With the goal of computing quantum free energy landscapes of reactive (bio)chemical systems in multi-dimensional space, we combine the metadynamics technique for sampling potential energy surfaces with the ab initio path integral approach to treating nuclear quantum motion. This unified method is applied to the double proton transfer process in the formic acid dimer (FAD), in order to study the nuclear quantum effects at finite temperatures without imposing a one-dimensional reaction coordinate or reducing the dimensionality. Importantly, the ab initio path integral metadynamics technique allows one to treat the hydrogen bonds and concomitant proton transfers in FAD strictly independently and thus provides direct access to the much discussed issue of whether the double proton transfer proceeds via a stepwise or concerted mechanism. The quantum free energy landscape we compute for this H-bonded molecular complex reveals that the two protons move in a concerted fashion from initial to product state, yet world-line analysis of the quantum correlations demonstrates that the protons are as quantum-uncorrelated at the transition state as they are when close to the equilibrium structure.
Generation of vector beams using a double-wedge depolarizer: Non-quantum entanglement
Samlan, C. T.; Viswanathan, Nirmal K.
2016-07-01
Propagation of horizontally polarized Gaussian beam through a double-wedge depolarizer generates vector beams with spatially varying state of polarization. Jones calculus is used to show that such beams are maximally nonseparable on the basis of even (Gaussian)-odd (Hermite-Gaussian) mode parity and horizontal-vertical polarization state. The maximum nonseparability in the two degrees of freedom of the vector beam at the double wedge depolarizer output is verified experimentally using a modified Sagnac interferometer and linear analyser projected interferograms to measure the concurrence 0.94±0.002 and violation of Clauser-Horne-Shimony-Holt form of Bell-like inequality 2.704±0.024. The investigation is carried out in the context of the use of vector beams for metrological applications.
Zhang, Yu-Feng; Huang, Rong-Yi; Wang, Jun-Wei; Geng, Tong-Mou; Zhao, Shun-Ping; Wu, Gen-Hua
2014-09-01
In this Letter, excess molar volumes, refractive index deviations, Raman spectra and quantum-chemical calculations have been used to explore the underlying intermolecular interactions in the binary mixture containing cyclopentanone (CPN) and methanol. The experimental data reveal that the 1:1 (Ia) and 1:2 (Ib) cross-associations between CPN and methanol are formed in the studied binary mixture. This result has been further corroborated via theoretical calculations. In addition, the observed 1747 and 1732 cm-1 bands can be assigned to the Cdbnd O stretching vibrations of the intermolecular cross-associations Ia and Ib, respectively, in distinct contradiction with the previous explanations.
Iiyama, Taku; Hagi, Kousuke; Urushibara, Takafumi; Ozeki, Sumio
2009-01-01
The intermolecular structure of C(2)H(5)OH molecules confined in slit-shaped graphitic micropore of activated carbon fiber was investigated by in situ X-ray diffraction (XRD) measurement and reverse Monte Carlo (RMC) analysis. The pseudo-3-dimensional intermolecular structure Of C(2)H(5)OH adsorbed in the micropores was determined by applying the RMC analysis to XRD data, assuming a simple slit-shaped space composed of double graphene sheets. The results were consistent with conventional Mont...
Ultraslow optical solitons in tunnel-coupled double semiconductor quantum well
Institute of Scientific and Technical Information of China (English)
Chen Ai-Xi; Xu Yan-Qiu; Deng Li; Zhou Su-Yun
2009-01-01
This paper investigates the nonlinear evolution of the pulse probe field in an asymmetric coupled-quantum well driven coherently by a pulse probe field and two controlled fields.This study shows that,by choosing appropriate physical parameters,self-modulation can precisely balance group velocity dispersion in the investigated system,leading to the formation of ultraslow optical solitons of the probe field.The proposed scheme may lead to the development of the controlled technique of optical buffers and optical delay lines.
Continuous-Variable Entanglement in Tunnel-Coupled Double Quantum Wells
Institute of Scientific and Technical Information of China (English)
L(U) Xin-You; LIU Ji-Bing; HAO Xiang-Ying; HUANG Pei; YANG Xiao-Xue
2009-01-01
This paper investigates the generation and evolution of continuous-variable entanglement in an asymmetric coupled-quantum well (CQW) system. Our numerical results show that this CQW system can be regarded as a source of macroscopic entangled light over a wide range of initial states of the cavity field. This investigation can be used for achieving the macroscopic entangled light in the CQW solid-state medium, which is much more practical than that in an atomic medium because of its flexible design and the controllable interference strength.
Perspectives for quantum state engineering via high non-linearity in a double-EIT regime
Paternostro, M; Ham, B S
2003-01-01
We analyse the possibilities for quantum state engineering offered by a model for Kerr-type non-linearity enhanced by electromagnetically induced transparency (EIT), which was recently proposed by Petrosyan and Kurizki [{\\sl Phys. Rev. A} {\\bf 65}, 33833 (2002)]. We go beyond the semiclassical treatment and derive a quantum version of the model with both a full Hamiltonian approach and an analysis in terms of dressed states. The preparation of an entangled coherent state via a cross-phase modulation effect is demonstrated. We briefly show that the violation of locality for such an entangled coherent state is robust against low detection efficiency. Finally, we investigate the possibility of a bi-chromatic photon blockade realized via the interaction of a low density beam of atoms with a bi-modal electromagnetic cavity which is externally driven. We show the effectiveness of the blockade effect even when more than a single atom is inside the cavity. The possibility to control two different cavity modes allows ...
Chen, Zhangjin; Liang, Yaqiu; Lin, C D
2010-06-25
Based on the full quantal recollision model and field-free electron impact ionization theory, we calculate the correlated momentum spectra of the two outgoing electrons in strong field nonsequential double ionization (NSDI) of helium to compare with recent experiments. By analyzing the relative strength of binary versus recoil collisions exhibited in the photoelectron spectra, we confirm that the observed fingerlike structure in the experiment is a consequence of the Coulomb interaction between the two emitted electrons. Our result supports the recollision mechanism of strong field NSDI at the most fundamental level.
Dispersive properties of tunnelling-induced transparency in an asymmetric double quantum well
Institute of Scientific and Technical Information of China (English)
苏雪梅; 卓仲畅; 王立军; 高锦岳
2002-01-01
We have investigated the dispersive properties of tunnelling-induced transparency in asymmetric double quantumwell structures where two excited states are coupled by resonant tunnelling through a thin barrier in a three-levelsystem of electronic subbands. The intersubband transitions exhibit high dispersion at zero absorption, which leads tothe slow light velocity in this medium as compared with that in vacuum (c＝3× 108). The group velocity in a specificGaAs/AlGaAs sample is calculated to be vg＝c/4.30. This structure can be used to compensate for the dispersion andenergy loss in fibre optical communications.
Tiutiunnyk, A.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. M.; Restrepo, R. L.; Ungan, F.; Martínez-Orozco, J. C.; Kasapoglu, E.; Duque, C. A.
2017-02-01
In this work we shall present a study of inelastic light scattering involving inter-subband electron transitions in coupled GaAs-(Ga,Al)As quantum wells. Calculations include the electron related Raman differential cross section and Raman gain. The effects of an external nonresonant intense laser field are used in order to tune these output properties. The confined electron states will be described by means of a diagonalization procedure within the effective mass and parabolic band approximations. It is shown that the application of the intense laser field can produce values of the intersubband electron Raman gain above 400 cm-1. The system proposed here is an alternative choice for the development of AlxGa1-xAs semiconductor laser diodes that can be tuned via an external nonresonant intense laser field.
Conditions for observing emergent SU(4) symmetry in a double quantum dot
Nishikawa, Yunori; Curtin, Oliver J.; Hewson, Alex C.; Crow, Daniel J. G.; Bauer, Johannes
2016-06-01
We analyze conditions for the observation of a low-energy SU(4) fixed point in capacitively coupled quantum dots. One problem, due to dots with different couplings to their baths, has been considered by L. Tosi, P. Roura-Bas, and A. A. Aligia, J. Phys.: Condens. Matter 27, 335601 (2015), 10.1088/0953-8984/27/33/335601. They showed how symmetry can be effectively restored via the adjustment of individual gates voltages, but they make the assumption of infinite on-dot and interdot interaction strengths. A related problem is the difference in the magnitudes between the on-dot and interdot strengths for capacitively coupled quantum dots. Here we examine both factors, based on a two-site Anderson model, using the numerical renormalization group to calculate the local spectral densities on the dots and the renormalized parameters that specify the low-energy fixed point. Our results support the conclusions of Tosi et al. that low-energy SU(4) symmetry can be restored, but asymptotically achieved only if the interdot interaction U12 is greater than or of the order of the bandwidth of the coupled conduction bath D , which might be difficult to achieve experimentally. By comparing the SU(4) Kondo results for a total dot occupation ntot=1 and 2, we conclude that the temperature dependence of the conductance is largely determined by the constraints of the Friedel sum rule rather than the SU(4) symmetry and suggest that an initial increase of the conductance with temperature is a distinguishing characteristic feature of an ntot=1 universal SU(4) fixed point.
Senokos, E.; Reguero, V.; Palma, J.; Vilatela, J. J.; Marcilla, Rebeca
2016-02-01
In this work we present a combined electrochemical and mechanical study of mesoporous electrodes based on CNT fibres in the context of electric double layer capacitors. We show that through control of the synthetic and assembly processes of the fibres, it is possible to obtain an active material that combines a surface area of 250 m2 g-1, high electrical conductivity (3.5 × 105 S m-1) and mechanical properties in the high-performance range including toughness (35 J g-1) comparable to that of aramid fibre (e.g. Kevlar). These properties are a consequence of the predominant orientation of the CNTs, observed by wide- and small-angle X-ray diffraction, and to the exceptionally long CNT length on the millimetre scale. Cyclic voltammetry measurements in a three-electrode configuration and using 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR14TFSI) ionic liquid electrolyte, show that the CNT fibres have a large quantum capacitance, evidenced by the near linear dependence of geometric capacitance (and conductivity) on potential bias. This reflects the low dimensionality of the CNT building blocks, which were purposely synthesised to have 1-5 layers and a high degree of graphitization. From the charge-discharge measurements of supercapacitor devices with symmetric CNT fibre electrodes we obtain power and energy densities as high as 58 kW kg-1 and 14 Wh kg-1, respectively. These record-high values for CNT fibre-based supercapacitors, are a consequence of the low equivalent series resistance due to the high conductivity of the fibres, the large contribution from quantum capacitance, and the wide stability window of the ionic liquid (3.5 V). Cycle life experiments demonstrate stable capacitance and energy retention over 10 000 cycles of charge-discharge at 3.5 V.In this work we present a combined electrochemical and mechanical study of mesoporous electrodes based on CNT fibres in the context of electric double layer capacitors. We show that through
Al-Khalili, Jim
2003-01-01
In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.
Kondo, Kenji
2016-01-01
Many researchers have reported on spin filters using linear Rashba spin-orbit interactions (SOI). However, spin filters using square and cubic Rashba SOIs have not yet been reported. We consider that this is because the Aharonov-Casher (AC) phases acquired under square and cubic Rashba SOIs are ambiguous. In this study, we try to derive the AC phases acquired under square and cubic Rashba SOIs from the viewpoint of non-Abelian SU(2) gauge theory. These AC phases can be derived successfully from the non-Abelian SU(2) gauge theory without the completing square methods. Using the results, we investigate the spin filtering in a double quantum dot (QD) Aharonov-Bohm (AB) ring under linear, square, and cubic Rashba SOIs. This AB ring consists of elongated QDs and quasi-one-dimensional quantum nanowires under an external magnetic field. The spin transport is investigated from the left nanowire to the right nanowire in the above structure within the tight-binding approximation. In particular, we focus on the difference of spin filtering among linear, square, and cubic Rashba SOIs. The calculation is performed for the spin polarization by changing the penetrating magnetic flux for the AB ring subject to linear, square, and cubic Rashba SOIs. It is found that perfect spin filtering is achieved for all of the Rashba SOIs. This result indicates that this AB ring under general Rashba SOIs can be a promising device for spin current generation. Moreover, the AB rings under general Rashba SOIs behave in totally different ways in response to penetrating magnetic flux, which is attributed to linear, square, and cubic behaviors in the in-plane momentum. This result enables us to make a clear distinction between linear, square, and cubic Rashba SOIs according to the peak position of the perfect spin filtering.
Yakunin, M. V.; Krishtopenko, S. S.; Podgornykh, S. M.; Popov, M. R.; Neverov, V. N.; Mikhailov, N. N.; Dvoretsky, S. A.
2016-09-01
The quantum Hall effect (QHE) in a HgTe/CdHgTe double quantum well (DQW) with a tunneling-transparent barrier and the energy spectrum resembling the band structure of bilayer graphene has been investigated. An experimental manifestation of a tunnel gap between the states of light carriers seen as a magnetoresistance (MR) peak in the in-plane magnetic field has been discovered. An unusual structure of the QHE has been observed in a sample with hole conductivity: there is a pronounced peak on a plateau with the number i = 2 and the slopes of this anomalous peak correspond to two peaks of the longitudinal MR. On the other hand, a stable 2-1 plateau-plateau transition has been observed in much higher fields with the position of this transition corresponding to a considerably higher hole density than follows from the pattern of the QHE in weak fields. The anomalous peak is interpreted as a reentrant QHE between the 2-1-2 states. The position of the anomalous peak is immune to IR illumination and the tilting angle of the magnetic field, although these factors strongly affect its amplitude. According to comparison with the calculated structure of magnetic levels, the anomalous peak is attributed to crossing of electron-like and hole-like levels in the valence band. The difference between the hole densities found in weak field and from the 2-1 transition in strong fields is attributed to the effects of redistribution of holes between the localized states in sideband maxima of the valence subband and the ones delocalized in the overlapping levels of light holes.
Energy Technology Data Exchange (ETDEWEB)
Atanasov, Atanas Todorov, E-mail: atanastod@abv.bg [Department of Physics and Biophysics, Faculty of Medicine, Trakia University, 11 Armeiska Str., 6000 Stara Zagora (Bulgaria)
2014-10-06
The scaling of physical and biological characteristics of the living organisms is a basic method for searching of new biophysical laws. In series of previous studies the author showed that in Poikilotherms, Mammals and Aves, the volume to surface ratio V×S{sup −1} (m) of organisms is proportional to their generation time T{sub gt}(s) via growth rate v (m s{sup −1}): V×S{sup −1} = v{sub gr}×T{sup r}. The power and the correlation coefficients are near to 1.0. Aim of this study is: i) to prove with experimental data the validity of the above equation for Unicellular organisms and ii) to show that perhaps, the cells are quantum-mechanical systems. The data for body mass M (kg), density ρ (kg/m{sup 3}), minimum and maximum doubling time T{sub dt} (s) for 50 unicellular organisms are assembled from scientific sources, and the computer program ‘Statistics’ is used for calculations. In result i) the analytical relationship from type: V×S{sup −1} = 4.46⋅10{sup −11}×T{sub dt} was found, where v{sub gr} = 4.46×10{sup −11} m/s and ii) it is shown that the products between cell mass M, cell length expressed by V/S ratio and growth rate v{sub gr} satisfied the Heisenberg uncertainty principle i.e. the inequalities V/S×M×v{sub gr}>h/2π and T{sub dt}×M×v{sub gr}{sup 2}>h/2π are valid, where h= 6.626×10{sup −34} J⋅s is the Planck constant. This rise the question: do cells appear quantum-mechanical systems?.
Son, Ji-Su; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi
2014-01-01
The characteristics of nonpolar a-plane (11\\bar{2}0) GaN (a-GaN) grown using single and double nanopillar SiO2 masks were investigated. The two nanopillar SiO2 masks were directly fabricated on an r-plane sapphire substrate and a-GaN by the epitaxial lateral overgrowth (ELOG) technique. Through the use of the single and double nanopillar SiO2 masks, the crystalline quality and optical properties of a-GaN were markedly improved because of the nanoscale ELOG effect and a number of voids in the single and double nanopillar SiO2 mask areas in comparison with the planar sample. The submicron pit densities of the planar, single, and double nanopillar mask samples were ˜2 × 109, ˜7 × 108, and ˜4 × 108 cm-2, respectively. The internal quantum efficiency (IQE) values at room temperature of three-period InGaN/GaN multiple quantum wells (MQWs) grown using the planar, single, and double nanopillar masks were 45, 60, and 68% at a carrier concentration of 1.0 × 1018 cm-3, respectively.
Towards optimizing two-qubit operations in three-electron double quantum dots
Frees, Adam; Gamble, John King; Mehl, Sebastian; Friesen, Mark; Coppersmith, S. N.
The successful implementation of single-qubit gates in the quantum dot hybrid qubit motivates our interest in developing a high fidelity two-qubit gate protocol. Recently, extensive work has been done to characterize the theoretical limitations and advantages in performing two-qubit operations at an operation point located in the charge transition region. Additionally, there is evidence to support that single-qubit gate fidelities improve while operating in the so-called ``far-detuned'' region, away from the charge transition. Here we explore the possibility of performing two-qubit gates in this region, considering the challenges and the benefits that may present themselves while implementing such an operational paradigm. This work was supported in part by ARO (W911NF-12-0607) (W911NF-12-R-0012), NSF (PHY-1104660), ONR (N00014-15-1-0029). The authors gratefully acknowledge support from the Sandia National Laboratories Truman Fellowship Program, which is funded by the Laboratory Directed Research and Development (LDRD) Program. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.
Quantum parameter space and double scaling limits in N=1 super Yang-Mills theory
Ferrari, Frank
2003-04-01
We study the physics of N=1 super Yang-Mills theory with the gauge group U(N) and one adjoint Higgs field, by using the recently derived exact effective superpotentials. Interesting phenomena occur for some special values of the Higgs potential couplings. We find critical points with massless glueballs and/or massless monopoles, confinement without a mass gap, and tensionless domain walls. We describe the transitions between regimes with different patterns of gauge symmetry breaking, or, in the matrix model language, between solutions with a different number of cuts. The standard large N expansion is singular near the critical points, with domain wall tensions scaling as a fractional power of N. We argue that the critical points are four-dimensional analogues of the Kazakov critical points that are commonly found in low dimensional matrix integrals. We define a double scaling limit that yields the exact tension of BPS two-branes in the resulting N=1, four-dimensional noncritical string theory. D-brane states can be deformed continuously into closed string solitonic states, and vice versa, along paths that go over regions where the string coupling is strong.
Quantum parameter space and double scaling limits in N=1 super Yang-Mills theory
Ferrari, F
2003-01-01
We study the physics of N=1 super Yang-Mills theory with gauge group U(Nc) and one adjoint Higgs field, by using the recently derived exact effective superpotentials. Interesting phenomena occur for some special values of the Higgs potential couplings. We find critical points with massless glueballs and/or massless monopoles, confinement without a mass gap, and tensionless domain walls. We describe the transitions between regimes with different patterns of gauge symmetry breaking, or, in the matrix model language, between solutions with a different number of cuts. The standard large Nc expansion is singular near the critical points, with domain walls tensions scaling as a fractional power of Nc. We argue that the critical points are four dimensional analogues of the Kazakov critical points that are commonly found in low dimensional matrix integrals. We define a double scaling limit that yields the exact tension of BPS two-branes in the resulting N=1, four dimensional non-critical string theory. D-brane states...
Polynomial identities for ternary intermolecular recombination
Bremner, Murray R
2010-01-01
The operation of binary intermolecular recombination, originating in the theory of DNA computing, permits a natural generalization to n-ary operations which perform simultaneous recombination of n molecules. In the case n = 3, we use computer algebra to determine the polynomial identities of degree <= 9 satisfied by this trilinear nonassociative operation. Our approach requires computing a basis for the nullspace of a large integer matrix, and for this we compare two methods: (i) the row canonical form, and (ii) the Hermite normal form with lattice basis reduction. In the conclusion, we formulate some conjectures for the general case of n-ary intermolecular recombination.
Energy Technology Data Exchange (ETDEWEB)
Lopez, S.Y. [Grupo de Educacion en Ciencias Experimentales y Matematicas-GECEM, Facultad de Educacion, Universidad de Antioquia, AA 1226 Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque@fisica.udea.edu.c [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)
2009-12-15
The photoluminescence energy transitions in GaAs-Ga{sub 1-x}Al{sub x}As coupled double quantum wells are presented by considering the simultaneous effects of applied electric and magnetic fields and hydrostatic pressure. Calculations have been made in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electric field is taken to be oriented along the growth direction of the heterostructure whereas for the magnetic field both in-plane and in-growth directions have been considered. The results show that the hydrostatic pressure and the applied electric field are two useful tools to tune the direct and indirect exciton transitions in such heterostructures. Our results are in good agreement with previous experimental findings in double quantum wells under applied electric field and hydrostatic pressure.
Donor states in a semimagnetic Cd1 -xinMnxin Te /Cd1 -xoutMnxout Te Double Quantum Well
Kalpana, Panneer Selvam; Nithiananthi, Perumal; Jayakumar, Kalyanasundaram
2017-02-01
The theoretical investigation has been carried out on the binding energy of donor associated with the electrons confined in a Cd1 -xinMnxin Te /Cd1 -xoutMnxout Te Double Quantum Well (DQW) as a function of central barrier width for various well dimensions and impurity locations in the barrier and the well. The magnetic field can act as a tool to continuously change the interwell coupling inside this DQW systems and its effect on donor binding has also been studied. Moreover, the polaronic corrections, which is due to the strong exchange interaction between the magnetic moment of Mn2+ ion and the spin of the confined carrier, to the binding energy of the hydrogenic donor impurity has also been estimated with and without the application of magnetic field. The binding energy of the donor impurity is determined by solving the Schrodinger equation variationally in the effective mass approximation and the effect due to Bound Magnetic Polaron (BMP) is included using mean field theory with the modified Brillouin function. The results are reported and discussed.
Wu, Menghao; Wang, Zhijun; Liu, Junwei; Li, Wenbin; Fu, Huahua; Sun, Lei; Liu, Xin; Pan, Minghu; Weng, Hongming; Dincă, Mircea; Fu, Liang; Li, Ju
2017-03-01
Bandstructure with Dirac cones gives rise to massless Dirac fermions with rich physics, and here we predict rich cone properties in M 3C12S12 and M 3C12O12, where M = Zn, Cd, Hg, Be, or Mg based on recently synthesized Ni3C12S12—class 2D metal-organic frameworks (MOFs). For M 3C12S12, their band structures exhibit double Dirac cones with different Fermi velocities that are n (electron) and p (hole) type, respectively, which are switchable by few-percent strain. The crossing of two cones are symmetry-protected to be non-hybridizing, leading to two independent channels at the same k-point akin to spin-channels in spintronics, rendering ‘conetronics’ device possible. For M 3C12O12, together with conjugated metal-tricatecholate polymers M 3(HHTP)2, the spin-polarized slow Dirac cone center is pinned precisely at the Fermi level, making the systems conducting in only one spin/cone channel. Quantum anomalous Hall effect can arise in MOFs with non-negligible spin-orbit coupling like Cu3C12O12. Compounds of M 3C12S12 and M 3C12O12 with different M, can be used to build spin/cone-selecting heterostructure devices tunable by strain or electrostatic gating, suggesting their potential applications in spintroincs/conetronics.
Transport properties of double-gate SiO{sub 2}-Si-SiO{sub 2} quantum well
Energy Technology Data Exchange (ETDEWEB)
Prunnila, Mika; Ahopelto, Jouni [VTT Information Technology, Microelectronics, P.O. Box 1208, 02044 VTT (Finland); Sakaki, Hiroyuki [University of Tokyo, Institute of Industrial Science, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8503 (Japan)
2005-05-01
We report on fabrication and low temperature transport properties of double-gate SiO{sub 2}-Si-SiO{sub 2} quantum well with a 16.5 nm thick Si layer. The device is fabricated on a silicon-on-insulator substrate utilizing wafer bonding, which enables us to use heavily doped back gate. Transport properties of the device are characterized by low field Hall and high field magnetotransport measurements at 4.2 K and at 0.38 K, respectively. Top (back) Si-SiO{sub 2} interface peak mobility of 1.9 m{sup 2}/Vs (1.0 m{sup 2}/Vs) is measured at 4.2 K. When both gates have a (large) positive bias the Hall carrier density is observed to fall below the value of the expected total carrier density, which is interpreted to arise from the occupancy of the second sub-band in the Si well. This is confirmed by the high field magnetotransport measurements. In quantizing magnetic fields the longitudinal resistivity minima show Landau level filling factor behavior which is typical for weakly coupled bi-layers. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Tang, Yanqun; Wang, Ruirui; Yang, Ye; Yan, Dongpeng; Xiang, Xu
2016-08-03
The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is ∼1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.
Institute of Scientific and Technical Information of China (English)
CHEN Xiong-Wen; SHI Zhen-Gang; CHEN Bao-Ju; SONG Ke-Hui
2007-01-01
We analyse the transport properties of a coupled double quantum dot (DQD) device with one of the dots (QD1) coupled to metallic leads and the other (QD2) embedded in an Aharonov-Bhom (A-B) ring by means of the slave-boson mean-Geld theory. It is found that in this system, the Kondo resonance and the Fano interference exist simultaneously, the enhancing Kondo effect and the increasing hopping of the QD2-Ring destroy the localized electron state in the QD2 for the QD1-leads, and accordingly, the Fano interference between the DQD-leads and the QD1-leads are suppressed. Under some conditions, the Fano interference can be quenched fully and the single Kondo resonance of the QD1-leads comes into being. Moreover, when the magnetic flux of the A-B ring is zero, the influence of the parity of the A-B ring on the transport properties is very weak, but this inSuence becomes more obvious with non-zero magnetic flux. Thus this model may be a candidate for future device applications.
双量子阱中的子带光吸收%Intersubband Optical Absorption in Double Quantum Wells
Institute of Scientific and Technical Information of China (English)
邓永晴; 郭康贤; 于凤梅; 俞友宾; 王瑞强
2005-01-01
Recently, much attention has been focus on the investigation of the electroabsorption in the GaAs/AlGaAs quantum wells (QW's) because of its possibility of designing new types of electro-optic modulators. Much optical properties of the single QW's with different potential has been and being investigated experimently and theoriticaly with different methods. In these few years, the double quantum wells (DQWs) became the focus of the research. In this paper, by using the density matrix formalism and iterated method, the first-and the third-order intersubband optical absorption of double quantum well with infinit boundary was investigated theoretically. Thereafter, a typical GaAs/AlGaAs DQWs is presented to get the results. The results show that the peak absorption varies with the width of the intermediate potential barrier. And it also shows that the absorption decrease as the incident optical intensity increasing.%由于微制造技术的不断发展,如液相外延(LPE),气相外延(VPE),金属有机化学气相沉积(MOCVD)以及分子束外延技术(MBE)等先进的材料生长技术方法也日趋完善,从而使得各种低维半导体量子器件(如半导体、超晶格、量子阱、量子线和量子点等)制造日趋成熟.由于这些低维半导体量子器件具有很强的非线性光效应,而且随着材料、外形、尺寸等的不同,非线性光效应也有很大的差别,更由于其可能存在的广泛的应用前景,所以近年来,一直是人们研究的重点.近来,由于人们相信,利用GaAs/AlGaAs量子阱有可能制造出一些新型的光学仪器,如光开关、光限幅器、光调制器等,所以,对不同势形的GaAs/AlGaAs量子阱的非线性光学特性一直吸引着人们进行理论和实验的研究.而在最近几年,对双量子阱的研究也成为了人们的研究重点.通过密度矩阵和迭代的方法,得到双量子阱中的第一、第三阶子带光吸收表达式,我们将用一个典型的GaAs/AlGaAs双
Directory of Open Access Journals (Sweden)
SUBHA SUBRAMANIAM
2013-01-01
Full Text Available In this paper modeling framework for single gate conventional planar MOSFET and double gate (DG MOSFETS are reviewed. MOS Modeling can be done by either analytical modeling or compact modeling. Single gate MOSFET technology has been the choice of mainstream digital circuits for VLSI as well as for other high frequency application in the low GHZ range. The major single gate MOS modeling methods are reviewed and compared. First generation to fifth generation MOS models like BSIM & PSP are compared. The use of multiple gates has emerged as a new technology to replace the conventional planar MOSFET when itsfeature size is scaled to the sub 22nm regime. Double Gate devices seem to be attractive alternatives as they can effectively reduce the short channel effects and yield higher current drive. DGFETS are classified as Symmetric Double Gate FETs (SDGFET and Asymmetric Double Gate FETs (ADGFET. This paper covers the fundamentals of SDGFETs and ADGFETs. Drain current models for single gate MOSFETs, SDGFETs and ADGFETs are reviewed. In the Double gate MOS era the dominating quantum mechanical effects which has to be considered in two dimensional modeling are also discussed. The comparisons of drain current models for Symmetric and Asymmetric Double gate MOSFETs are done and shown with the results like limitations of the models. A brief summary of the review work is provided. The result shows a greater demand in the field of Asymmetric Double gate modeling which can be extended for circuits like SRAM and RF amplifier design. Thepremier quantum mechanical effects which should be included in model development for below 22nm devices are listed.
González-Fernández, J. V.; Herrera-Jasso, R.; Ulloa-Castillo, N. A.; Ortega-Gallegos, J.; Castro-García, R.; Lastras-Martínez, L. F.; Lastras-Martínez, A.; Balderas-Navarro, R. E.; Mozume, T.; Gozu, S.
2016-12-01
We report on photoreflectance anisotropy (PRA) spectroscopy of InGaAs/AlAs/AlAsSb coupled double quantum wells (CDQWs) with extremely thin coupling AlAs barriers grown by molecular beam epitaxy (MBE), with no intentional doping. By probing the in-plane interfacial optical anisotropies (OAs), it is shown that PRA spectroscopy has the ability to detect and distinguish semiconductor layers with quantum dimensions, as the anisotropic photoreflectance (PR) signal stems entirely from buried quantum wells (QWs). In order to account for the experimental PRA spectra, a theoretical model at k = 0, based on a linear electro-optic effect through a piezoelectric shear strain, has been employed to quantify the internal electric fields across the QWs. The dimensionalities of the PR lineshapes were tested by using reciprocal (Fourier) space analysis. Such a complementary test is used in order to correctly employ the PRA model developed here.
Energy Technology Data Exchange (ETDEWEB)
Rojas-Briseño, J.G.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia)
2013-09-01
In this work we are reporting the energy level spectrum for a quantum system consisting of an n-type double δ-doped quantum well with a Schottky barrier potential in a Gallium Arsenide matrix. The calculated states are taken as the basis for the evaluation of the linear and third-order nonlinear contributions to the optical absorption coefficient and to the relative refractive index change, making particular use of the asymmetry of the potential profile. These optical properties are then reported as a function of the Schottky barrier height (SBH) and the separation distance between the δ-doped quantum wells. Also, the effects of the application of hydrostatic pressure are studied. The results show that the amplitudes of the resonant peaks are of the same order of magnitude of those obtained in the case of single δ-doped field effect transistors; but tailoring the asymmetry of the confining potential profile allows the control the resonant peak positions.
Intramolecular versus intermolecular hydrogen bonding in solution
Vliegenthart, J.F.G.; Kroon, Jan; Kroon-Batenburg, L.M.J.; Leeflang, B.R.
1994-01-01
The balance between intra- and intermolecular hydrogen bonding is studied for a solution of methyl beta-cellobioside in water and dimethylsulfoxide by 1H NMR and molecular dynamics simulations. In water O(3) predominantly interacts with water molecules, whereas in dimethylsulfoxide it is
Energy Technology Data Exchange (ETDEWEB)
Daqiq, Reza; Ghobadi, Nader
2016-07-15
We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching. - Highlights: • The quantum size effects are studied in double barrier magnetic tunnel junctions. • Spin torque (ST) components oscillate for increasing of middle spacer thicknesses. • Due to the resonant tunneling in the quantum well, oscillations have appeared. • By replacement a metal spacer with a semiconductor (ZnO) ST has increased. • The ST components vs. bias show gradually decreasing unlike spin valves or MTJs.
Catalytic intermolecular alkene oxyamination with nitrenes.
Dequirez, Geoffroy; Ciesielski, Jennifer; Retailleau, Pascal; Dauban, Philippe
2014-07-14
The Rh(II)-catalyzed intermolecular addition of nitrenes to aromatic and aliphatic alkenes provides vicinal amino alcohols with yields of up to 95 % and complete regioselectivity. This 1,2-oxyamination reaction involves the formation of an aziridine intermediate that undergoes in situ ring opening. The latter is induced by the Rh-bound nitrene that behaves as a Lewis acid. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Double slit quantum imaging experiment based on correlation of photon pairs%基于关联光子对的双缝量子成像实验
Institute of Scientific and Technical Information of China (English)
杨青; 夏慧枝; 陈凯
2015-01-01
双缝量子成像实验利用参量下转换过程产生的光子之间的关联性，扫描双缝量子成像。通过采集光子符合计数，绘制扫描位置和光子符合计数关联图，在一维方向重现双缝。根据实验采集数据和绘图结果计算双缝缝间距。%Double slit quantum imaging experiment used the correlation of the photon pairs ,w hich generated by PDC ,to scan the double slit quantum imaging .By collecting the photon coincidence number ,drawing the correlation picture of scanning position and photon coincidence number , the double slit in one‐dimension was reconstructed .The distance of the two slit was calculated in the light of the experiment result .
Topic, Wendy C.; Jäger, Wolfgang
2005-08-01
Rotational spectra of the weakly bound He-HCCCN and He-DCCCN van der Waals complexes were observed using a pulsed-nozzle Fourier-transform microwave spectrometer in the 7-26-GHz frequency region. Nuclear quadrupole hyperfine structures due to the N14 and D nuclei (both with nuclear-spin quantum number I =1) were resolved and assigned. Both strong a and weaker b-type transitions were observed and the assigned transitions were used to fit the parameters of a distortable asymmetric rotor model. The dimers are floppy, near T-shaped complexes. Three intermolecular potential-energy surfaces were calculated using the coupled-cluster method with single and double excitations and noniterative inclusion of triple excitations. Bound-state rotational energy levels supported by these surfaces were determined. The quality of the potential-energy surfaces was assessed by comparing the experimental and calculated transition frequencies and also the corresponding spectroscopic parameters. Simple scaling of the surfaces improved both the transition frequencies and spectroscopic constants. Five other recently reported surfaces [O. Akin-Ojo, R. Bukowski, and K. Szalewicz, J. Chem. Phys. 119, 8379 (2003)], calculated using a variety of methods, and their agreement with spectroscopic properties of He-HCCCN are discussed.
Institute of Scientific and Technical Information of China (English)
Hong Xue-Kun; Yang Xi-Feng; Feng Jin-Fu; Liu Yu-Shen
2013-01-01
We propose a Rashba three-terminal double-quantum-dot device to generate a spin-polarized current and manipulate the electron spin in each quantum dot by utilizing the temperature gradient instead of the electric bias voltage.This device possesses a nonresonant tunneling channel and two resonant tunneling channels.The Keldysh nonequilibrium Green's function techniques are employed to determinate the spin-polarized current flowing from the electrodes and the spin accumulation in each quantum dot.We find that their signs and magnitudes are well controllable by the gate voltage or the temperature gradient.This result is attributed to the change in the slope of the transmission probability at the Fermi levels in the low-temperature region.Importantly,an obviously pure spin current can be injected into or extracted from one of the three electrodes by properly choosing the temperature gradient and the gate voltages.Therefore,the device can be used as an ideal thermal generator to produce a pure spin current and manipulate the electron spin in the quantum dot.
Shah, Khurshed A.; Bhat, Bashir Mohi Ud Din
2016-10-01
In this paper we report the effect of external magnetic field and core radius on the excited quantum state energies of an electron confined in the core of a double walled carbon nanotube. The goal is accomplished by using Wentzel-Kramers-Brillioun (WKB) approximation method within the effective mass approximation and confinement potential. All numerical analysis were carried out in a strong confinement regime. The results show that the electron energy increases with the increase in external magnetic field at a given core radii. The electron energy is also found to increase as the core radius of the CNT decreases and for core radius a > 5 nm the energy becomes almost zero. The effect of magnetic field on the excited state energies of the confined electron is more evident for smaller core radius acarbon nanotube quantum dot devices [1].
Abedi, Kambiz
2011-12-01
In this paper, the strain effect on saturation optical intensity in electroabsorption modulators (EAMs) based on asymmetric intra-step-barrier coupled double strained quantum well (AICD-SQWs) active region is theoretically investigated and compared with intra-step quantum well (IQW) structure. For this purpose, the thermionic emission and tunneling escape processes are taken into account and the escape times of photogenerated carriers are calculated. Then, the electroabsorption coefficient is calculated for different well strains for TE input light polarization. Finally, the saturation optical intensity of electroabsorption modulators with AICD-SQW structures in comparison with IQW structure is evaluated. Numerical results show that the tensile strain of well has the most significant effect on the saturation optical intensity of electroabsorption modulators with AICD-SQW structures due to reduction in escape times.
Institute of Scientific and Technical Information of China (English)
Xue Hui-Jie; Lü Tian-Quan; Zhang Hong-Chen; Yin Hai-Tao; Cui Lian; He Ze-Long
2012-01-01
The thermoelectric and the thermospin transport properties,including electrical conductivity,Seebeck coefficient,thermal conductivity,and thermoelectric figure of merit,of a parallel coupled double-quantum-dot Aharonov-Bohm interferometer are investigated by means of the Green function technique.The periodic Anderson model is used to describe the quantum dot system,the Rashba spin-orbit interaction and the Zeeman splitting under a magnetic field are considered.The theoretical results show the constructive contribution of the Rashba effect and the influence of the magnetic field on the thermospin effects.We also show theoretically that material with a high figure of merit can be obtained by tuning the Zeeman splitting energy only.
Probst, B.; Domínguez, F.; Schroer, A.; Yeyati, A. Levy; Recher, P.
2016-10-01
We study the critical Josephson current flowing through a double quantum dot weakly coupled to two superconducting leads. We use analytical as well as numerical methods to investigate this setup in the limit of small and large bandwidth leads in all possible charging states, where we account for on-site interactions exactly. Our results provide clear signatures of nonlocal spin-entangled pairs, which support interpretations of recent experiments [R. S. Deacon, A. Oiwa, J. Sailer, S. Baba, Y. Kanai, K. Shibata, K. Hirakawa, and S. Tarucha, Nat. Commun. 6, 7446 (2015), 10.1038/ncomms8446]. In addition, we find that the ground state with one electron on each quantum dot can undergo a tunable singlet-triplet phase transition in the regime where the superconducting gap in the leads is not too large, which gives rise to an additional new signature of nonlocal Cooper-pair transport.
Organic narrowband near-infrared photodetectors based on intermolecular charge-transfer absorption.
Siegmund, Bernhard; Mischok, Andreas; Benduhn, Johannes; Zeika, Olaf; Ullbrich, Sascha; Nehm, Frederik; Böhm, Matthias; Spoltore, Donato; Fröb, Hartmut; Körner, Christian; Leo, Karl; Vandewal, Koen
2017-06-05
Blending organic electron donors and acceptors yields intermolecular charge-transfer states with additional optical transitions below their optical gaps. In organic photovoltaic devices, such states play a crucial role and limit the operating voltage. Due to its extremely weak nature, direct intermolecular charge-transfer absorption often remains undetected and unused for photocurrent generation. Here, we use an optical microcavity to increase the typically negligible external quantum efficiency in the spectral region of charge-transfer absorption by more than 40 times, yielding values over 20%. We demonstrate narrowband detection with spectral widths down to 36 nm and resonance wavelengths between 810 and 1,550 nm, far below the optical gap of both donor and acceptor. The broad spectral tunability via a simple variation of the cavity thickness makes this innovative, flexible and potentially visibly transparent device principle highly suitable for integrated low-cost spectroscopic near-infrared photodetection.
Gall', L N; Gall', N R
2009-01-01
A novel concept of intermolecular energy transfer and reception of the ultralow action in living systems is proposed. The concept is based on the methods of nonlinear mathematical physics used in description of energy movement along molecular chains and on quantum mechanical ideas concerning signal formation in anisotropic media. A concept of a molecular cell as an indivisible structural unit and a constituent of a biological (chemical) system has been put forward and substantiated, which manifests collective features of the unity of molecules, physical fields, and energetically strained bound water media in processes of energy transfer and reception. Both intermolecular energy transfer and amplification of the ultralow action has been shown to be the components of a unified energy process in a living system, and the physical basis of both processes is the unity of molecules and water-field media in a molecular cell.
Interactions in dendronized polymers: intramolecular dominates intermolecular.
Córdova-Mateo, Esther; Bertran, Oscar; Zhang, Baozhong; Vlassopoulos, Dimitris; Pasquino, Rossana; Schlüter, A Dieter; Kröger, Martin; Alemán, Carlos
2014-02-21
In an attempt to relate atomistic information to the rheological response of a large dendritic object, interand intramolecular hydrogen bonds and p,p-interactions have been characterized in a dendronized polymer (DP) that consists of a polymethylmethacrylate backbone with tree-like branches of generation four (PG4) and contains both amide and aromatic groups. Extensive atomistic molecular dynamics simulations have been carried out on (i) an isolated PG4 chain and (ii) ten dimers formed by two PG4 chains associated with different degrees of interpenetration. Results indicate that the amount of nitrogen atoms involved in hydrogen bonding is ~11% while ~15% of aromatic groups participate in p,pinteractions. Furthermore, in both cases intramolecular interactions clearly dominate over intermolecular ones, while exhibiting markedly different behaviors. Specifically, the amount of intramolecular hydrogen bonds increases when the interpenetration of the two chains decreases, whereas intramolecular p,pinteractions remain practically insensitive to the amount of interpenetration. In contrast, the strength of the corresponding two types of intermolecular interactions decreases with interpenetration. Although the influence of complexation on the density and cross-sectional radius is relatively small, interpenetration affects significantly the molecular length of the DP. These results support the idea of treating DPs as long colloidal molecules.
Teymoori, Gholamhasan; Pahari, Bholanath; Edén, Mattias
2015-12-01
We provide an experimental, numerical, and high-order average Hamiltonian evaluation of an open-ended series of homonuclear dipolar recoupling sequences, SR2 2p 1 with p = 1, 2, 3, … . While operating at a very low radio-frequency (rf) power, corresponding to a nutation frequency of 1/2 of the magic-angle spinning (MAS) rate (ωnut =ωr / 2), these recursively generated double-quantum (2Q) dipolar recoupling schemes offer a progressively improved compensation to resonance offsets and rf inhomogeneity for increasing pulse-sequence order p. The excellent recoupling robustness to these experimental obstacles, as well as to CSA, is demonstrated for 2Q filtering (2QF) experiments and for driving magnetization transfers in 2D NMR correlation spectroscopy, where the sequences may provide either double or zero quantum dipolar Hamiltonians during mixing. Experimental and numerical demonstrations, which mostly target conditions of "ultra-fast" MAS (≳50 kHz) and high magnetic fields, are provided for recoupling of 13C across a wide range of isotropic and anisotropic chemical shifts, as well as dipolar coupling constants, encompassing [2,3-13C2 ]alanine, [1,3-13C2 ]alanine, diammonium [1,4-13C2 ]fumarate, and [U-13 C]tyrosine. When compared at equal power levels, a superior performance is observed for the SR2p 1 sequences with p ⩾ 3 relative to existing and well-established 2Q recoupling techniques. At ultra-fast MAS, proton decoupling is redundant during the homonuclear dipolar recoupling of dilute spins in organic solids, which renders the family of SR2p 1 schemes the first efficient 2Q recoupling option for general applications, such as 2Q-1Q correlation NMR and high-order multiple-quantum excitation, under truly low-power rf conditions.
An Intermolecular Vibration Model for Lattice Ice
Directory of Open Access Journals (Sweden)
Quinn M. Brewster
2010-06-01
Full Text Available Lattice ice with tetrahedral arrangement is studied using a modified Einstein’s model that incorporates the hindered translational and rotational vibration bands into a harmonic oscillation system. The fundamental frequencies for hindered translational and rotational vibrations are assigned based on the intermolecular vibration bands as well as thermodynamic properties from existing experimental data. Analytical forms for thermodynamic properties are available for the modified model, with three hindered translational bands at (65, 229, 229 cm-1 and three effective hindered rotational bands at 560 cm-1. The derived results are good for temperatures higher than 30 K. To improve the model below 30 K, Lorentzian broadening correction is added. This simple model helps unveil the physical picture of ice lattice vibration behavior.
Persistent photoeffects in p-i-n GaAs/AlGaAs heterostructures with double quantum wells
DEFF Research Database (Denmark)
Dorozhkin, S.I.; Timofeev, V.B.; Hvam, Jørn Märcher
2001-01-01
Abrupt changes in the capacitance between the p and n regions were observed in a planar p-i-n GaAs/AlGaAs heterostructure with two tunneling-coupled quantum wells exposed to laser irradiation (lambda = 633 nm). These changes can be caused by variations in both temperature (in the vicinity of T...
量子理论新方法研究光的双缝衍射%Photon Double-slit Diffraction with Quantum Theory Approach
Institute of Scientific and Technical Information of China (English)
严立云; 李宏; 刘晓静; 王婧; 张斯淇; 吴坤朋; 李春红; 吴向尧; 郭义庆
2013-01-01
用量子理论新方法研究光的双缝衍射实验现象,首先用光的量子理论计算光在缝中双缝衍射的波函数,再由基尔霍夫定律计算光的衍射波函数,由衍射强度正比于衍射波函数模方,从而得到光双缝衍射强度的解析式,把量子理论计算结果和经典电磁理论计算结果以及与实验数据三者进行比较,发现量子理论结果与实验数据符合更好,而经典电磁理论计算结果与实验有一定偏差.从而说明量子理论更能精确解释光的衍射现象.该方法还可进一步研究光的单缝、多缝以及光栅衍射的实验现象.%In this paper, the light double-slit diffraction with quantum theory approach is studied. Firstly, the light wave function in slits is calculated, and the diffraction wave function is obtained with Kirchhoff's law. The diffraction intensity is proportional to the diffraction wave function da party. Futhermore, the intensity formula of light double-slit diffraction is obtained; by comparing the quantum theory calculation results and classical electromagnetic theory calculation results and the experimental date, it is found that the calculate result of quantum theory is in accordance with the experment data, but the classical electromagnetic theory calculation result with the experiment date has certain deviation. So, the quantum theory can explain the light diffraction more precisely. The proposed method can also further study the light of the single slit, many slits and grating diffraction experiment phenomena.
Harbach, Philipp H P; Schneider, Matthias; Faraji, Shirin; Dreuw, Andreas
2013-03-21
Intermolecular coulombic decay (ICD) is an efficient mechanism of low-energy electron generation in condensed phases and is discussed as their potential source in living cells, tissues, and materials. The first example of ICD as an operating mechanism in real biological systems, that is, in the DNA repair enzymes photolyases, is presented. Photolyase function involves light-induced electron detachment from a reduced flavin adenine dinucleotide (FADH(-)), followed by its transfer to the DNA-lesion triggering repair of covalently bound nucleobase dimers. Modern quantum chemical methods are employed to demonstrate that the transferred electron is efficiently generated via a resonant ICD process between the antenna pigment and the FADH(-) cofactors.
The effect of intermolecular hydrogen bonding on the fluorescence of a bimetallic platinum complex.
Zhao, Guang-Jiu; Northrop, Brian H; Han, Ke-Li; Stang, Peter J
2010-09-02
The bimetallic platinum complexes are known as unique building blocks and arewidely utilized in the coordination-driven self-assembly of functionalized supramolecular metallacycles. Hence, photophysical study of the bimetallic platinum complexes will be very helpful for the understanding on the optical properties and further applications of coordination-driven self-assembled supramolecular metallacycles. Herein, we report steady-state and time-resolved spectroscopic experiments as well as quantum chemistry calculations to investigate the significant intermolecular hydrogen bonding effects on the intramolecular charge transfer (ICT) fluorescence of a bimetallic platinum compound 4,4'-bis(trans-Pt(PEt(3))(2)OTf)benzophenone 3 in solution. We demonstrated that the fluorescent state of compound 3 can be assigned as a metal-to-ligand charge transfer (MLCT) state. Moreover, it was observed that the formation of intermolecular hydrogen bonds can effectively lengthen the fluorescence lifetime of 3 in alcoholic solvents compared with that in hexane solvent. At the same time, the electronically excited states of 3 in solution are definitely changed by intermolecular hydrogen bonding interactions. As a consequence, we propose a new fluorescence modulation mechanism by hydrogen bonding to explain different fluorescence emissions of 3 in hydrogen-bonding solvents and nonhydrogen-bonding solvents.
Daqiq, Reza; Ghobadi, Nader
2016-07-01
We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching.
Teymoori, Gholamhasan; Pahari, Bholanath; Stevensson, Baltzar; Edén, Mattias
2012-09-01
We report novel symmetry-based radio-frequency (rf) pulse sequences for efficient excitation of double-quantum (2Q) coherences under very fast (>60 kHz) magic-angle spinning (MAS) conditions. The recursively generated pulse-scheme series, R22p1R22p-1(p=1,2,3,…), offers broadband 13C-13C recoupling in organic solids at a very low rf power. No proton decoupling is required. A high-order average Hamiltonian theory analysis reveals a progressively enhanced resonance-offset compensation for increasing p, as verified both by numerical simulations and 2Q filtration NMR experiments on 13C2-glycine, [2,3-13C2]alanine, and [U-13C]tyrosine at 14.1 T and 66 kHz MAS, where the pulse schemes with p⩾3 compare favorably to current state-of-the-art recoupling options.
Influence of Width of left Well on Intersubband Transitions in AlxGa1-x N/GaN Double Quantum Wells
Institute of Scientific and Technical Information of China (English)
LEI Shuang-Ying; SHEN Bo; ZHANG Guo-Yi
2008-01-01
Influence of width of lett well in Alx Ga1-x N/GaN double quantum wells (DQWs) on absorption coefficients and wavelengths of the intersubband transitions (ISBTs) is investigated by solving the SchrSdinger and Poisson equations self-consistently. When the width of lett well is 1.79nm, three-energy-level DQ, Ws are realized. The ISBT between the first odd and second odd order subbands (the lodd-2odd ISBT) has a comparable absorption coeffcient with the 1odd-2even ISBT. Their wavelengths are located at 1.3 and 1.55μm, respectively. When the width of lett well is 1.48nm, a four-energy-level DQWs is realized. The calculated results have a possible application to ultrafast two-colour optoeleetronic devices operating within the optical communication wavelength range.
Bejan, Doina
2016-10-01
The effects of the potential shape asymmetry on the nonlinear optical absorption and optical rectification in GaAs double quantum dots under intense non-resonant laser field and static electric field were investigated comparatively using the effective mass approximation and the compact density-matrix formalism under steady state conditions. The obtained results show that: (i) for both systems, the optical spectra are redshifted with the increase of the laser intensity only in the presence of the electric field, exceptions appearing at the highest considered laser intensity for both systems and at low laser field intensity for the asymmetric system; (ii) the augment of the static field intensity blueshifts the optical spectra of both systems; (iii) the spectra of the asymmetric system are displaced toward higher energies and show a shoulder-like feature at a given electric field value; (iv) the optical rectification spectra are more intense for the symmetric system.
Energy Technology Data Exchange (ETDEWEB)
Miranda, Guillermo L. [Fisica Teorica y Aplicada, Escuela de Ingenieria de Antioquia, A.A. 7516 Medellin (Colombia); Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia); Mora-Ramos, Miguel E., E-mail: memora@uaem.mx [Fisica Teorica y Aplicada, Escuela de Ingenieria de Antioquia, A.A. 7516 Medellin (Colombia); Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209 Cuernavaca, Morelos (Mexico); Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia); Duque, Carlos A. [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)
2013-01-15
In this work the variations of the exciton-related optical absorption and the change of the refractive index in a GaAs-(Ga,Al)As double quantum well as functions of the geometric parameters of the heterostructure are investigated. The variational method is applied within the framework of the parabolic band and effective mass approximations, in order to obtain the 1s-like exciton energy spectrum. The outcome for the related optical coefficients shows a quenched and redshifted light absorption as a result of the increment in the inner barrier and right-hand well widths, with the possibility of an enhancement of the excitonic contribution to the relative change in the refractive index.
Energy Technology Data Exchange (ETDEWEB)
Fan, Yao; Liu, Li; Sun, Donglei; Lan, Hanyue [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China); Fu, Haiyan, E-mail: fuhaiyan@mail.scuec.edu.cn [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China); Yang, Tianming, E-mail: tmyang@mail.scuec.edu.cn [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China); She, Yuanbin, E-mail: sheyb@zjut.edu.cn [State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Ni, Chuang [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China)
2016-04-15
As a popular detection model, the fluorescence “turn-off” sensor based on quantum dots (QDs) has already been successfully employed in the detections of many materials, especially in the researches on the interactions between pesticides. However, the previous studies are mainly focused on simple single track or the comparison based on similar concentration of drugs. In this work, a new detection method based on the fluorescence “turn-off” model with water-soluble ZnCdSe and CdSe QDs simultaneously as the fluorescent probes is established to detect various pesticides. The fluorescence of the two QDs can be quenched by different pesticides with varying degrees, which leads to the differences in positions and intensities of two peaks. By combining with chemometrics methods, all the pesticides can be qualitative and quantitative respectively even in real samples with the limit of detection was 2 × 10{sup −8} mol L{sup −1} and a recognition rate of 100%. This work is, to the best of our knowledge, the first report on the detection of pesticides based on the fluorescence quenching phenomenon of double quantum dots combined with chemometrics methods. What's more, the excellent selectivity of the system has been verified in different mediums such as mixed ion disruption, waste water, tea and water extraction liquid drugs. - Highlights: • A new model based on double QDs is established for pesticide residues detection. • The fluorescent data array sensor is coupled with chmometrics methods. • The sensor can be highly sensitive and selective detection in actual samples.
Energy Technology Data Exchange (ETDEWEB)
Zhang, L. [State Key Laboratory for Mesoscopic Physics, and School of Physics, Peking University, Beijing 100871 (China) and Department of Mechanism and Electron, Panyu Polytechnic, Panyu 511483 (China)]. E-mail: zhangli-gz@263.net; Chi Yuemeng [State Key Laboratory for Mesoscopic Physics, and School of Physics, Peking University, Beijing 100871 (China); Shi, J.-J. [State Key Laboratory for Mesoscopic Physics, and School of Physics, Peking University, Beijing 100871 (China)
2007-06-25
Based on the density matrix method and the iterative treatment, the second-harmonic generation (SHG) susceptibility of a wurtzite nitride coupling quantum well (CQW) with strong built-in electric fields have been theoretically investigated. The effect of the band non-parabolicity effect has been taken into account. A typical wurtzite GaN/In{sub x}Ga{sub 1-x}N CQW are chosen to perform numerical calculations. The localized properties of the electronic ground state and the low-excited states in the system are analyzed in detail. The calculated SHG coefficients reach the order of magnitude of 10{sup -7}m/V, which is two-order larger than the corresponding values in wurtzite single quantum wells. Moreover, it is confirmed that the SHG coefficients are not monotonic functions of the well width, barrier width and the doped concentration of the CQW systems, but have complicated dependent relations on them. The reasons resulting in these characteristics can be attributed to the intense competition between the strong built-in electric field effect and the quantum size effect for the electronic confined situation in the wurtzite CQWs. The calculated results also show that a strong SHG effect can be realized in the nitride CQW by choosing a group of optimized structural parameters and doped fraction.
Human DNA ligase III bridges two DNA ends to promote specific intermolecular DNA end joining.
Kukshal, Vandna; Kim, In-Kwon; Hura, Gregory L; Tomkinson, Alan E; Tainer, John A; Ellenberger, Tom
2015-08-18
Mammalian DNA ligase III (LigIII) functions in both nuclear and mitochondrial DNA metabolism. In the nucleus, LigIII has functional redundancy with DNA ligase I whereas LigIII is the only mitochondrial DNA ligase and is essential for the survival of cells dependent upon oxidative respiration. The unique LigIII zinc finger (ZnF) domain is not required for catalytic activity but senses DNA strand breaks and stimulates intermolecular ligation of two DNAs by an unknown mechanism. Consistent with this activity, LigIII acts in an alternative pathway of DNA double strand break repair that buttresses canonical non-homologous end joining (NHEJ) and is manifest in NHEJ-defective cancer cells, but how LigIII acts in joining intermolecular DNA ends versus nick ligation is unclear. To investigate how LigIII efficiently joins two DNAs, we developed a real-time, fluorescence-based assay of DNA bridging suitable for high-throughput screening. On a nicked duplex DNA substrate, the results reveal binding competition between the ZnF and the oligonucleotide/oligosaccharide-binding domain, one of three domains constituting the LigIII catalytic core. In contrast, these domains collaborate and are essential for formation of a DNA-bridging intermediate by adenylated LigIII that positions a pair of blunt-ended duplex DNAs for efficient and specific intermolecular ligation.
Human DNA ligase III bridges two DNA ends to promote specific intermolecular DNA end joining
Kukshal, Vandna; Kim, In-Kwon; Hura, Gregory L.; Tomkinson, Alan E.; Tainer, John A.; Ellenberger, Tom
2015-01-01
Mammalian DNA ligase III (LigIII) functions in both nuclear and mitochondrial DNA metabolism. In the nucleus, LigIII has functional redundancy with DNA ligase I whereas LigIII is the only mitochondrial DNA ligase and is essential for the survival of cells dependent upon oxidative respiration. The unique LigIII zinc finger (ZnF) domain is not required for catalytic activity but senses DNA strand breaks and stimulates intermolecular ligation of two DNAs by an unknown mechanism. Consistent with this activity, LigIII acts in an alternative pathway of DNA double strand break repair that buttresses canonical non-homologous end joining (NHEJ) and is manifest in NHEJ-defective cancer cells, but how LigIII acts in joining intermolecular DNA ends versus nick ligation is unclear. To investigate how LigIII efficiently joins two DNAs, we developed a real-time, fluorescence-based assay of DNA bridging suitable for high-throughput screening. On a nicked duplex DNA substrate, the results reveal binding competition between the ZnF and the oligonucleotide/oligosaccharide-binding domain, one of three domains constituting the LigIII catalytic core. In contrast, these domains collaborate and are essential for formation of a DNA-bridging intermediate by adenylated LigIII that positions a pair of blunt-ended duplex DNAs for efficient and specific intermolecular ligation. PMID:26130724
Gobet, Mallory; Rondeau-Mouro, Corinne; Buchin, Solange; Le Quéré, Jean-Luc; Guichard, Elisabeth; Foucat, Loïc; Moreau, Céline
2010-04-01
The feasibility of solid-state magic angle spinning (MAS) (31)P nuclear magnetic resonance (NMR) spectroscopy and (23)Na NMR spectroscopy to investigate both phosphates and Na(+) ions distribution in semi-hard cheeses in a non-destructive way was studied. Two semi-hard cheeses of known composition were made with two different salt contents. (31)P Single-pulse excitation and cross-polarization MAS experiments allowed, for the first time, the identification and quantification of soluble and insoluble phosphates in the cheeses. The presence of a relatively 'mobile' fraction of colloidal phosphates was evidenced. The detection by (23)Na single-quantum NMR experiments of all the sodium ions in the cheeses was validated. The presence of a fraction of 'bound' sodium ions was evidenced by (23)Na double-quantum filtered NMR experiments. We demonstrated that NMR is a suitable tool to investigate both phosphates and Na(+) ions distributions in cheeses. The impact of the sodium content on the various phosphorus forms distribution was discussed and results demonstrated that NMR would be an important tool for the cheese industry for the processes controls.
Chen, Chong; Ling, Lanyu; Li, Fumin
2017-12-01
In this paper, to improve the power conversion efficiencies (PCEs) of quantum dot-sensitized solar cells (QDSSCs) based on CdS-sensitized TiO2 nanotube (TNT) electrodes, two methods are employed on the basis of our previous work. First, by replacing the traditional single-sided working electrodes, double-sided transparent TNT/ITO (DTTO) electrodes are prepared to increase the loading amount of quantum dots (QDs) on the working electrodes. Second, to increase the light absorption of the CdS-sensitized DTTO electrodes and improve the efficiency of charge separation in CdS-sensitized QDSSCs, copper indium disulfide (CuInS2) is selected to cosensitize the DTTO electrodes with CdS, which has a complementary property of light absorption with CdS. The PCEs of QDSSCs based on these prepared QD-sensitized DTTO electrodes are measured. Our experimental results show that compared to those based on the CdS/DTTO electrodes without CuInS2, the PCEs of the QDSSCs based on CdS/CuInS2-sensitized DTTO electrode are significantly improved, which is mainly attributed to the increased light absorption and reduced charge recombination. Under simulated one-sun illumination, the best PCE of 1.42% is achieved for the QDSSCs based on CdS(10)/CuInS2/DTTO electrode, which is much higher than that (0.56%) of the QDSSCs based on CdS(10)/DTTO electrode.
Fan, Yao; Liu, Li; Sun, Donglei; Lan, Hanyue; Fu, Haiyan; Yang, Tianming; She, Yuanbin; Ni, Chuang
2016-04-15
As a popular detection model, the fluorescence "turn-off" sensor based on quantum dots (QDs) has already been successfully employed in the detections of many materials, especially in the researches on the interactions between pesticides. However, the previous studies are mainly focused on simple single track or the comparison based on similar concentration of drugs. In this work, a new detection method based on the fluorescence "turn-off" model with water-soluble ZnCdSe and CdSe QDs simultaneously as the fluorescent probes is established to detect various pesticides. The fluorescence of the two QDs can be quenched by different pesticides with varying degrees, which leads to the differences in positions and intensities of two peaks. By combining with chemometrics methods, all the pesticides can be qualitative and quantitative respectively even in real samples with the limit of detection was 2 × 10(-8) mol L(-1) and a recognition rate of 100%. This work is, to the best of our knowledge, the first report on the detection of pesticides based on the fluorescence quenching phenomenon of double quantum dots combined with chemometrics methods. What's more, the excellent selectivity of the system has been verified in different mediums such as mixed ion disruption, waste water, tea and water extraction liquid drugs.
Energy Technology Data Exchange (ETDEWEB)
Khazanova, S. V., E-mail: khazanova@phys.unn.ru; Degtyarev, V. E.; Malekhonova, N. V.; Pavlov, D. A. [Nizhni Novgorod State University (Russian Federation); Baidus, N. V. [Nizhni Novgorod State University, Physical Technical Research Institute (Russian Federation)
2015-01-15
A comprehensive analysis of double tunnel-coupled InGaAs/GaAs quantum well heterostructures is carried out. The real composition profiles of the structures are obtained by high-resolution transmission electron microscopy and energy-dispersive spectrometry. The resultant profiles are compared with the profile obtained by computer simulation. By solving the Schrödinger equation in combination with the Poisson equation, the energy states for quantum-confined heterostructures with initially specified and real composition profiles are calculated. The influence of a number of factors, such as the well width, barrier thickness, and the background doping level on the properties of the heterostructure is thoroughly analyzed. In this manner, the optical characteristics and their dependence on the growth technology and geometric parameters of the structures are studied. Such an approach makes it possible to refine the real geometric parameters of wells and barriers and to correct the parameters of the structure and growth technology in order to improve the optical characteristics.
Intermolecular Vibrations of Hydrophobic Amino Acids
Williams, Michael Roy Casselman
Hydrophobic amino acids interact with their chemical environment through a combination of electrostatic, hydrogen bonding, dipole, induced dipole, and dispersion forces. These interactions all have their own characteristic energy scale and distance dependence. The low-frequency (0.1-5 THz, 5-150 cm-1) vibrational modes of amino acids in the solid state are a direct indicator of the interactions between the molecules, which include interactions between an amino acid functional group and its surroundings. This information is central to understanding the dynamics and morphology of proteins. The alpha-carbon is a chiral center for all of the hydrophobic amino acids, meaning that they exist in two forms, traditionally referred to as L- and D-enantiomers. This nomenclature indicates which direction the molecule rotates plane-polarized visible light (levorotory and dextrorotory). Chiral a-amino acids in proteins are exclusively the L-variety In the solid state, the crystal lattice of the pure L-enantiomer is the mirror image of the D-enantiomer crystal lattice. These solids are energetically identical. Enantiomers also have identical spectroscopic properties except when the measurement is polarization sensitive. A mixture of equal amounts D- and L-amino acid enantiomers can crystallize into a racemic (DL-) structure that is different from that of the pure enantiomers. Whether a solution of both enantiomers will crystallize into a racemic form or spontaneously resolve into a mixture of separate D- and L-crystals largely depends on the interactions between molecules available in the various possible configurations. This is an active area of research. Low-frequency vibrations with intermolecular character are very sensitive to changes in lattice geometry, and consequently the vibrational spectra of racemic crystals are usually quite distinct from the spectra of the crystals of the corresponding pure enantiomers in the far-infrared (far-IR). THz time-domain spectroscopy (THz
Energy Technology Data Exchange (ETDEWEB)
Wang, Jiyin; Huang, Shaoyun, E-mail: hqxu@pku.edu.cn, E-mail: syhuang@pku.edu.cn; Lei, Zijin [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Pan, Dong; Zhao, Jianhua [State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Xu, H. Q., E-mail: hqxu@pku.edu.cn, E-mail: syhuang@pku.edu.cn [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Division of Solid State Physics, Lund University, Box 118, S-22100 Lund (Sweden)
2016-08-01
We demonstrate direct measurements of the spin-orbit interaction and Landé g factors in a semiconductor nanowire double quantum dot. The device is made from a single-crystal pure-phase InAs nanowire on top of an array of finger gates on a Si/SiO{sub 2} substrate and the measurements are performed in the Pauli spin-blockade regime. It is found that the double quantum dot exhibits a large singlet-triplet energy splitting of Δ{sub ST} ∼ 2.3 meV, a strong spin-orbit interaction of Δ{sub SO} ∼ 140 μeV, and a large and strongly level-dependent Landé g factor of ∼12.5. These results imply that single-crystal pure-phase InAs nanowires are desired semiconductor nanostructures for applications in quantum information technologies.
Spin–orbit-coupled BEC in a double-well potential: Quantum energy spectrum and flat band
Energy Technology Data Exchange (ETDEWEB)
Wang, Wen-Yuan [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); National Laboratory of Science and Technology on Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Cao, Hui, E-mail: hcao.physics@gmail.com [National Laboratory of Science and Technology on Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Liu, Jie [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); National Laboratory of Science and Technology on Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Center for Applied Physics and Technology, Peking University, Beijing 100084 (China); Fu, Li-Bin, E-mail: lbfu@iapcm.ac.cn [National Laboratory of Science and Technology on Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Center for Applied Physics and Technology, Peking University, Beijing 100084 (China)
2015-09-04
Spin–orbit-coupled Bose–Einstein condensates (BECs) provide a powerful platform for studies on physical problems in various fields. Here we study the energy spectrum of a tunable spin–orbit-coupled BEC in a double-well potential with adjustable Raman laser intensity. We find in the single-particle spectrum there is a highly degenerate flat band in the ground state of the BEC, which remains stable against changes of the Raman strength. Many-body interactions between atoms remove this high degeneracy. Analytical results for particular cases are obtained by using the perturbation theory, which are in good agreement with the numerical results. - Highlights: • Energy spectrum of a tunable SOC BEC in a double-well potential is obtained. • Single-particle spectrum shows a highly degenerate flat band in the ground state. • Weak interactions between atoms remove this high degeneracy. • Analytical results are obtained by perturbation theory.
Intermolecular interaction studies of glyphosate with water
Manon, Priti; Juglan, K. C.; Kaur, Kirandeep; Sethi, Nidhi; Kaur, J. P.
2017-07-01
The density (ρ), viscosity (η) and ultrasonic velocity (U) of glyphosate with water have been measured on different ultrasonic frequency ranges from 1MHz, 2MHz, 3MHz & 5MHz by varying concentrations (0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, & 0.40%) at 30°C. The specific gravity bottle, Ostwald's viscometer and quartz crystal interferometer were used to determine density (ρ), viscosity (η) and ultrasonic velocity (U). These three factors contribute in evaluating the other parameters as acoustic impedance (Z), adiabatic compressibility (β), relaxation time (τ), intermolecular free length (Lf), free volume (Vf), ultrasonic attenuation (α/f2), Rao's constant (R), Wada's constant (W) and relative strength (R). Solute-solvent interaction is confirmed by ultrasonic velocity and viscosity values, which increases with increase in concentration indicates stronger association between solute and solvent molecules. With rise in ultrasonic frequency the interaction between the solute and solvent particles decreases. The linear variations in Rao's constant and Wada's constant suggest the absence of complex formation.
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Lu Liangliang; Xie Wenfang, E-mail: lll516946435@126.com [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China)
2011-08-01
The linear and nonlinear optical properties such as optical absorption and refractive index change associated with intersubband transitions in a two-electron quantum dot (QD) in the presence of an external electric field have been investigated theoretically by using the perturbation method. The exchange force, which is a strictly quantum mechanical phenomenon, has also been considered. Numerical results on typical GaAs/AlGaAs materials show that an increase of the electric field decreases the oscillator strengths, the peak positions of absorption coefficients as well as the refractive index changes. Additionally, an increase of the confinement frequency (dot size) increases (decreases) the absorption coefficients but does not significantly affect the refractive index changes. It is also observed that the intensity of the illumination and the relaxation time have drastic effects on nonlinear optical properties. Finally, we note that the optical absorption coefficients and refractive index changes of two electrons are about five times higher than that of a one-electron QD.
Parani, Sundararajan; Bupesh, Giridharan; Manikandan, Elayaperumal; Pandian, Kannaiyan; Oluwafemi, Oluwatobi Samuel
2016-11-01
Water-soluble, mercaptosuccinic acid (MSA)-capped CdTe/CdS/ZnS core/double shell quantum dots (QDs) were prepared by successive growth of CdS and ZnS shells on the as-synthesized CdTe/CdSthin core/shell quantum dots. The formation of core/double shell structured QDs was investigated by ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) spectroscopy, PL decay studies, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The core/double shell QDs exhibited good photoluminescence quantum yield (PLQY) which is 70% higher than that of the parent core/shell QDs, and they are stable for months. The average particle size of the core/double shell QDs was ˜3 nm as calculated from the transmission electron microscope (TEM) images. The cytotoxicity of the QDs was evaluated on a variety of cancer cells such as HeLa, MCF-7, A549, and normal Vero cells by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) cell viability assay. The results showed that core/double shell QDs were less toxic to the cells when compared to the parent core/shell QDs. MCF-7 cells showed proliferation on incubation with QDs, and this is attributed to the metalloestrogenic activity of cadmium ions released from QDs. The core/double shell CdTe/CdS/ZnS (CSS) QDs were conjugated with transferrin and successfully employed for the biolabeling and fluorescent imaging of HeLa cells. These core/double shell QDs are highly promising fluorescent probe for cancer cell labeling and imaging applications.
Liu, A.-Peng; Cheng, Liu-Yong; Guo, Qi; Zhang, Shou; Zhao, Ming-Xia
2017-01-01
We propose deterministic schemes for controlled-NOT (CNOT), Toffoli, and Fredkin gates between flying photon qubits and the collective spin wave (magnon) of an atomic ensemble inside double-sided optical microcavities. All the gates can be accomplished with 100% success probability in principle and no additional qubit is required. Atomic ensemble is employed so that light-matter coupling is remarkably improved by collective enhancement. We qualified the performance of the gates and the results show that they can be faithfully constituted with current experimental techniques. PMID:28272548
Matsumoto, Hisato; Nishimura, Yoshinobu; Arai, Tatsuo
2016-08-04
The photodimerization reaction of anthracene derivatives was performed by capitalizing on intermolecular hydrogen bonds. Anthracene derivatives that can control the dimerization reaction depending on the substitution site were designed by using two anthryl moieties and one urea group, referred to as N,N'-dianthracen-n-ylurea, nDAU (n = 1, 2 and 9), which are symmetrically substituted by 1-anthryl, 2-anthryl and 9-anthryl groups, respectively. We investigated the excimer emission and photodimerization reaction of these anthracene-urea derivatives using absorption, emission, and (1)H NMR spectroscopy along with fluorescence decay measurements. All derivatives showed a concentration dependence of their fluorescence spectra and multiple fluorescence lifetime components even at 10(-6) M. Significantly, 9DAU resulted in an intermolecular photodimerization reaction. These differences in photoreactivity of nDAU may depend on variations in the overlap of the intermolecularly associated anthracene rings of nDAU by hydrogen bonding between intermolecular urea moieties. Furthermore, the dimerization quantum yield of 9DAU was reduced by the addition of tetrabutylammonium acetate (TBAAc). Consequently, we revealed that the substitution site and the addition of TBAAc affected the dimerization reaction of anthracene-urea derivatives.
Energy Technology Data Exchange (ETDEWEB)
Rodríguez-Magdaleno, K.A.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calz. Solidaridad Esq. Paseo a La Bufa S/N. C.P. 98060 Zacatecas (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca, Morelos (Mexico); Física Teórica y Aplicada, Escuela de Ingeniería de Antioquia, AA 7516 Medellín (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)
2014-03-15
In this work, the conduction band electron states and the associated intersubband-related linear and nonlinear optical absorption coefficient and relative refractive index change are calculated for an asymmetric double n-type δ-doped quantum well in a GaAs-matrix. The effects of an external applied static electric field are included. Values of the two-dimensional impurities density (N{sub 2d}) of each single δ-doped quantum well are taken to vary within the range of 1.0×10{sup 12} to 7.0×10{sup 12} cm{sup −2}, consistent with the experimental data growth regime. The optical responses are reported as a function of the δ-doped impurities density and the applied electric field. It is shown that single electron states and the related optical quantities are significantly affected by the structural asymmetry of the double δ-doped quantum well system. In addition, a brief comparison with the free-carrier-related optical response is presented. -- Highlights: • Nonlinear optics in asymmetric double n-type δ-doped quantum well in a GaAs-matrix. • The system is considered under external applied electric field in growth direction. • The 2D impurity density is consistent with the experimental data growth regime. • The optical quantities are significantly affected by the structural asymmetry of the system.
Carrier mobility in double-helix DNA and RNA: A quantum chemistry study with Marcus-Hush theory
Wu, Tao; Sun, Lei; Shi, Qi; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng
2016-12-01
Charge mobilities of six DNAs and RNAs have been computed using quantum chemistry calculation combined with the Marcus-Hush theory. Based on this simulation model, we obtained quite reasonable results when compared with the experiment, and the obtained charge mobility strongly depends on the molecular reorganization and electronic coupling. Besides, we find that hole mobilities are larger than electron mobilities no matter in DNAs or in RNAs, and the hole mobility of 2L8I can reach 1.09 × 10-1 cm2 V-1 s-1 which can be applied in the molecular wire. The findings also show that our theoretical model can be regarded as a promising candidate for screening DNA- and RNA-based molecular electronic devices.
Carrier mobility in double-helix DNA and RNA: A quantum chemistry study with Marcus-Hush theory.
Wu, Tao; Sun, Lei; Shi, Qi; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng
2016-12-21
Charge mobilities of six DNAs and RNAs have been computed using quantum chemistry calculation combined with the Marcus-Hush theory. Based on this simulation model, we obtained quite reasonable results when compared with the experiment, and the obtained charge mobility strongly depends on the molecular reorganization and electronic coupling. Besides, we find that hole mobilities are larger than electron mobilities no matter in DNAs or in RNAs, and the hole mobility of 2L8I can reach 1.09 × 10(-1) cm(2) V(-1) s(-1) which can be applied in the molecular wire. The findings also show that our theoretical model can be regarded as a promising candidate for screening DNA- and RNA-based molecular electronic devices.
Larionov, A V; Hvam, J; Soerensen, K
2002-01-01
The time evolution and kinetics of the photoluminescence (PL) spectra of the interwall excitons under the pulse resonant excitation of the interwall excitons are studied in the GaAs/AlGaAs binary quantum well. It is established, that the collective exciton phase originates with the time delay relative to the exciting pulse (several nanoseconds), which is conditioned by the density and temperature relaxation to the equilibrium values.The origination of the collective phase of the interwall excitons is accompanied by the strong narrowing of the corresponding photoluminescence line, the superlinear growth of its intensity and large time of change in the degree of the circular polarization.The collective exciton phase originates at the temperatures < 6 K and the interwall excitons densities 3 x 10 sup 1 sup 0 cm sup - sup 2
Synthesis and intermolecular interactions of N-benzylidenetyramines
Maldonado, Mauricio; Pérez-Redondo, Adrián; Quevedo, Rodolfo
2017-01-01
In this paper, the synthesis and intermolecular interactions between N-benzylidenetyramine molecules were investigated. The crystal structure of N-(4-nitrobenzylidene)tyramine shows a molecular organization in zigzag chains with intermolecular O-H⋯N hydrogen bonds between the azomethine and phenolic hydroxyl groups. Those chains are held together by C-H⋯O hydrogen bonds to generate layers, which are connected by C-H⋯O, π⋯π and NO2⋯π interactions.
Zhang, Xiang; Mitin, Vladimir; Choi, Jae Kyu; Sablon, Kimberly; Sergeev, Andrei
2016-05-01
We designed, fabricated, and characterized multi-color IR photodetectors with asymmetrical doping of GaAs/AlGaAs double quantum wells (DQW). We measured and analyzed spectral and noise characteristics to evaluate feasibility of these photodetectors for remote temperature sensing at liquid nitrogen temperatures. The bias voltage controls the charge distribution between the two wells in a DQW unit and provides effective tuning of IR induced electron transitions. We have found that the responsivity of our devices is symmetrical and weakly dependent on the bias voltage because the doping asymmetry compensates the effect of dopant migration in the growth direction. At the same time, the asymmetrical doping strongly enhances the selectivity and tunability of spectral characteristics by bias voltage. Multicolor detection of our QWIP is realized by varying the bias voltage. Maximum detection wavelength moves from 7.5 μm to 11.1 μm by switching applied bias from -5 V to 4 V. Modeling shows significant dependence of the photocurrent ratio on the object temperature regardless of its emissivity and geometrical factors. We also experimentally investigated the feasibility of our devices for remote temperature sensing by measuring the photocurrent as a response to blackbody radiation with the temperature from 300°C to 1000°C in the range of bias voltages from -5 V to 5 V. The agreement between modelling and experimental results demonstrates that our QWIP based on asymmetrically doped GaAs/AlGaAs DQW nanomaterial is capable of remote temperature sensing. By optimizing the physical design and varying the doping level of quantum wells, we can generalize this approach to higher temperature measurements. In addition, continuous variation of bias voltage provides fast collection of large amounts of photocurrent data at various biases and improves the accuracy of remote temperature measurements via appropriate algorithm of signal processing.
Energy Technology Data Exchange (ETDEWEB)
Lopes, E.M., E-mail: eldermantovani@yahoo.com.br [Departamento de Física, Química e Biologia, Universidade Estadual Paulista, C. P. 266, Presidente Prudente, São Paulo 17700-000 (Brazil); César, D.F. [Departamento de Física, Universidade Federal de São Carlos, C. P. 676, São Carlos, São Paulo (Brazil); Franchello, F.; Duarte, J.L.; Dias, I.F.L.; Laureto, E. [Departamento de Física, Universidade Estadual de Londrina, C. P. 6001, Londrina, Paraná (Brazil); Elias, D.C.; Pereira, M.V.M.; Guimarães, P.S.S. [Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, C. P. 702, Belo Horizonte, Minas Gerais (Brazil); Quivy, A.A. [Laboratório de Novos Materiais Semicondutores, Instituto de Física, Universidade de São Paulo, C. P. 66318, São Paulo (Brazil)
2013-12-15
This paper discusses the theoretical and experimental results obtained for the excitonic binding energy (E{sub b}) in a set of single and coupled double quantum wells (SQWs and CDQWs) of GaAs/AlGaAs with different Al concentrations (Al%) and inter-well barrier thicknesses. To obtain the theoretical E{sub b} the method proposed by Mathieu, Lefebvre and Christol (MLC) was used, which is based on the idea of fractional-dimension space, together with the approach proposed by Zhao et al., which extends the MLC method for application in CDQWs. Through magnetophotoluminescence (MPL) measurements performed at 4 K with magnetic fields ranging from 0 T to 12 T, the diamagnetic shift curves were plotted and adjusted using two expressions: one appropriate to fit the curve in the range of low intensity fields and another for the range of high intensity fields, providing the experimental E{sub b} values. The effects of increasing the Al% and the inter-well barrier thickness on E{sub b} are discussed. The E{sub b} reduction when going from the SQW to the CDQW with 5 Å inter-well barrier is clearly observed experimentally for 35% Al concentration and this trend can be noticed even for concentrations as low as 25% and 15%, although the E{sub b} variations in these latter cases are within the error bars. As the Zhao's approach is unable to describe this effect, the wave functions and the probability densities for electrons and holes were calculated, allowing us to explain this effect as being due to a decrease in the spatial superposition of the wave functions caused by the thin inter-well barrier. -- Highlights: • Magnetophotoluminescence results from coupled double quantum wells are reported. • Theoretical and experimental values for excitonic binding energy (E{sub b}) are obtained. • The effects of increasing the inter-well barrier height and thickness on E{sub b} are discussed. • An E{sub b} reduction is observed when going from zero to the 5 Å inter-well barrier
Kuniba, Atsuo; Sergeev, Sergey
2014-01-01
We introduce a homomorphism from the quantum affine algebras $U_q(D^{(2)}_{n+1}), U_q(A^{(2)}_{2n}), U_q(C^{(1)}_{n})$ to the $n$-fold tensor product of the $q$-oscillator algebra ${\\mathcal A}_q$. Their action commute with the solutions of the Yang-Baxter equation obtained by reducing the solutions of the tetrahedron equation associated with the modular and the Fock representations of ${\\mathcal A}_q$. In the former case, the commutativity is enhanced to the modular double of these quantum affine algebras.
Energy Technology Data Exchange (ETDEWEB)
Gale, K.C.R.
1992-01-01
Single-stranded [phi]X174 (+) strand DNA was used as a model substrate for topoisomerase II to determine whether double-stranded DNA cleavage observed in vitro reflects the in vivo intermediate in the enzyme's catalytic cycle and to investigate potential mechanisms for topoisomerase II-mediated DNA recombination. As found previously for topoisomerase II-mediated cleavage of double-stranded DNA, the enzyme was covalently linked to the 5[prime]-termini of cleaved [phi]X174 molecules. Optimal reaction conditions were similar for the two substrates. In contrast to results with double-stranded molecules, single-stranded DNA cleavage increased with time, was not reversible, and did not require the presence of SDS. Cleavage products generated in the absence of protein denaturant contained free 3[prime]-OH DNA termini. These results strongly suggest that the covalent topoisomerase II-cleaved DNA complex observed in vitro is the active intermediate in the enzyme's catalytic code. Topoisomerase II is capable of joining cleaved [phi]X174 (+) strand DNA to duplex oligonucleotide acceptor molecules by an intermolecular ligation reaction. Intermolecular DNA ligation proceeded in a time and oligonucleotide concentration dependent fashion. The covalent linkage is between the 5[prime]-phosphate of [phi]X174 (+) strand DNA and the 3[prime]-OH of oligonucleotide acceptor molecules. The reaction was dependent on the presence of a divalent cation, was inhibited by salt, and was not affected by the presence of ATP. The enzyme was capable of ligating [phi]X174 (+) strand DNA to double-stranded oligonucleotides that contained 5[prime]-overhang, 3[prime]-overhang, or blunt ends. Single-stranded, nicked, or gapped oligonucleotides could also be used as acceptor molecules. These results demonstrate that the type II enzyme has an intrinsic ability to mediate illegitimate DNA recombination in vitro and suggests possible roles for topoisomerase II in nucleic acid recombination in vivo.
Rajak, Atanu; Divakaran, Uma
2016-04-01
We study the effect of two simultaneous local quenches on the evolution of the Loschmidt echo (LE) and entanglement entropy (EE) of a one dimensional transverse Ising model. In this work, one of the local quenches involves the connection of two spin-1/2 chains at a certain time and the other corresponds to a sudden change in the magnitude of the transverse field at a given site in one of the spin chains. We numerically calculate the dynamics associated with the LE and the EE as a result of such double quenches, and discuss the various timescales involved in this problem using the picture of quasiparticles (QPs) generated as a result of such quenches. We perform a detailed analysis of the probability of QPs produced at the two sites and the nature of the QPs in various phases, and obtain interesting results. More specifically, we find partial reflection of these QPs at the defect center or the site of h-quench, resulting in new timescales which have never been reported before.
Energy Technology Data Exchange (ETDEWEB)
Thantu, Napoleon; McMorrow, D.; Melinger, J. S.; Kleiman, V.; Lotshaw, W. T.
2001-07-01
The apparently-multicomponent subpicosecond intermolecular dynamics of carbon disulfide liquid are addressed in a unified manner in terms of an inhomogeneously broadened quantum mechanical harmonic oscillator model for a single vibrational coordinate. For an inhomogeneously broadened (Gaussian) distribution of oscillators, the model predicts naturally the bimodal character of the subpicosecond intermolecular dynamics of carbon disulfide liquid, and also the spectral evolution effects (spectral narrowing and saturation) that are observed for solutions of carbon disulfide in weakly interacting alkane solvents. The unique dynamical signature of these low-frequency vibrational coordinates is determined largely by the physical constraints on the coordinates (near equality of oscillator frequency, dephasing frequency, and inhomogeneous bandwidth), such that constructive and destructive interference effects play a dominant role in shaping the experimental observable.
Kominis, Iannis
2011-03-01
Radical-ion-pair reactions, fundamental in photosynthesis and at the basis of the avian magnetic compass mechanism, have been recently shown to offer a rich playground for applying methods and concepts from quantum measurement/quantum information science. We will demonstrate that radical-ion-pair reactions are almost the exact analog of the optical double slit experiment, i.e. Nature has already engineered biochemical reactions performing the act of quantum interference. We will further elaborate on the non-trivial quantum effects pertaining in these reactions and the recent debate on their fundamental theoretical description that these effects have sparked.
Morgenstern Horing, Norman J.; Popov, Vyacheslav V.
2006-04-01
Recent experimental observations by X.G. Peralta and S.J. Allen, et al. of dc photoconductivity resonances in steady source-drain current subject to terahertz radiation in a grid-gated double-quantum well FET suggested an association with plasmon resonances. This association was definitively confirmed for some parameter ranges in our detailed electrodynamic absorbance calculations. In this paper we propose that the reason that the dc photoconductance resonances match the plasmon resonances in semiconductors is based on a nonlinear dynamic screening mechanism. In this, we employ a shielded potential approximation that is nonlinear in the terahertz field to determine the nonequilibrium Green's function and associated density perturbation that govern the nonequilibrium dielectric polarization of the medium. This ''conditioning'' of the system by the incident THz radiation results in resonant polarization response at the plasmon frequencies which, in turn, causes a sharp drop of the resistive shielded impurity scattering potentials and attendant increase of the dc source-drain current. This amounts to disabling the impurity scattering mechanism by plasmon resonant behavior in nonlinear screening.
Wang, Lin-Wei; Qu, Ai-Ping; Liu, Wen-Lou; Chen, Jia-Mei; Yuan, Jing-Ping; Wu, Han; Li, Yan; Liu, Juan
2016-02-01
As a widely used proliferative marker, Ki67 has important impacts on cancer prognosis, especially for breast cancer (BC). However, variations in analytical practice make it difficult for pathologists to manually measure Ki67 index. This study is to establish quantum dots (QDs)-based double imaging of nuclear Ki67 as red signal by QDs-655, cytoplasmic cytokeratin (CK) as yellow signal by QDs-585, and organic dye imaging of cell nucleus as blue signal by 4‧,6-diamidino-2-phenylindole (DAPI), and to develop a computer-aided automatic method for Ki67 index measurement. The newly developed automatic computerized Ki67 measurement could efficiently recognize and count Ki67-positive cancer cell nuclei with red signals and cancer cell nuclei with blue signals within cancer cell cytoplasmic with yellow signals. Comparisons of computerized Ki67 index, visual Ki67 index, and marked Ki67 index for 30 patients of 90 images with Ki67 ≤ 10% (low grade), 10% dye imaging on BC tissues, this study successfully developed an automatic computerized Ki67 counting method to measure Ki67 index.
Maruyoshi, Keisuke; Iuga, Dinu; Watts, Abigail E; Hughes, Colan E; Harris, Kenneth D M; Brown, Steven P
2017-07-25
The lower detection limit for 2 distinct crystalline phases by (1)H magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is investigated for a minority amount of cimetidine (anhydrous polymorph A) in a physical mixture with the anhydrous HCl salt of cimetidine. Specifically, 2-dimensional (1)H double-quantum (DQ) MAS NMR spectra of polymorph A and the anhydrous HCl salt constitute fingerprints for the presence of each of these solid forms. For solid-state NMR data recorded at a (1)H Larmor frequency of 850 MHz and a MAS frequency of 30 kHz on ∼10 mg of sample, it is shown that, by following the pair of cross-peaks at a (1)H DQ frequency of 7.4 + 11.6 = 19.0 ppm that are unique to polymorph A, the level of detection for polymorph A in a physical mixture with the anhydrous HCl salt is a concentration of 1% w/w. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Tang, Yanqun; Wang, Ruirui; Yang, Ye; Yan, Dongpeng; Xiang, Xu
2016-08-03
The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is -1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.
Feng, Jijun; Akimoto, Ryoichi; Gozu, Shin-ichiro; Mozume, Teruo; Hasama, Toshifumi; Ishikawa, Hiroshi
2013-07-01
We demonstrate a compact all-optical Michelson interferometer (MI) gating switch with monolithic integration of two different bandgap energies. Based on the ion-induced intermixing in InGaAs/AlAsSb coupled double quantum wells, the blueshift of the band edge can be tailored. Through phosphorus ion implantation with a dose of 5 × 10(14) cm(-2) and subsequent annealing at 720 °C for 60 s, an implanted sample can acquire a high transmittance compared with the as-grown one. Meanwhile, the cross-phase modulation (XPM) efficiency of a non-implanted sample undergoing the same annealing process decreases little. An implanted part for signal propagation and a non-implanted section for XPM are thus monolithically integrated for an MI switch by an area-selective manner. Full switching of a π-rad nonlinear phase shift is achieved with pump pulse energy of 5.6 pJ at a 10-GHz repetition rate.
Institute of Scientific and Technical Information of China (English)
Cen Long-Bin; Shen Bo; qin Zhi-Xin; Zhang Guo-Yi
2009-01-01
The influence of applied electric fields on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells (CDQWs) has been investigated by solving Schrodinger and Poisson equations self-consistently. It is found that the absorption coefficient of the intersubband transition (ISBT) between the ground state and the third excited state (1odd -2even) can be equal to zero when the electric fields are applied in asymmetrical A1N/GaN CDQWs,which is related to applied electric fields induced symmetry recovery of these states. Meanwhile,the energy distances between 1odd -2even and 1even - 2even subbands have different relationships from each other with the increase of applied electric fields due to the different polarization-induced potential drops between the lett and the right wells. The results indicate that an electrical-optical modulator operated within the opto-communication wavelength range can be realized in spite of the strong polarization-induced electric fields in asymmetrical AIN/GaN CDQWs.
Liu, Peng; Zhang, Jingxue; Wang, Dunyou
2017-06-07
A double-inversion mechanism of the F(-) + CH3I reaction was discovered in aqueous solution using combined multi-level quantum mechanics theories and molecular mechanics. The stationary points along the reaction path show very different structures to the ones in the gas phase due to the interactions between the solvent and solute, especially strong hydrogen bonds. An intermediate complex, a minimum on the potential of mean force, was found to serve as a connecting-link between the abstraction-induced inversion transition state and the Walden-inversion transition state. The potentials of mean force were calculated with both the DFT/MM and CCSD(T)/MM levels of theory. Our calculated free energy barrier of the abstraction-induced inversion is 69.5 kcal mol(-1) at the CCSD(T)/MM level of theory, which agrees with the one at 72.9 kcal mol(-1) calculated using the Born solvation model and gas-phase data; and our calculated free energy barrier of the Walden inversion is 24.2 kcal mol(-1), which agrees very well with the experimental value at 25.2 kcal mol(-1) in aqueous solution. The calculations show that the aqueous solution makes significant contributions to the potentials of mean force and exerts a big impact on the molecular-level evolution along the reaction pathway.
Yan, Yun-Jing; He, Xi-Wen; Li, Wen-You; Zhang, Yu-Kui
2017-05-15
A novel fluorescent sensor nitrogen-doped graphene quantum dots (N-GQDs)/SiO2/molecular imprinting polymer（N-GQDs/SiO2/MIP）was fabricated by surface imprinting and epitope imprinting to recognize and detect the target protein cytochrome c (Cyt C) with fluorescence quenching. In the polymerization process, the C- and N-terminal nonapeptides of Cyt C were selected as the double templates which were fixed by functional monomer (zinc acrylate) through metal chelation and steady six-membered ring. The linear range of fluorescence quenching for this receptor towards Cyt C was 0.20-60μM, and the detection limit was 0.11μM. The precision for six times replicate determination of Cyt C at 30μM was 1.20%, and the imprinting factor (IF) was 3.06. The recoveries of the material to Cyt C in urine were 99.3-114.0%. In brief, this work proposed a strategy to prepare a new type fluorescent imprinting polymer based on N-GQDs and provided an attractive perspective for the detection of protein by using the combination of N-GQDs and molecular imprinting technique.
Energy Technology Data Exchange (ETDEWEB)
Azar, Richard Julian, E-mail: julianazar2323@berkeley.edu; Head-Gordon, Martin, E-mail: mhg@cchem.berkeley.edu [Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2015-05-28
Your correspondents develop and apply fully nonorthogonal, local-reference perturbation theories describing non-covalent interactions. Our formulations are based on a Löwdin partitioning of the similarity-transformed Hamiltonian into a zeroth-order intramonomer piece (taking local CCSD solutions as its zeroth-order eigenfunction) plus a first-order piece coupling the fragments. If considerations are limited to a single molecule, the proposed intermolecular similarity-transformed perturbation theory represents a frozen-orbital variant of the “(2)”-type theories shown to be competitive with CCSD(T) and of similar cost if all terms are retained. Different restrictions on the zeroth- and first-order amplitudes are explored in the context of large-computation tractability and elucidation of non-local effects in the space of singles and doubles. To accurately approximate CCSD intermolecular interaction energies, a quadratically growing number of variables must be included at zeroth-order.
Intermolecular Interaction of HMX:an Application of ONIOM Methodology
Institute of Scientific and Technical Information of China (English)
JU Xue-hai; BEI Feng-li; XIA Qi-ying; XIAO He-ming
2004-01-01
Ab initio calculations at the B3LYP/3-21G * *, HF/3-21G＞** and ONIOM(HF/3-21G* * : AM1) levels of the theory in combination with counterpoise procedure for BSSE correction were performed on HMX dimers. There exist two O…H intermolecular contacts and the dispersion forces are dominant in the dimers.The corrected binding energies of the dimer are -15.10 and -17.81 kJ/mol at the HF/3-21G** and ONIOM(HF/3-21G**: AM1)levels, respectively. The calculation by the B3LYP method gives irrational corrected binding energies though it produces similar intermolecular distances as those produced by the HF or ONIOM method. The geometrical parameters, the contact distances and the binding energies demonstrated,for the first time, the validity of the ONIOM method applied in the calculation of the parameters of intermolecular interactions.
Lee, J M; Jeon, B H; Kim, J; Lee, D
2015-12-14
We investigated the microscopic mechanism underlying the double-state lasing behavior (simultaneous lasing at the ground state [GS] and excited state [ES]) in InAs/GaAs quantum dot (QD) laser diodes. The ES and GS lasing processes that contributed to double-state lasing were examined experimentally and theoretically. Experiments were conducted in which spontaneous emission from a window of a QD laser diode was examined under lasing conditions, and numerical simulations were performed using a coupled rate equation model of the QD microstates. The findings showed that, when carrier relaxation from the ES to the GS was sufficiently slow, double-state lasing occurred. Additionally, ES lasing was found to arise not from the QD group undergoing GS lasing, but rather from another QD group in which the states were lower in energy and outside of the homogeneous bandwidth.
Ab initio intermolecular potential energy surface and thermophysical properties of nitrous oxide
Energy Technology Data Exchange (ETDEWEB)
Crusius, Johann-Philipp, E-mail: johann-philipp.crusius@uni-rostock.de; Hassel, Egon [Lehrstuhl für Technische Thermodynamik, Universität Rostock, 18059 Rostock (Germany); Hellmann, Robert, E-mail: robert.hellmann@uni-rostock.de; Bich, Eckard [Institut für Chemie, Universität Rostock, 18059 Rostock (Germany)
2015-06-28
We present an analytical intermolecular potential energy surface (PES) for two rigid nitrous oxide (N{sub 2}O) molecules derived from high-level quantum-chemical ab initio calculations. Interaction energies for 2018 N{sub 2}O–N{sub 2}O configurations were computed utilizing the counterpoise-corrected supermolecular approach at the CCSD(T) level of theory using basis sets up to aug-cc-pVQZ supplemented with bond functions. A site-site potential function with seven sites per N{sub 2}O molecule was fitted to the pair interaction energies. We validated our PES by computing the second virial coefficient as well as shear viscosity and thermal conductivity in the dilute-gas limit. The values of these properties are substantiated by the best experimental data.
Intermolecular stabilization of 3,3'-diamino-4,4'-azoxyfurazan (DAAF) compressed to 20 GPa.
Chellappa, Raja S; Dattelbaum, Dana M; Coe, Joshua D; Velisavljevic, Nenad; Stevens, Lewis L; Liu, Zhenxian
2014-08-07
The room temperature stability of 3,3'-diamino-4,4'-azoxyfurazan (DAAF) has been investigated using synchrotron far-infrared, mid-infrared, Raman spectroscopy, and synchrotron X-ray diffraction (XRD) up to 20 GPa. The as-loaded DAAF samples exhibited subtle pressure-induced ordering phenomena (associated with positional disorder of the azoxy "O" atom) resulting in doubling of the a-axis, to form a superlattice similar to the low-temperature polymorph. Neither high pressure synchrotron XRD, nor high pressure infrared or Raman spectroscopies indicated the presence of structural phase transitions up to 20 GPa. Compression was accommodated in the unit cell by a reduction of the c-axis between the planar DAAF layers, distortion of the β-angle of the monoclinic lattice, and an increase in intermolecular hydrogen bonding. Changes in the ring and -NH2 deformation modes and increased intermolecular hydrogen bonding interactions with compression suggest molecular reorganizations and electronic transitions at ∼ 5 GPa and ∼ 10 GPa that are accompanied by a shifting of the absorption band edge into the visible. A fourth-order Birch-Murnaghan fit to the room temperature isotherm afforded an estimate of the zero-pressure isothermal bulk modulus, K0 = 12.4 ± 0.6 GPa and its pressure derivative K0' = 7.7 ± 0.3.
Ionic strength and intermolecular contacts in protein crystals
Iyer, Ganesh H.; Dasgupta, Swagata; Bell, Jeffrey A.
2000-08-01
The ionic strengths of crystallization solutions for 206 proteins were observed to form a bimodal distribution. The data was divided into two sets at an ionic strength of 4.4 M, and knowledge-based potentials were calculated to determine contact preferences at intermolecular crystal interfaces. Consistent with previous observations over all ionic strengths, intermolecular crystal contacts tend to exclude nonpolar amino acids; lysine is the least favored polar amino acid at crystal contacts; and arginine and glutamine are the two most favored amino acid at crystal contacts. However, some aspects of intermolecular contact preferences within protein crystals are significantly dependent on ionic strength. Arginine is the most favored residue at low ionic strength, but it takes second place to glutamine at high ionic strength. Other major ionic strength-dependent differences in protein crystal contacts can be explained by the binding of cations or anions. While others have shown the importance of ion binding experimentally in selected protein crystals, these statistical results indicate that intermolecular interface formation must involve ion-mediated contacts in a large number of protein crystals.
Connecting Protein Structure to Intermolecular Interactions: A Computer Modeling Laboratory
Abualia, Mohammed; Schroeder, Lianne; Garcia, Megan; Daubenmire, Patrick L.; Wink, Donald J.; Clark, Ginevra A.
2016-01-01
An understanding of protein folding relies on a solid foundation of a number of critical chemical concepts, such as molecular structure, intra-/intermolecular interactions, and relating structure to function. Recent reports show that students struggle on all levels to achieve these understandings and use them in meaningful ways. Further, several…
Intermolecular Phosphoryl Transfer Between Serine and Histidine Residues
Institute of Scientific and Technical Information of China (English)
Yu Qian SU; Ming Yu NIU; Shu Xia CAO; Jian Chen ZHANG; Yu Fen ZHAO
2004-01-01
A novel intermolecular phosphoryl transfer from O-trimethylsilyl-N-(O, O-diisopropyl) phosphoryl serine trimethylsilyl ester to N, N'-bis(trimethylsilyl) histidine trimethylsilyl ester was studied through electrospray ionization mass spectrometry (ESI-MS). It was proposed that the transfer reaction went through penta-coordinated phosphorus intermediate.
Intermolecular Interactions in Ternary Glycerol–Sample–H2O
DEFF Research Database (Denmark)
Westh, Peter; Rasmussen, Erik Lumby; Koga, Yoshikata
2011-01-01
We studied the intermolecular interactions in ternary glycerol (Gly)–sample (S)–H2O systems at 25 °C. By measuring the excess partial molar enthalpy of Gly, HGlyEHEGly, we evaluated the Gly–Gly enthalpic interaction, HGly-GlyEHEGly--Gly, in the presence of various samples (S). For S, tert...
Learning about Intermolecular Interactions from the Cambridge Structural Database
Battle, Gary M.; Allen, Frank H.
2012-01-01
A clear understanding and appreciation of noncovalent interactions, especially hydrogen bonding, are vitally important to students of chemistry and the life sciences, including biochemistry, molecular biology, pharmacology, and medicine. The opportunities afforded by the IsoStar knowledge base of intermolecular interactions to enhance the…
Intermolecular atom-atom bonds in crystals - a chemical perspective.
Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R
2015-03-01
Short atom-atom distances between molecules are almost always indicative of specific intermolecular bonding. These distances may be used to assess the significance of all hydrogen bonds, including the C-H⋯O and even weaker C-H⋯F varieties.
Learning about Intermolecular Interactions from the Cambridge Structural Database
Battle, Gary M.; Allen, Frank H.
2012-01-01
A clear understanding and appreciation of noncovalent interactions, especially hydrogen bonding, are vitally important to students of chemistry and the life sciences, including biochemistry, molecular biology, pharmacology, and medicine. The opportunities afforded by the IsoStar knowledge base of intermolecular interactions to enhance the…
Student Understanding of Intermolecular Forces: A Multimodal Study
Cooper, Melanie M.; Williams, Leah C.; Underwood, Sonia M.
2015-01-01
The ability to use representations of molecular structure to predict the macroscopic properties of a substance is central to the development of a robust understanding of chemistry. Intermolecular forces (IMFs) play an important role in this process because they provide a mechanism for how and why molecules interact. In this study, we investigate…
Dancing Crystals: A Dramatic Illustration of Intermolecular Forces
Mundell, Donald W.
2007-01-01
Crystals of naphthalene form on the surface of an acetone solution and dance about in an animated fashion illustrating surface tension, crystallization, and intermolecular forces. Additional experiments reveal the properties of the solution. Flows within the solutions can be visualized by various means. Previous demonstrations of surface motion…
DEFF Research Database (Denmark)
Hanni, Matti; Lantto, Perttu; Ilias, Miroslav
2007-01-01
Relativistic effects on the 129Xe nuclear magnetic resonance shielding and 131Xe nuclear quadrupole coupling (NQC) tensors are examined in the weakly bound Xe2 system at different levels of theory including the relativistic four-component Dirac-Hartree-Fock (DHF) method. The intermolecular...... interaction-induced binary chemical shift d, the anisotropy of the shielding tensor ?s, and the NQC constant along the internuclear axis ?ll are calculated as a function of the internuclear distance. DHF shielding calculations are carried out using gauge-including atomic orbitals. For comparison, the full...... leading-order one-electron Breit-Pauli perturbation theory (BPPT) is applied using a common gauge origin. Electron correlation effects are studied at the nonrelativistic (NR) coupled-cluster singles and doubles with perturbational triples [CCSD(T)] level of theory. The fully relativistic second...
2015-01-01
Allenes are important 2π building blocks in organic synthesis and engage as 2-carbon components in many metal-catalyzed reactions. Wender and co-workers discovered that methyl substituents on the terminal allene double bond counterintuitively change the reactivities of allenes in [Rh(CO)2Cl]2-catalyzed intermolecular (5 + 2) cycloadditions with vinylcyclopropanes (VCPs). More sterically encumbered allenes afford higher cycloadduct yields, and such effects are also observed in other Rh(I)-catalyzed intermolecular cycloadditions. Through density functional theory calculations (B3LYP and M06) and experiment, we explored this enigmatic reactivity and selectivity of allenes in [Rh(CO)2Cl]2-catalyzed intermolecular (5 + 2) cycloadditions with VCPs. The apparent low reactivity of terminally unsubstituted allenes is associated with a competing allene dimerization that irreversibly sequesters rhodium. With terminally substituted allenes, steric repulsion between the terminal substituents significantly increases the barrier of allene dimerization while the barrier of the (5 + 2) cycloaddition is not affected, and thus the cycloaddition prevails. Computation has also revealed the origin of chemoselectivity in (5 + 2) cycloadditions with allene-ynes. Although simple allene and acetylene have similar reaction barriers, intermolecular (5 + 2) cycloadditions of allene-ynes occur exclusively at the terminal allene double bond. The terminal double bond is more reactive due to the enhanced d−π* backdonation. At the same time, insertion of the internal double bond of an allene-yne has a higher barrier as it would break π conjugation. Substituted alkynes are more difficult to insert compared with acetylene, because of the steric repulsion from the additional substituents. This leads to the greater reactivity of the allene double bond relative to the alkynyl group in allene-ynes. PMID:25379606
Energy Technology Data Exchange (ETDEWEB)
Huebel, A.
2007-11-22
In this work, a double quantum dot system is studied whose two dots are electrically insulated from one another and contacted independently with two leads. The geometry is optimized to maximize the capacitive interaction between the dots. The samples are characterized by electrical transport measurements in a dilution refrigerator. It is then studied at different tunnel couplings how the capacitive interaction influences the electrical transport in equilibrium. Under certain conditions correlated tunnel processes can be observed. A simple model is derived that serves to understand these processes. The double quantum dot system is defined in lateral arrangement by reactive ion etching of a two-dimensional electron system located only 50 nm below the surface of a GaAs-AlGaAs heterostructure. The samples are characterized in a dilution refrigerator at 25 mK near the common pinch-off point of all four tunnel barriers. A measurement of the differential equilibrium conductances of both quantum dots as a function of two gate voltages yields a honeycomb-like charge stability diagram. The most important sample characteristic is the ratio between the interaction capacitance and the total capacitance of a single quantum dot. For the optimized sample, this ratio turns out to be larger than one third near the common pinch-off point, with a single-dot charging energy of up to 800 {mu}eV. At more positive gate voltages, the capacitances between the quantum dots and their leads increase more and more, thereby diminishing the charging energy. It is shown for the optimized sample that all capacitance coefficients except the dot-lead capacitances are constant to within considerable accuracy over several Coulomb blockade oscillations. In order to measure correlated electrical transport in equilibrium, special parameter regions are examined in which the charges of both quantum dots cannot fluctuate independently of each other. An analytical formula is derived that describes the
Asymmetry of hole states in vertically coupled Ge double quantum dot%耦合锗量子点中空穴态对称特性研究
Institute of Scientific and Technical Information of China (English)
崔尉; 王茺; 崔灿; 施张胜; 杨宇
2014-01-01
The two lowest single-particle hole states in the vertically coupled Ge/Si double layer quantum dots are investigated numerically by using the single-band heavy hole effective mass approximation and six-band Kronig-Penney model, re-spectively. The calculated results indicate that within the frame of several-band coupled model, the bonding-antibonding ground-state transition and a bonding-antibonding energy anti-crossover phenomenon are observed with interdot dis-tance increasing. These results have not been observed previously in those single-band model calculations. The analysis of the wavefunction component of bonding-antibonding hole state shows that the contribution ratios of light, heavy and spin-orbital-split-off hole states to the characteristic hole wavefunction vary with the increase of the vertical coupled distance, resulting in the ground state wavefunction changing from bonding states to antibonding ones finally.%分别采用单带重空穴近似和六带Kronig-Penney模型，对垂直耦合锗量子点在不同耦合距离下的空穴态特性进行了计算，并探讨了自旋-轨道的相互作用对空穴态对称性的影响。计算结果表明：多带耦合的框架下，随着量子点垂直间距的增大，空穴基态从成键态转变为反键态，而且价带基态能级和第一激发态能级发生反交叉现象，这与单带模型下得到的相应结果存在较大差异。通过分析六带模型计算得到的成、反键态波函数，轻、重空穴态和自旋-轨道分裂态对特征空穴态波函数的贡献比例随着量子点垂直间距的增大发生了转变，并最终导致量子点空穴基态波函数由成键态转变为反键态。
Energy Technology Data Exchange (ETDEWEB)
Baghramyan, H.M. [Department of Solid State Physics, Yerevan State University, Alex Manoogian 1, 0025 Yerevan (Armenia); Barseghyan, M.G., E-mail: mbarsegh@ysu.am [Department of Solid State Physics, Yerevan State University, Alex Manoogian 1, 0025 Yerevan (Armenia); Kirakosyan, A.A. [Department of Solid State Physics, Yerevan State University, Alex Manoogian 1, 0025 Yerevan (Armenia); Laroze, D. [Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, Arica (Chile); Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)
2014-09-15
The donor-impurity related photoionization cross section in GaAs/Ga{sub 1−x}Al{sub x}As three-dimensional concentric double quantum rings is investigated. The photoionization cross section dependence on the incident photon energy is studied considering the effects of hydrostatic pressure, variations of aluminum concentration, geometries of the structure, and impurity position. The interpretation of the dipole matrix element, which reflects the photoionization probability, is also given. We have found that these parameters can lead to both redshift and blueshift of the photoionization spectrum and also influence the cross section peak value.
Energy Technology Data Exchange (ETDEWEB)
Odhiambo Oyoko, H. [Department of Physics, Westville Campus, University of KwaZulu-Natal, Private Bag X 54001, Durban 4000 (South Africa); Porras-Montenegro, N. [Departamento de Fisica, Universidad del Valle, AA 25360, Cali (Colombia); Lopez, S.Y. [Facultad de Educacion, Universidad de Antioquia, AA 1226, Medellin (Colombia); Duque, C.A. [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia)
2007-07-01
Using a variational technique within the effective mass approximation we have carried out a comparative study of the effect of hydrostatic pressure and temperature on the shallow-impurity related optical absorption spectra in GaAs-Ga{sub 1-x}Al{sub x}As single and double quantum wells. The results show a pressure dependent read-shift and a temperature dependent blue-shift in the optical absorption spectra. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Abayev, Meital; Srivastava, Gautam; Arshava, Boris; Naider, Fred; Anglister, Jacob
2017-02-01
NMR is a powerful tool for studying structural details of protein/peptide complexes exhibiting weak to medium binding (KD > 10 μm). However, it has been assumed that intermolecular nuclear Overhauser effect (NOE) interactions are difficult to observe in such complexes. We demonstrate that intermolecular NOEs can be revealed by combining the (13) C-edited/(13) C-filtered experiment with the transferred NOE effect (TRNOE). Due to the TRNOE phenomenon, intermolecular NOE cross peaks are characterized by both the chemical shifts (CSs) of the protein protons and the average CSs of the peptide protons, which are dominated by the CSs of the protons of the free peptide. Previously, the TRNOE phenomenon was used almost exclusively to investigate the conformation of small ligands bound to large biomolecules. Here, we demonstrate that TRNOE can be extended to enable the study of intermolecular interactions in small- and medium-sized protein complexes. We used the (13) C-edited/(13) C-filtered TRNOE experiment to study the interactions of the chemokine regulated upon activation, normal T cell, expressed and secreted (RANTES) with a 27-residue peptide, containing two sulfotyrosine residues, representing the N-terminal segment of the CCR5 receptor ((Nt-CCR5(1-27). The TRNOE phenomenon led to more than doubling of the signal-to-noise ratios (SNRs) for the intermolecular NOEs observed in the (13) C-edited/(13) C-filtered experiment for the 11.5-kDa monomeric RANTES/Nt-CCR5(1-27) complex. An even better improvement in the SNR was achieved with dimeric Nt-CCR5(1-27)/RANTES (23 kDa), especially in comparison with the spectra measured with a 1 : 1 protein to peptide ratio. In principle, the isotope-edited/isotope-filtered TRNOE spectrum can discern all intermolecular interactions involving nonexchangeable protons in the complex. © 2017 Federation of European Biochemical Societies.
Intramolecular versus intermolecular disulfide bonds in prion proteins.
Welker, Ervin; Raymond, Lynne D; Scheraga, Harold A; Caughey, Byron
2002-09-01
Prion protein (PrP) is the major component of the partially protease-resistant aggregate that accumulates in mammals with transmissible spongiform encephalopathies. The two cysteines of the scrapie form, PrP(Sc), were found to be in their oxidized (i.e. disulfide) form (Turk, E., Teplow, D. B., Hood, L. E., and Prusiner, S. B. (1988) Eur. J. Biochem. 176, 21-30); however, uncertainty remains as to whether the disulfide bonds are intra- or intermolecular. It is demonstrated here that the monomers of PrP(Sc) are not linked by intermolecular disulfide bonds. Furthermore, evidence is provided that PrP(Sc) can induce the conversion of the oxidized, disulfide-intact form of the monomeric cellular prion protein to its protease-resistant form without the temporary breakage and subsequent re-formation of the disulfide bonds in cell-free reactions.
Intermolecular Hydrogen Bonding in Peptide and Modified Jeffamine Organogels
Savin, Daniel; Richardson, Adam
2011-03-01
In these studies, we present two systems whereby supramolecular assembly results in rigid organogels. First, a series of AB diblock copolymers consisting of poly(Lysine(Z)) (P(Lys(Z)) blocks were synthesized and found to form stable, rigid organogels in THF (ca. 1 - 1.5 wt.% solutions) and chloroform at room temperature. In these systems, the protecting group on the P(Lys) side-chains remains intact and gel formation results from the assembly of the solventphobic P(Lys(Z)) chains through intermolecular beta-sheet formation. The non-peptide block was found to have an effect on organogel properties due to interfacial frustration, which disrupts H-bonding. Second, Jeffamine polymers were modified in a facile way to incorporate intermolecular H-bonding groups to yield networks able to gel various solvents as well as mineral and canola oil. We present the physical and rheological properties of the organogels produced.
The Nature of Intermolecular Interactions Between Aromatic Amino Acid Residues
Energy Technology Data Exchange (ETDEWEB)
Gervasio, Francesco; Chelli, Riccardo; Procacci, Piero; Schettino, Vincenzo
2002-05-01
The nature of intermolecular interactions between aromatic amino acid residues has been investigated by a combination of molecular dynamics and ab initio methods. The potential energy surface of various interacting pairs, including tryptophan, phenilalanine, and tyrosine, was scanned for determining all the relevant local minima by a combined molecular dynamics and conjugate gradient methodology with the AMBER force field. For each of these minima, single-point correlated ab initio calculations of the binding energy were performed. The agreement between empirical force field and ab initio binding energies of the minimum energy structures is excellent. Aromatic-aromatic interactions can be rationalized on the basis of electrostatic and van der Waals interactions, whereas charge transfer or polarization phenomena are small for all intermolecular complexes and, particularly, for stacked structures.
Investigating Intermolecular Interactions in Crystalline Aspirin Using CDFT
Turner, Nicholas; Li, Tonglei; Zhang, Mingtao
2013-01-01
Drugs today are widely administered in their crystalline form, namely via tablets and capsules. The crystal structure of a drug molecule affects important drug qualities such as solubility, bioavailability, shelf life, and compaction properties. In order to form a basis for crystal structure prediction, it is necessary to first understand how intermolecular interactions cause molecules to pack in certain ways. Being able to predict and perhaps even control a drug molecule’s crystal structure ...
A New Intermolecular Phosphoryl Transfer between Serine and Histidine Residues
Institute of Scientific and Technical Information of China (English)
SU,Yu-Qian; NIU,Ming-Yu; CAO,Shu-Xia; ZHANG,Jian-Chen; QU,Ling-Bo; LIAO,Xin-Cheng; ZHAO,Yu-Fen
2004-01-01
@@ Phosphoryl transfer constitutes one of the most important reactions in functionalized molecules, bioorganic chemistry and biochemistry.[1] The transformations are involved in diverse processes, such as activated state change of phosphorus, DNA/RNA synthesis, energy metabolism and signal transduction. So, phosphoryl transfer reaction which can be performed by either intramolecular or intermolecular phosphorylation and dephosphorylation mechanism has been investigated by many scientists in wide fields.
Transient grating study of the intermolecular dynamics of liquid nitrobenzene
Wu, Hong-Lin; Song, Yun-Fei; Yu, Guo-Yang; Yang, Yan-Qiang
2016-10-01
Femtosecond time-resolved transient grating (TG) technique is used to study the intermolecular dynamics in liquid phase. Non-resonant excitation of the sample by two crossing laser pulses results in a transient Kerr grating, and the molecular motion of liquid can be detected by monitoring the diffraction of a third time-delayed probe pulse. In liquid nitrobenzene (NB), three intermolecular processes are observed with lifetimes of 37.9±1.4 ps, 3.28±0.11 ps, and 0.44±0.03 ps, respectively. These relaxations are assigned to molecular orientational diffusion, dipole/induced dipole interaction, and libration in liquid cage, respectively. Such a result is slightly different from that obtained from OKE experiment in which the lifetime of the intermediate process is measured to be 1.9 ps. The effects of electric field on matter are different in TG and optical Kerr effect (OKE) experiments, which should be responsible for the difference between the results of these two types of experiments. The present work demonstrates that TG technique is a useful alternative in the study of intermolecular dynamics. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304058 and 11404307) and NSAF (Grant No. U1330106).
McKenzie, S; Kang, H C
2014-12-21
The behavior of water confined at the nanoscale between graphene sheets has attracted much theoretical and experimental attention recently. However, the interactions, structure, and energy of water at the molecular scale underpinning the behavior of confined water have not been characterized by first-principles calculations. In this work we consider small water clusters up to the hexamer adsorbed between graphene sheets using density functional theory calculations with van der Waals corrections. We investigate the effects on structure, energy, and intermolecular interactions due to confinement between graphene sheets. For interlayer distances of about one nanometer or more, the cluster adsorption energy increases approximately linearly with the cluster size by 0.1 eV per molecule in the cluster. As the interlayer distance decreases, the cluster adsorption energy reaches a maximum at 6 to 7 Å with approximately 0.16 eV stabilization energy relative to large interlayer distances. This suggests the possibility of controlling the amount of adsorption in graphene nanomaterials by varying the interlayer distance. We also quantify the intermolecular hydrogen bonding in the clusters by calculating the dissociation energy required to remove one molecule from each cluster. For each cluster size, this is constant for interlayer distances larger than approximately 6 to 8 Å. For smaller distances the intermolecular interaction decreases rapidly thus leading to weaker cohesion between molecules in a squeezed cluster. We expect a mechanism of concerted motion for hydrogen-bonded water molecules confined between graphene sheets, as has been observed for water confined within the carbon nanotubes. Thus, the decrease in the dissociation energy we observed here is consistent with experimental results for water transport through graphene and related membranes that are of interest in nanofiltration. We also calculate the corrugation in the interaction potential between graphene
Graham, Kenneth
2014-07-09
The performance of organic photovoltaic (OPV) material systems are hypothesized to depend strongly on the intermolecular arrangements at the donor:fullerene interfaces. A review of some of the most efficient polymers utilized in polymer:fullerene PV devices, combined with an analysis of reported polymer donor materials wherein the same conjugated backbone was used with varying alkyl substituents, supports this hypothesis. Specifically, the literature shows that higher-performing donor-acceptor type polymers generally have acceptor moieties that are sterically accessible for interactions with the fullerene derivative, whereas the corresponding donor moieties tend to have branched alkyl substituents that sterically hinder interactions with the fullerene. To further explore the idea that the most beneficial polymer:fullerene arrangement involves the fullerene docking with the acceptor moiety, a family of benzo[1,2-b:4,5-b]dithiophene-thieno[3,4-c]pyrrole-4,6-dione polymers (PBDTTPD derivatives) was synthesized and tested in a variety of PV device types with vastly different aggregation states of the polymer. In agreement with our hypothesis, the PBDTTPD derivative with a more sterically accessible acceptor moiety and a more sterically hindered donor moiety shows the highest performance in bulk-heterojunction, bilayer, and low-polymer concentration PV devices where fullerene derivatives serve as the electron-accepting materials. Furthermore, external quantum efficiency measurements of the charge-transfer state and solid-state two-dimensional (2D) 13C{1H} heteronuclear correlation (HETCOR) NMR analyses support that a specific polymer:fullerene arrangement is present for the highest performing PBDTTPD derivative, in which the fullerene is in closer proximity to the acceptor moiety of the polymer. This work demonstrates that the polymer:fullerene arrangement and resulting intermolecular interactions may be key factors in determining the performance of OPV material systems
Graham, Kenneth R; Cabanetos, Clement; Jahnke, Justin P; Idso, Matthew N; El Labban, Abdulrahman; Ngongang Ndjawa, Guy O; Heumueller, Thomas; Vandewal, Koen; Salleo, Alberto; Chmelka, Bradley F; Amassian, Aram; Beaujuge, Pierre M; McGehee, Michael D
2014-07-09
The performance of organic photovoltaic (OPV) material systems are hypothesized to depend strongly on the intermolecular arrangements at the donor:fullerene interfaces. A review of some of the most efficient polymers utilized in polymer:fullerene PV devices, combined with an analysis of reported polymer donor materials wherein the same conjugated backbone was used with varying alkyl substituents, supports this hypothesis. Specifically, the literature shows that higher-performing donor-acceptor type polymers generally have acceptor moieties that are sterically accessible for interactions with the fullerene derivative, whereas the corresponding donor moieties tend to have branched alkyl substituents that sterically hinder interactions with the fullerene. To further explore the idea that the most beneficial polymer:fullerene arrangement involves the fullerene docking with the acceptor moiety, a family of benzo[1,2-b:4,5-b']dithiophene-thieno[3,4-c]pyrrole-4,6-dione polymers (PBDTTPD derivatives) was synthesized and tested in a variety of PV device types with vastly different aggregation states of the polymer. In agreement with our hypothesis, the PBDTTPD derivative with a more sterically accessible acceptor moiety and a more sterically hindered donor moiety shows the highest performance in bulk-heterojunction, bilayer, and low-polymer concentration PV devices where fullerene derivatives serve as the electron-accepting materials. Furthermore, external quantum efficiency measurements of the charge-transfer state and solid-state two-dimensional (2D) (13)C{(1)H} heteronuclear correlation (HETCOR) NMR analyses support that a specific polymer:fullerene arrangement is present for the highest performing PBDTTPD derivative, in which the fullerene is in closer proximity to the acceptor moiety of the polymer. This work demonstrates that the polymer:fullerene arrangement and resulting intermolecular interactions may be key factors in determining the performance of OPV material
Energy Technology Data Exchange (ETDEWEB)
Christensen, Anders S., E-mail: andersx@chem.wisc.edu, E-mail: cui@chem.wisc.edu; Cui, Qiang, E-mail: andersx@chem.wisc.edu, E-mail: cui@chem.wisc.edu [Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, Wisconsin 53706 (United States); Elstner, Marcus [Theoretische Chemische Biologie, Universität Karlsruhe, Kaiserstr. 12, 76131 Karlsruhe (Germany)
2015-08-28
Semi-empirical quantum mechanical methods traditionally expand the electron density in a minimal, valence-only electron basis set. The minimal-basis approximation causes molecular polarization to be underestimated, and hence intermolecular interaction energies are also underestimated, especially for intermolecular interactions involving charged species. In this work, the third-order self-consistent charge density functional tight-binding method (DFTB3) is augmented with an auxiliary response density using the chemical-potential equalization (CPE) method and an empirical dispersion correction (D3). The parameters in the CPE and D3 models are fitted to high-level CCSD(T) reference interaction energies for a broad range of chemical species, as well as dipole moments calculated at the DFT level; the impact of including polarizabilities of molecules in the parameterization is also considered. Parameters for the elements H, C, N, O, and S are presented. The Root Mean Square Deviation (RMSD) interaction energy is improved from 6.07 kcal/mol to 1.49 kcal/mol for interactions with one charged species, whereas the RMSD is improved from 5.60 kcal/mol to 1.73 for a set of 9 salt bridges, compared to uncorrected DFTB3. For large water clusters and complexes that are dominated by dispersion interactions, the already satisfactory performance of the DFTB3-D3 model is retained; polarizabilities of neutral molecules are also notably improved. Overall, the CPE extension of DFTB3-D3 provides a more balanced description of different types of non-covalent interactions than Neglect of Diatomic Differential Overlap type of semi-empirical methods (e.g., PM6-D3H4) and PBE-D3 with modest basis sets.
Sturm, Erica J.
Strong correlation due to multi-referenced electronic states of quantum chemical systems are crucial for a proper understanding of important phenomena including excited states, bond breakage and formation, singlet fission and biological transport. By solving for the 2-electron reduced density matrix (2-RDM) directly via the anti-Hermitian contracted Schrodinger equation (ACSE) we provide a balanced treatment of single and multi-referenced correlation effects without utilizing the N-electron wave function. This significantly reduces the computational expense while still maintaining near full configuration interaction accuracy when available. When provided with an initial 2-RDM guess from an active-space multi-configuration self consistent field wave function the ACSE scales as [special characters omitted] where ra is the number of active molecular orbitals (MOs) and ra is the number of external MOs. This work demonstrates the energetic accuracy of ACSE calculations with several small multi-referenced systems and presents a novel approach for investigating intermolecular interactions, using a simple dimer test case. In this monomer-optimized basis set approach we compute each monomer's properties in isolation and obtain a set of natural orbitals that best describe the monomer. We then remove or truncate orbitals deemed excessive as a function of occupation number, defining a monomer molecular orbital basis uniquely suited to that monomer. Combining two such monomers yields a super-system expressed in the monomer basis which we then rotate to a dimer basis at a desired geometry before creating a new initial 2-RDM for the final optimization by an ACSE calculation. It is found that the intermolecular properties calculated in this fashion from larger atomic basis sets maintain their high accuracy but at a fraction of the computational cost. Furthermore this basis set optimization is free of basis set superposition error, circumventing the need for an expensive
Hobson, Art
2012-01-01
Nonlocality arises from the unified "all or nothing" interactions of a spatially extended field quantum such as a photon or an electron. In the double-slit experiment with light, for example, each photon comes through both slits and arrives at the viewing screen as an extended but unified energy bundle or "field quantum." When the photon interacts…
Hobson, Art
2012-01-01
Nonlocality arises from the unified "all or nothing" interactions of a spatially extended field quantum such as a photon or an electron. In the double-slit experiment with light, for example, each photon comes through both slits and arrives at the viewing screen as an extended but unified energy bundle or "field quantum." When the photon interacts…
Energy Technology Data Exchange (ETDEWEB)
Miranda, Guillermo L. [Fisica Teorica y Aplicada, Escuela de Ingenieria de Antioquia, A.A. 7516, Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque_echeverri@yahoo.es [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia)
2012-10-15
The dependencies of the binding energies of the lowest four 1s-like exciton states in GaAs-(Ga,Al)As coupled double quantum wells (CDQW) on the geometric parameters of the system are theoretically studied. A variational approach, together with the parabolic band and effective mass approximations, were considered in order to perform the numerical calculations. It is shown that in the case of a symmetric system there is a degeneracy between the heavy-hole even and odd states and this degeneracy can be removed by the presence of a sufficiently narrow middle barrier. In contrast to this fact, the electron even and odd states are never degenerated. It is detected that, if the system is asymmetric, there will appear binding energies anticrossings between the heavy-hole states at the point of the asymmetric {yields} symmetric QW transition. - Highlights: Black-Right-Pointing-Pointer Study of 1s-like exciton states in double quantum wells. Black-Right-Pointing-Pointer Binding energy decreases with the presence of second well. Black-Right-Pointing-Pointer Binding energy of (2,2) state can be larger than (1,1) state. Black-Right-Pointing-Pointer Central barrier can remove degeneracy of states. Black-Right-Pointing-Pointer Anticrossing between states can be induced via symmetries.
Quantum transport in carbon nanotubes
DEFF Research Database (Denmark)
Laird, Edward A.; Kuemmeth, Ferdinand; Steele, Gary A.
2015-01-01
. In single quantum dots defined in short lengths of nanotube, the energy levels associated with each degree of freedom, and the spin-orbit coupling between them, are revealed by Coulomb blockade spectroscopy. In double quantum dots, the combination of quantum numbers modifies the selection rules of Pauli...
Kendon, Vivien M; Nemoto, Kae; Munro, William J
2010-08-13
We briefly review what a quantum computer is, what it promises to do for us and why it is so hard to build one. Among the first applications anticipated to bear fruit is the quantum simulation of quantum systems. While most quantum computation is an extension of classical digital computation, quantum simulation differs fundamentally in how the data are encoded in the quantum computer. To perform a quantum simulation, the Hilbert space of the system to be simulated is mapped directly onto the Hilbert space of the (logical) qubits in the quantum computer. This type of direct correspondence is how data are encoded in a classical analogue computer. There is no binary encoding, and increasing precision becomes exponentially costly: an extra bit of precision doubles the size of the computer. This has important consequences for both the precision and error-correction requirements of quantum simulation, and significant open questions remain about its practicality. It also means that the quantum version of analogue computers, continuous-variable quantum computers, becomes an equally efficient architecture for quantum simulation. Lessons from past use of classical analogue computers can help us to build better quantum simulators in future.
Institute of Scientific and Technical Information of China (English)
王素新; 李玉现; 王宁; 刘建军
2016-01-01
Owing to their potential applications in topological quantum computation and because of their fundamental interest, Majorana fermions are currently attracting increasing attention. Numerous theoretical and experimental studies exactly show that the quantum dot (QD) structure is a good candidate for the detection of Majorana bound state (MBSs). QD system has many unique transport properties and interesting quantum phenomena, such as quantum interference effect, Fano effect, etc. In addition, compared with a single QD, a coupled QD structure has many adjustable parameters, and thus has more important theoretical and practical value, which provides an excellent platform to detect MBSs. In addition, QD coupled with normal metallic conductor and with superconducting electrode structure exhibits interesting transport properties. One of these properties is the so-called Andreev reflection (AR). Especially, in the subgap regime, the current almost entirely originates from the anomalous Andreev channel; such spectroscopy can thus directly probe any in-gap state. In the present paper, we consider a T-shaped double QD structure with side-coupled to MBSs and investigate the transport properties through the system by adding a normal and a superconducting lead. We calculate the AR conductance through the system in the subgap transport. Here we focus on the effects of MBSs on AR through the system. We find that the AR conductance presents a resonant peak around zero Fermi energy when only one QD (QD1) connects to metal and superconducting leads. As a consequence of quantum interference, when using another QD2 side-attached to QD1, a pair of new Fano-type resonant peaks appear and is distributed aside the zero point and the Fano antiresonant point is at the energy level of the QD2. If an MBS is introduced to couple to QD2, the AR conductance shows several new features. First, a pair of new Fano-type resonance curves appears and the original ones also persist except for the
Institute of Scientific and Technical Information of China (English)
李娜; 孙捷; 王晓静; 孙敬勇; 王兵
2016-01-01
A double quantum dots nanocomposite of CdSe@ SiO2‐CdTe was synthesized based on the electrostatic adsorption .A Cd‐NO complex was formed by the combination of nitric ox‐ide (NO) with Cd ions on the surface of CdTe quantum dots ,which led to CdTe quantum dots fluorescence quenching , without affecting the fluorescence of CdSe quantum dots .Further‐more ,its utility was carried out to detect NO quantitatively according to the linear relationship between the concentrations of NO (0 1.~2 2. μmol/L) and the relevant I603/I532 values of the ratiometric fluorescent sensor .%通过静电吸附作用，合成了CdSe＠ SiO2‐CdTe双量子点的纳米复合物．一氧化氮（NO）与CdTe量子点表面Cd离子结合形成Cd‐NO复合物，引起CdTe量子点荧光猝灭，而不影响CdSe量子点的荧光．当NO浓度在01．～22．μmol／L之间变化时，该探针荧光强度比值 I603／I532符合线性关系（R＝－09．954），从而实现对NO的定量检测．
Andersen, J.; Heimdal, J.; Mahler, D. W.; Nelander, B.; Larsen, R. Wugt
2014-03-01
Terahertz absorption spectra have been recorded for the weakly bound CO2-H2O complex embedded in cryogenic neon matrices at 2.8 K. The three high-frequency van der Waals vibrational transitions associated with out-of-plane wagging, in-plane rocking, and torsional motion of the isotopic H2O subunit have been assigned and provide crucial observables for benchmark theoretical descriptions of this systems' flat intermolecular potential energy surface. A (semi)-empirical value for the zero-point energy of 273 ± 15 cm-1 from the class of intermolecular van der Waals vibrations is proposed and the combination with high-level quantum chemical calculations provides a value of 726 ± 15 cm-1 for the dissociation energy D0.
Energy Technology Data Exchange (ETDEWEB)
Andersen, J.; Mahler, D. W.; Larsen, R. Wugt, E-mail: rewl@kemi.dtu.dk [Department of Chemistry, Technical University of Denmark, Kemitorvet 206, 2800 Kgs. Lyngby (Denmark); Heimdal, J.; Nelander, B. [MAX-IV Laboratory, Lund University, P. O. Box 118, 22100 Lund (Sweden)
2014-03-07
Terahertz absorption spectra have been recorded for the weakly bound CO{sub 2}–H{sub 2}O complex embedded in cryogenic neon matrices at 2.8 K. The three high-frequency van der Waals vibrational transitions associated with out-of-plane wagging, in-plane rocking, and torsional motion of the isotopic H{sub 2}O subunit have been assigned and provide crucial observables for benchmark theoretical descriptions of this systems’ flat intermolecular potential energy surface. A (semi)-empirical value for the zero-point energy of 273 ± 15 cm{sup −1} from the class of intermolecular van der Waals vibrations is proposed and the combination with high-level quantum chemical calculations provides a value of 726 ± 15 cm{sup −1} for the dissociation energy D{sub 0}.
Intermolecular and intramolecular electron transfer from eosin ester to viologen
Institute of Scientific and Technical Information of China (English)
张丰雷; 张曼华; 沈涛
1996-01-01
The covalently -(CH2)10- linked eosin-butylviologen compound has been synthesized. The photoinduced electron transfer of eosin ester and butylviologen as well as the influence of addition of cyclodextrin or amylose into the solution of linked compound on the system have been studied by the absorption spectra, fluorescence spectra and fluorescence lifetime. The results indicated that the intramolecular electron transfer is much more efficient than the intermolecular one. Due to the formation of inclusion complex, the process of intramolecular electron transfer was changed after adding cydodextrin or amylose.
An approach to the intermolecular energy in pure liquids
Directory of Open Access Journals (Sweden)
GAbriel Hernández de la Torre
2010-07-01
Full Text Available Se propone un método para: estimar la energía potencial de repulsión de cualquier molécula central como una función de las densidades ortobáricas en líquidos puros no auto asociados; estimar los parámetros necesarios para calcular la energía de dispersión de London; calcular los números de coordinación promedio, distancias intermoleculares de interacción, diámetros moleculares y de grupos; en moléculas globulares, moléculas planas y parafinas normales.
Effects of intermolecular interaction on inelastic electron tunneling spectra
Kula, Mathias; Luo, Yi
2008-02-01
We have examined the effects of intermolecular interactions on the inelastic electron tunneling spectroscopy (IETS) of model systems: a pair of benzenethiol or a pair of benzenedithiol sandwiched between gold electrodes. The dependence of the IETS on the mutual position of and distance between the paired molecules has been predicted and discussed in detailed. It is shown that, although in most cases, there are clear spectral fingerprints present which allow identification of the actual structures of the molecules inside the junction. Caution must be exercised since some characteristic lines can disappear at certain symmetries. The importance of theoretical simulation is emphasized.
Anisotropic Compression. What can it Teach us About Intermolecular Interactions?
Boldyreva, Elena
The effect of pressure on solids is often discussed in terms of bulk compressibility. At the same time, for any solids with the crystal structures, the symmetry of which is lower than cubic, it is not sufficient to describe the bulk compressibility alone, since the structural distortion is anisotropic - i.e. depends on the crystallographic direction. The lecture gives a comprehensive introduction into the techniques of studying the strain anisotropy based on diffraction experiments, and illustrates, how the knowledge of the anisotropy of lattice strain may assist in understanding the intermolecular interactions in crystals.
INTERMOLECULAR FORCES IN ASSOCIATION OF PURINES WITH POLYBENZENOID HYDROCARBONS.
PULLMAN, B; CLAVERIE, P; CAILLET, J
1965-03-12
The interactions in solution between purine or pyrimidine bases and polybenzenoid aromatic hydrocarbons probably consist in a vertical, stacking-type physical association. By molecular orbital calculations the role of the Van der Waals-London intermolecular forces in these interactions is determined. The electrostatic dipole-dipole forces are negligible, the polarization (or induction) dipole-induced dipole forces are contributory, but most important are the dispersion (or fluctuation) forces. This loose, physical type of interaction should not show any specificity with respect to the carcinogenic activity of the hydrocarbons.
Towards the biaxial nematic phase via specific intermolecular interactions
Omnes, L
2001-01-01
The work described in this thesis has been focussed on the search of an elusive liquid crystal phase, known as the biaxial nematic phase. Indeed, despite nearly thirty years of intense research, no-one has been able to characterise unambiguously a biaxial nematic phase in a low-molar-mass thermotropic system. Our research is based on the concept of molecular biaxiality as distinct from shape biaxiality. Thus, we are seeking to design palladium complexes where specific intermolecular interactions could exist. Therefore, a few original synthetic strategies were developed to tackle the challenge of discovering the biaxial nematic phase
Duality Computing in Quantum Computers
Institute of Scientific and Technical Information of China (English)
LONG Gui-Lu; LIU Yang
2008-01-01
In this letter, we propose a duality computing mode, which resembles particle-wave duality property when a quantum system such as a quantum computer passes through a double-slit. In this mode, computing operations are not necessarily unitary. The duality mode provides a natural link between classical computing and quantum computing. In addition, the duality mode provides a new tool for quantum algorithm design.
Many worlds interpretation for double slit experiment
Yun, Zinkoo
2014-01-01
As is well known, the double slit experiment contains every key concepts of quantum mechanics such as phase effect, probability wave, quantum interference, quantum superposition. In this article, I will clarify the meaning of quantum superposition in terms of phase effect between states. After applying standard quantum theory, it leads to serious questions about the unitary process of an isolated system. It implies that non collapsing interpretations including many worlds may not be justified. This also could explain that there is no such boundary between classical and quantum domains.
Quantitative analysis of intermolecular interactions in orthorhombic rubrene
Directory of Open Access Journals (Sweden)
Venkatesha R. Hathwar
2015-09-01
Full Text Available Rubrene is one of the most studied organic semiconductors to date due to its high charge carrier mobility which makes it a potentially applicable compound in modern electronic devices. Previous electronic device characterizations and first principles theoretical calculations assigned the semiconducting properties of rubrene to the presence of a large overlap of the extended π-conjugated core between molecules. We present here the electron density distribution in rubrene at 20 K and at 100 K obtained using a combination of high-resolution X-ray and neutron diffraction data. The topology of the electron density and energies of intermolecular interactions are studied quantitatively. Specifically, the presence of Cπ...Cπ interactions between neighbouring tetracene backbones of the rubrene molecules is experimentally confirmed from a topological analysis of the electron density, Non-Covalent Interaction (NCI analysis and the calculated interaction energy of molecular dimers. A significant contribution to the lattice energy of the crystal is provided by H—H interactions. The electron density features of H—H bonding, and the interaction energy of molecular dimers connected by H—H interaction clearly demonstrate an importance of these weak interactions in the stabilization of the crystal structure. The quantitative nature of the intermolecular interactions is virtually unchanged between 20 K and 100 K suggesting that any changes in carrier transport at these low temperatures would have a different origin. The obtained experimental results are further supported by theoretical calculations.
Intermolecular interactions and the thermodynamic properties of supercritical fluids.
Yigzawe, Tesfaye M; Sadus, Richard J
2013-05-21
The role of different contributions to intermolecular interactions on the thermodynamic properties of supercritical fluids is investigated. Molecular dynamics simulation results are reported for the energy, pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound of fluids interacting via both the Lennard-Jones and Weeks-Chandler-Andersen potentials. These properties were obtained for a wide range of temperatures, pressures, and densities. For each thermodynamic property, an excess value is determined to distinguish between attraction and repulsion. It is found that the contributions of intermolecular interactions have varying effects depending on the thermodynamic property. The maxima exhibited by the isochoric and isobaric heat capacities, isothermal compressibilities, and thermal expansion coefficient are attributed to interactions in the Lennard-Jones well. Repulsion is required to obtain physically realistic speeds of sound and both repulsion and attraction are necessary to observe a Joule-Thomson inversion curve. Significantly, both maxima and minima are observed for the isobaric and isochoric heat capacities of the supercritical Lennard-Jones fluid. It is postulated that the loci of these maxima and minima converge to a common point via the same power law relationship as the phase coexistence curve with an exponent of β = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids.
Jaffe, Arthur
2016-01-01
Here we introduce reflection positive doubles, a general framework for reflection positivity, covering a wide variety of systems in statistical physics and quantum field theory. These systems may be bosonic, fermionic, or parafermionic in nature. Within the framework of reflection positive doubles, we give necessary and sufficient conditions for reflection positivity. We use a reflection-invariant cone to implement our construction. Our characterization allows for a direct interpretation in terms of coupling constants, making it easy to check in concrete situations. We illustrate our methods with numerous examples.
Institute of Scientific and Technical Information of China (English)
BAI Yu-Lin; CHENG Xiao-Hong; CHEN Xiang-Rong; YANG Xiang-Dong; ZHU Jun
2004-01-01
@@ The intermolecular interactions potentials for two configurations of CH4-Ne complex are calculated with local density approximation methods in the frame of density functional theory. It is found that the calculated potentials have two minima when the distance between the carbon atom of CH4 and the Ne atom takes R = 5.80 a.u.and 6.20a. u. for both the two configurations. For the edge configuration, the corresponding depth of the potential is 0.0669536 eV and 0.0671416 eV. For the face configuration, the corresponding depth of the potential is 0.0737956 eV and 0.0645506 eV. The global minimum occurs at R = 5.80 a.u. for the face configuration with a depth of the potential 0.0737956 eV. The depths of our calculation are in better agreement with the experimental data than the quantum chemical calculation approach, while the position of minimum potential for our calculation is underestimated.
Directory of Open Access Journals (Sweden)
Sounak Sarkar
2017-01-01
Full Text Available Octachloronaphthalene (OCN, a serious environmental pollutant, has been investigated by charge density analysis to unravel several unexplored factors responsible for steric overcrowding. The topological features of the enigmatic peri interactions contributing to steric overcrowding are qualified and quantified from experimental and theoretical charge-density studies. A new facet in the fundamental understanding of peri interactions is revealed by NCI (non-covalent interaction analysis. The potential role of these interactions in deforming the molecular geometry and subsequent effect on aromaticity are substantiated from NICS (Nuclear Independent Chemical Shift and QTAIM (Quantum Theory of Atoms in Molecules calculations. The eye-catching dissimilarity in the out-of-plane twisting of OCN renders the molecule in an asymmetric geometry in the crystalline phase compared with symmetric geometry in the optimized solvated phase. This is uniquely characterized by their molecular electrostatic potential (MESP, respectively, and is explained in terms of conflict between two opposing forces – peri interactions, and symbiotic intermolecular Cl...Cl and Cl...π contacts.
Sarkar, Sounak; Row, Tayur N Guru
2017-01-01
Octachloronaphthalene (OCN), a serious environmental pollutant, has been investigated by charge density analysis to unravel several unexplored factors responsible for steric overcrowding. The topological features of the enigmatic peri interactions contributing to steric overcrowding are qualified and quantified from experimental and theoretical charge-density studies. A new facet in the fundamental understanding of peri interactions is revealed by NCI (non-covalent interaction) analysis. The potential role of these interactions in deforming the molecular geometry and subsequent effect on aromaticity are substantiated from NICS (Nuclear Independent Chemical Shift) and QTAIM (Quantum Theory of Atoms in Molecules) calculations. The eye-catching dissimilarity in the out-of-plane twisting of OCN renders the molecule in an asymmetric geometry in the crystalline phase compared with symmetric geometry in the optimized solvated phase. This is uniquely characterized by their molecular electrostatic potential (MESP), respectively, and is explained in terms of conflict between two opposing forces - peri interactions, and symbiotic intermolecular Cl⋯Cl and Cl⋯π contacts.
Chemical Dynamics Simulations of Intermolecular Energy Transfer: Azulene + N2 Collisions.
Kim, Hyunsik; Paul, Amit K; Pratihar, Subha; Hase, William L
2016-07-14
Chemical dynamics simulations were performed to investigate collisional energy transfer from highly vibrationally excited azulene (Az*) in a N2 bath. The intermolecular potential between Az and N2, used for the simulations, was determined from MP2/6-31+G* ab initio calculations. Az* is prepared with an 87.5 kcal/mol excitation energy by using quantum microcanonical sampling, including its 95.7 kcal/mol zero-point energy. The average energy of Az* versus time, obtained from the simulations, shows different rates of Az* deactivation depending on the N2 bath density. Using the N2 bath density and Lennard-Jones collision number, the average energy transfer per collision ⟨ΔEc⟩ was obtained for Az* as it is collisionally relaxed. By comparing ⟨ΔEc⟩ versus the bath density, the single collision limiting density was found for energy transfer. The resulting ⟨ΔEc⟩, for an 87.5 kcal/mol excitation energy, is 0.30 ± 0.01 and 0.32 ± 0.01 kcal/mol for harmonic and anharmonic Az potentials, respectively. For comparison, the experimental value is 0.57 ± 0.11 kcal/mol. During Az* relaxation there is no appreciable energy transfer to Az translation and rotation, and the energy transfer is to the N2 bath.
Luo, Shuai; Ji, Hai-Ming; Yang, Xiao-Guang; Yang, Tao
2013-07-01
The impact of a double-cap procedure using two growth temperatures on the optical characteristics of InAs/InGaAsP/InP quantum dots (QDs) grown by metal-organic chemical vapor deposition has been investigated. With a combination of optimized thickness of the first cap layer and elevated growth temperature for the second cap layer, it is found that the photoluminescence (PL) linewidth of QDs can be significantly reduced from 124 meV to 87 meV at room temperature (RT). This reduction in PL linewidth is likely to be due to the enhanced As/P exchange reaction and indium migration at high growth temperature, which lead to a more uniform QD height distribution. Moreover, the uniformity of the PL peak intensity and peak energy on the wafer surface is evidently improved due to the higher material quality achieved when an elevated temperature is used for the SCL growth.
DEFF Research Database (Denmark)
Pedersen, Jesper Goor; Zhang, Lei; Gilbert, M.J.
2010-01-01
We explore exchange coupling of a pair of spins in a double dot and in an optical lattice, using the frequency of exchanges in a bosonic path integral, evaluated using Monte Carlo simulation. The algorithm gives insights into the role of correlation through visualization of two-particle probability...
Institute of Scientific and Technical Information of China (English)
缪中林; 陈平平; 蔡炜颖; 李志锋; 袁先漳; 刘平; 史国良; 徐文兰; 陆卫; 陈昌明; 朱德彰; 潘浩昌; 胡军; 李明乾
2001-01-01
用分子束外延系统(MBE)生长了GaAs/AlGaAs不对称耦合双量子阱(ACDQW)，采用组合注入质子的方法，在同一块衬底上获得了不同注入剂量的GaAs/AlGaAs不对称耦合双量子阱单元，没有经过快速热退火的过程，在常温下测量了不同注入剂量量子阱单元的显微光荧光谱和光调制反射光谱，发现了各区域子带间跃迁能量最大变化范围达到81meV.由于样品未作高温热退火处理，为此由Al组分误差函数模型推导的扩散长度要大大高于扩散系数公式.耦合量子阱的界面混合效应对于质子注入非常敏感.%With combinatorial proton implantation, we obtained several areas with different implantation doses in single wafer of GaAs/AlGaAs asymmetry coupling double quantum well grown by MBE, and studied the optical characteristics with photoluminescence (PL) and photo-modulated reflectance(PR). Without rapid thermal annealing, maximum transition energy shift 81 meV was obtained in single wafer. The diffusion lengths of Al component calculated from error function were larger than that calculated from coefficient of diffusion formula. The interface effect of double quantum well is sensitive to proton implantation.
Energy Technology Data Exchange (ETDEWEB)
Baghramyan, H.M.; Barseghyan, M.G.; Kirakosyan, A.A. [Department of Solid State Physics, Yerevan State University, Al. Manookian 1, 0025 Yerevan (Armenia); Restrepo, R.L. [Física Teórica y Aplicada, Escuela de Ingeniería de Antioquia, AA 7516, Medellín (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultadde Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21,Medellín (Colombia); Mora-Ramos, M.E. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultadde Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21,Medellín (Colombia); Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultadde Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21,Medellín (Colombia)
2014-01-15
The linear and nonlinear optical absorption associated with the transition between 1s and 2s states corresponding to the electron-donor-impurity complex in GaAs/Ga{sub 1−x}Al{sub x}As three-dimensional concentric double quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and the variation of the aluminum concentration, the energies of the ground and first excited s-like states of a donor impurity in such a system have been calculated using the effective mass approximation and a variational method. The energies of these states and the corresponding threshold energy of the optical transitions are examined as functions of hydrostatic pressure, aluminum concentration, radial impurity position, as well as the geometrical dimensions of the structure. The dependencies of the linear, nonlinear and total optical absorption coefficients as functions of the incident photon energy are investigated for different values of those mentioned parameters. It is found that the influences mentioned above lead to either redshifts or blueshifts of the resonant peaks of the optical absorption spectrum. It is particularly discussed the unusual property exhibited by the third-order nonlinear of becoming positive for photon energies below the resonant transition one. It is shown that this phenomenon is associated with the particular features of the system under study, which determine the values of the electric dipole moment matrix elements. -- Highlights: • Intra-band optical absorption associated to impurity states in double quantum rings. • Combined effects of hydrostatic pressure and aluminum concentration are studied. • The influences mentioned above lead to shifts of resonant peaks. • It is discussed an unusual property exhibited by the third-order nonlinear absorption.
Lee, Jaehoon; Wilczek, Frank
2013-11-27
Motivated by the problem of identifying Majorana mode operators at junctions, we analyze a basic algebraic structure leading to a doubled spectrum. For general (nonlinear) interactions the emergent mode creation operator is highly nonlinear in the original effective mode operators, and therefore also in the underlying electron creation and destruction operators. This phenomenon could open up new possibilities for controlled dynamical manipulation of the modes. We briefly compare and contrast related issues in the Pfaffian quantum Hall state.
Shumilov, A. A.; Vinnichenko, M. Ya; Balagula, R. M.; Vorobjev, L. E.; Firsov, D. A.; Kulagina, M. M.; Vasil'iev, A. P.; Duque, C. A.; Tiutiunnyk, A.; Akimov, V.; Restrepo, R. L.; Tulupenko, V. N.; Ter-Martirosyan, A. L.
2015-11-01
Modulation of refraction index under transverse electric field was studied in structures with multiple tunnel-coupled GaAs/AlGaAs quantum wells in the spectral range corresponding to intersubband light absorption. The change of refraction index in electric field was calculated using Kramers-Kronig relation and experimentally determined spectra of intersubband light absorption in equilibrium conditions and under transverse electric field.
改进的双链量子遗传算法在图像去噪中的应用%Improved quantum genetic algorithm with double chains in image denoising
Institute of Scientific and Technical Information of China (English)
国强; 孙宇枭
2016-01-01
针对传统双链量子遗传算法收敛速度慢、搜索精度低、鲁棒性差等不足，提出一种F型双链量子遗传算法（ F＿DCQ⁃GA）。对编码空间进行单值映射处理，在保证量子种群适应度值与相应幅角排序单调性的前提下，缩小算法的搜索空间，增加搜索密度；在量子更新时引入自适应步长因子，使步长随目标函数在搜索点处梯度的变化而变化，有效解决了传统寻优算法普遍存在的全局最优解搜索困难的问题；在染色体变异更新时提出了π／6门，克服了原来非门变异无法更新量子比特概率幅的缺点。将F＿DCQGA优化算法应用于小波阈值去噪的阈值选择机制中，通过仿真证明F＿DCQGA优化算法提高了小波阈值函数的收敛速度和搜索精度，在图像边缘特征提取中可以获得更小的均方误差（ SME ）和更大的峰值信噪比（ RPSN ），同时又保留了大部分高频信息。%To solve the problems of slow convergence speed, low search precision and poor robustness in traditional double chains quantum genetic algorithm, a new double chains quantum genetic algorithm ( F_DCQGA ) is proposed. The coding space is mapped to reduce the algorithm searching space and increases searching density, under the premise of guaranteeing quantum population adaptation and argument population monotonicity. The adaptive step⁃length factor is introduced to the quantum updating, which changes the step⁃length with gradient of objective function in searching points. This could solve the global optimal solution search difficulties caused by oscillatory occurrence in traditional optimization algorithm. Quantumπ/6 gate is presented in chromosome mutation upadating, to overcome the shortcoming that NOT gate can not update quantum bit probability amplitude. The F_DCQGA is applied to the threshold selection of wavelet threshold denoising. Simulation results show that F_DCQGA improves the
Quantum cluster algebra structures on quantum nilpotent algebras
Goodearl, K R
2017-01-01
All algebras in a very large, axiomatically defined class of quantum nilpotent algebras are proved to possess quantum cluster algebra structures under mild conditions. Furthermore, it is shown that these quantum cluster algebras always equal the corresponding upper quantum cluster algebras. Previous approaches to these problems for the construction of (quantum) cluster algebra structures on (quantized) coordinate rings arising in Lie theory were done on a case by case basis relying on the combinatorics of each concrete family. The results of the paper have a broad range of applications to these problems, including the construction of quantum cluster algebra structures on quantum unipotent groups and quantum double Bruhat cells (the Berenstein-Zelevinsky conjecture), and treat these problems from a unified perspective. All such applications also establish equality between the constructed quantum cluster algebras and their upper counterparts.
Institute of Scientific and Technical Information of China (English)
贺智明; 梁云飞
2013-01-01
多约束QoS组播路由问题是NP完全问题.提出一种基于双链量子遗传算法的多约束QoS组播路由算法,该算法具有种群多样性、收敛速度快、并行性更高等优点,并对算法具体流程和实现方法进行了详细的描述.实验结果表明,与已有的遗传算法、量子遗传算法相比,该算法有搜索速度快、全局寻优能力强等优点.%Multi-constrained quality-of-service (QoS) routing is an NP complete problem. In this paper we propose a multi-constrained QoS multicast routing algorithm which is based on double chains quantum genetic algorithm ( DCQGA) , the algorithm has the advantages of population diversity, fast convergence speed and better parallelism, etc. We also provide detailed description on specific processes and the implementation means of the algorithm. Experimental results show that compared with existing genetic algorithm and quantum generic algorithm, the proposed algorithm has the advantages of higher search speed and strong global optimisation ability.
Energy Technology Data Exchange (ETDEWEB)
Baghramyan, H.M. [Department of Solid State Physics, Yerevan State University, Al. Manookian 1, 0025 Yerevan (Armenia); Barseghyan, M.G., E-mail: mbarsegh@ysu.am [Department of Solid State Physics, Yerevan State University, Al. Manookian 1, 0025 Yerevan (Armenia); Kirakosyan, A.A. [Department of Solid State Physics, Yerevan State University, Al. Manookian 1, 0025 Yerevan (Armenia); Restrepo, R.L. [Escuela de Ingenieria de Antioquia, AA 7516 Medellin (Colombia); Duque, C.A. [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)
2013-02-15
The linear and nonlinear intra-band optical absorption coefficients in GaAs/Ga{sub 1-x}Al{sub x}As two-dimensional concentric double quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and aluminum concentration the energies of the ground (n=1,l=0) and the first excited state (n=2,l=1) have been found using the effective mass approximation and the transfer matrix formalism. The energies of these states and the corresponding threshold energy of the intra-band optical transitions are examined as a function of hydrostatic pressure and aluminum concentration for different sizes of the structure. We also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as functions of the incident photon energy for different values of hydrostatic pressure, aluminum concentration, sizes of the structure, and incident optical intensity. Its is found that the effects of the hydrostatic pressure and the aluminum concentration lead to a shifting of the resonant peaks of the intra-band optical spectrum. - Highlights: Black-Right-Pointing-Pointer Linear and nonlinear intra-band absorption in quantum rings. Black-Right-Pointing-Pointer Threshold energy strongly depends on the hydrostatic pressure. Black-Right-Pointing-Pointer Threshold energy strongly depends on the stoichiometry and sizes of structure. Black-Right-Pointing-Pointer Optical absorption is affected by the incident optical intensity.
Mesoscopic Cavity Quantum Electrodynamics with Quantum Dots
Childress, L I; Lukin, M D
2003-01-01
We describe an electrodynamic mechanism for coherent, quantum mechanical coupling between spacially separated quantum dots on a microchip. The technique is based on capacitive interactions between the electron charge and a superconducting transmission line resonator, and is closely related to atomic cavity quantum electrodynamics. We investigate several potential applications of this technique which have varying degrees of complexity. In particular, we demonstrate that this mechanism allows design and investigation of an on-chip double-dot microscopic maser. Moreover, the interaction may be extended to couple spatially separated electron spin states while only virtually populating fast-decaying superpositions of charge states. This represents an effective, controllable long-range interaction, which may facilitate implementation of quantum information processing with electron spin qubits and potentially allow coupling to other quantum systems such as atomic or superconducting qubits.
Ashmead, John
2010-01-01
Normally we quantize along the space dimensions but treat time classically. But from relativity we expect a high level of symmetry between time and space. What happens if we quantize time using the same rules we use to quantize space? To do this, we generalize the paths in the Feynman path integral to include paths that vary in time as well as in space. We use Morlet wavelet decomposition to ensure convergence and normalization of the path integrals. We derive the Schr\\"odinger equation in four dimensions from the short time limit of the path integral expression. We verify that we recover standard quantum theory in the non-relativistic, semi-classical, and long time limits. Quantum time is an experiment factory: most foundational experiments in quantum mechanics can be modified in a way that makes them tests of quantum time. We look at single and double slits in time, scattering by time-varying electric and magnetic fields, and the Aharonov-Bohm effect in time.
Cohen, R. E.; Lin, Y.
2015-12-01
We have performed quantum Monte Carlo (QMC) simulations and density functional theory calculations to study the equations of state and phase transitions in (Mg,Fe)SiO3 perovskite (Pv, bridgmanite) and post-perovskite (PPv) .[1] The ground-state energies were derived using quantum QMC simulations and the temperature-dependent Helmholtz free energies were calculated within the quasiharmonic approximation and density functional perturbation theory. Quantum Monte Carlo (QMC) within Diffusion Monte Carlo (DMC) is a stochastic numerical solution of Schrödinger's equation within the fixed many-particle nodes obtained, in our case, from a determinant of DFT orbitals. Agreement with experiments is improved over DFT alone. Furthermore, we obtain statistical error bounds on the results, rather than the unconstrained errors of DFT. The Pv-PPv phase boundary calculated from our QMC equations of state is also consistent with experiments, and better than previous DFT computations. In order to understand the H-phase reported in (Mg,Fe)SiO3 [2], we have performed evolutionary structure searching for FeSiO3.[3] We find a new structure type which may be consistent with the experimental observations, but is a lower pressure, less dense, phase. We have built a thermodynamic model for (Mg,Fe)SiO3 perovskite as a function of P and T, and will discuss implications for the location of the phase boundary in D'' and its double crossing [4]. This work is supported by NSF and the ERC Advanced Grant ToMCaT. [1] Y. Lin, R. E. Cohen, S. Stackhouse, K. P. Driver, B. Militzer, L. Shulenburger, and J. Kim, Phys. Rev. B 90 (2014). [2] L. Zhang et al., Science 344, 877 (2014). [3] R. E. Cohen and Y. Lin, Phys. Rev. B 90 (2014). [4] J.W. Hernlund, C. Thomas and P.J. Tackley, Nature 434, 882 (2005).
Ab initio intermolecular potential energy surfaces for the Ar-NCCN van der Waals complexes
Solimannejad, Mohammad; Jouypazadeh, Hamidreza; Farrokhpour, Hossein
2014-11-01
The intermolecular potential energy surface of complex pairing argon with cyanogen molecule (NCCN) was calculated using the coupled cluster with single and double and perturbative triple excitations (CCSD(T)) with aug-cc-pvdz basis set extended with a set of mid-bond (3s3p2d1f1g) functions. The interaction energies were calculated by the supermolecular approach with the full counterpoise correction for the basis set superposition error. The calculated potential energies were fitted to an analytical expression. The calculated Ar-NCCN potential energy surface shows a global minimum at 3.35 Å, the distance between argon and centre of mass of cyanogen, for the T-shaped geometry and two local minimum at distance of 5.54 Å for the linear geometry on one side of cyanogen. Finally, the interaction second virial coefficients were calculated using the fitted potential energy surface and were compared with those obtained by the parameters of the Beattie-Bridgeman equation of states of pure argon and cyanogens fluids, approximately.
An ab initio Study of Intermolecular Pontential for Ne—HBr Complex
Institute of Scientific and Technical Information of China (English)
张愚; 史鸿运
2002-01-01
The potential energy surface of the ground state of the Ne-HBr complex has been calculated at several levels of the ory,in cluding the single and double excitation coupled-cluster method with noniterative perturbation treatment of triple excitation CCSD(T),Calculations have been performed using the augmented corredlation-consistent polarized quadruple zeta basis set (aug-cc-pVQAZ).Using the complete basis set (SBS),the global minimum with a well depth of approximate 70.516 cm-1 has been found for the linear Ne-Br-H structure (θ=180.0°） with the distance between the Ne atom and the center of mass of the HF molecule equals (0.351nm)，In addition to the global minimum ,there in a secondary minimum at Rm=0.410 nm and θ＝0° (a well depth of 57.898 cm-1),At last,the effects of the basis sets ,H-Br bond length and theoretical methods on the intermolecular potential calculations of such weakly bound van der Waals complexes were discussed.
An ab initio Study of Intermolecular Potential for Ne-HBr Complex
Institute of Scientific and Technical Information of China (English)
ZHANG,Yu(张愚); SHI,Hong-Yun(史鸿运)
2002-01-01
The potential energy surface of the ground state of the NeHBr complex has been calculated at several levels of theory, including the single and double excitation coupled-cluster method with noniterative perturbation treatment of triple excitation CCSD(T). Calculations have been performed ussing the augmented correlation-consistent polarized quadruple zeta basis set (aug-cc-pVQZ). Using the complete basis set (CBS), the global minimum with a well depth of approximate 70.516 cm- 1 has been found for the linear Ne-Br-H structure (θ =180.0°) with the distance between the Ne atom and the center of mass of the HF molecule equals (0.351 nm). In addition to the global minimum, there is a secondary minimum at Rm =0.410 nm and θ = 0° (a well depth of 57.898 cm-1). At last,the effects of the basis sets, H-Br bond length and theoretical methods on the intermolecular potential calculations of such weakly bound van der Waals complexes were discussed.
Intermolecular Interactions in the TMEM16A Dimer Controlling Channel Activity
Scudieri, Paolo; Musante, Ilaria; Gianotti, Ambra; Moran, Oscar; Galietta, Luis J. V.
2016-12-01
TMEM16A and TMEM16B are plasma membrane proteins with Ca2+-dependent Cl- channel function. By replacing the carboxy-terminus of TMEM16A with the equivalent region of TMEM16B, we obtained channels with potentiation of channel activity. Progressive shortening of the chimeric region restricted the “activating domain” to a short sequence close to the last transmembrane domain and led to TMEM16A channels with high activity at very low intracellular Ca2+ concentrations. To elucidate the molecular mechanism underlying this effect, we carried out experiments based on double chimeras, Forster resonance energy transfer, and intermolecular cross-linking. We also modeled TMEM16A structure using the Nectria haematococca TMEM16 protein as template. Our results indicate that the enhanced activity in chimeric channels is due to altered interaction between the carboxy-terminus and the first intracellular loop in the TMEM16A homo-dimer. Mimicking this perturbation with a small molecule could be the basis for a pharmacological stimulation of TMEM16A-dependent Cl- transport.
Cogan, Uri; Shpigelman, Avi; Portnaya, Irina; Rutenberg, Abraham; Scolnik, Yosef; Shinitzky, Meir
2012-07-01
Supramolecular chiral assemblies of R(-) and S(+) 2-butanol, in their neat form or when dissolved in their nonchiral isomer isobutanol, were evaluated by isothermal titration calorimetry (ITC) ensuing mixing. Dilution of 0.5 M solution of R(-) 2-butanol in isobutanol into the latter liberated heat of several calories per mole, which was approximately double than that obtained in parallel dilutions of S(+) 2-butanol in isobutanol. The ITC dilution profiles indicated an estimate of about 100 isobutanol solvent molecules surrounding each of the 2-butanol enantiomers, presumably arranged in chiral configurations, with different adopted order between the isomers. Mixings of neat R and S 2-butanol were followed by endothermic ITC profiles, indicating that, in racemic 2-butanol, both the supramolecular order and the intermolecular binding energies are lower than in each of the neat chiral isomers. The diversion from symmetrical ITC patterns in these mixings indicated again a subtle difference in molecular organization between the neat enantiomers. It should be noted that the presence of impurities, α-pinene and teterhydrofuran, at a level totaling 0.5%, did not influence the ITC heat flow profiles. The findings of this study demonstrate for the first time that chiral solutes in organic solvents are expected to acquire asymmetric solvent envelopes that may be different between the enantiomers, thus broadening this phenomenon beyond the previously demonstrated cases in aqueous solutions.
Ground state analytical ab initio intermolecular potential for the Cl{sub 2}-water system
Energy Technology Data Exchange (ETDEWEB)
Hormain, Laureline; Monnerville, Maurice, E-mail: maurice.monnerville@univ-lille1.fr; Toubin, Céline; Duflot, Denis; Pouilly, Brigitte; Briquez, Stéphane [Laboratoire de Physique des Lasers Atomes et Molécules, Unité Mixte de Recherche (UMR) 8523, Université Lille I, Bât. P5, 59655 Villeneuve d’Ascq Cedex (France); Bernal-Uruchurtu, Margarita I.; Hernández-Lamoneda, Ramón [Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Cuernavaca 62209, México (Mexico)
2015-04-14
The chlorine/water interface is of crucial importance in the context of atmospheric chemistry. Modeling the structure and dynamics at this interface requires an accurate description of the interaction potential energy surfaces. We propose here an analytical intermolecular potential that reproduces the interaction between the Cl{sub 2} molecule and a water molecule. Our functional form is fitted to a set of high level ab initio data using the coupled-cluster single double (triple)/aug-cc-p-VTZ level of electronic structure theory for the Cl{sub 2} − H{sub 2}O complex. The potential fitted to reproduce the three minima structures of 1:1 complex is validated by the comparison of ab initio results of Cl{sub 2} interacting with an increasing number of water molecules. Finally, the model potential is used to study the physisorption of Cl{sub 2} on a perfectly ordered hexagonal ice slab. The calculated adsorption energy, in the range 0.27 eV, shows a good agreement with previous experimental results.
Intermolecular-charge-transfer-induced fluorescence quenching in protic solvent
Lin, Tao; Liu, Xiaojun; Lou, Zhidong; Hou, Yanbing; Teng, Feng
2016-11-01
The fluorescence quenching of fluorenone in protic solvent has been extensively investigated, and the intermolecular hydrogen bond was found to play a crucial role. Unfortunately, the mechanism at atomic level is still not clear. In the present work, we theoretically put forward the charge transfer along the hydrogen bond in the excited states. The vertical excitation energies of the fluorenone-methanol complex as well as the potential energy profiles and surfaces of the vertical excited states and charge transfer states were calculated by using the ab initio electronic-structure methods. The photochemical reactions occurring in the diverse charge transfer states were compared and their decisiveness to the fluorescence quenching was discussed in the paper.
INTERMOLECULAR AND INTRAMOLECULAR INTERACTIONS OF POLYMER GUAR GUM IN SOLUTIONS
Institute of Scientific and Technical Information of China (English)
Yun-fei Yan; Hai-yang Yang; Wen-yong Liu; Ping-ping Zhu; Ping-sheng He
2005-01-01
The tetrahedral borate ion can crosslink with polymer guar gum in aqueous solutions. If the concentration of guar gum is less than 0.045 g/dL, the intramolecular interaction between guar gum and borate ion increases due to the formation of crosslinks. As a result, the polymer chains of guar gum in solution shrink in size and the reduced viscosity of polymer solution decreases accordingly. On the other hand, if the concentration of guar gum is greater than 0.045 g/dL, the intermolecular interaction becomes apparent due to the same reason. The polymer chains, therefore, associate together and the reduced viscosity of polymer solution increases considerably. According to this technique, the critical concentration c*,presented by de-Gennes[1], is determined successfully.
Nano-spectroscopic imaging of intermolecular structure, coupling and dynamics
Pollard, Benjamin; Hinrichs, Karsten; Raschke, Markus B
2013-01-01
Molecular self-assembly, the function of biomembranes, and the performance of organic solar cells rely on molecular interactions on the nanoscale. The understanding and design of such intrinsic or engineered heterogeneous functional soft matter has long been impeded by a lack of spectroscopic tools with sufficient nanometer spatial resolution, attomolar sensitivity, and intermolecular spectroscopic specificity. We implement vibrational scattering-scanning near-field optical microscopy ($s$-SNOM) in a multi-spectral modality with unprecedented spectral precision to investigate the structure-function relationship in nano-phase separated block-copolymers. We use a vibrational resonance as a sensitive reporter of the local chemical environment and resolve, with few nanometer spatial resolution and 0.2 cm$^{-1}$ spectral precision, spectral Stark shifts and line broadening correlated with molecular-scale morphologies. By creating images of solvatochromic vibrational shifts we discriminate local variations in elect...
Thermodynamic curvature for attractive and repulsive intermolecular forces.
May, Helge-Otmar; Mausbach, Peter; Ruppeiner, George
2013-09-01
The thermodynamic curvature scalar R for the Lennard-Jones system is evaluated in phase space, including vapor, liquid, and solid state. We paid special attention to the investigation of R along vapor-liquid, liquid-solid, and vapor-solid equilibria. Because R is a measure of interaction strength, we traced out the line R=0 dividing the phase space into regions with effectively attractive (R0) interactions. Furthermore, we analyzed the dependence of R on the strength of attraction applying a perturbation ansatz proposed by Weeks-Chandler-Anderson. Our results show clearly a transition from R>0 (for poorly repulsive interaction) to R<0 when loading attraction in the intermolecular potential.
Weak intermolecular interactions in gas-phase NMR
Garbacz, Piotr; Jackowski, Karol; Moszynski, Robert; Jaszunski, Michal
2011-01-01
Gas-phase NMR spectra demonstrating the effect of weak intermolecular forces on the NMR shielding constants of the interacting species are reported. We analyse the interaction of the molecular hydrogen isotopomers with He, Ne, and Ar, and the interaction in the He-CO_2 dimer. The same effects are studied for all these systems in the ab initio calculations. The comparison of the experimental and computed shielding constants is shown to depend strongly on the treatment of the bulk susceptibility effects, which determine in practice the pressure dependence of the experimental values. Best agreement of the results is obtained when the bulk susceptibility correction in rare gas solvents is evaluated from the analysis of the He-rare gas interactions, and when the shielding of deuterium in D_2-rare gas systems is considered.
Intermolecular forces and energies between ligands and receptors.
Moy, V T; Florin, E L; Gaub, H E
1994-10-14
The recognition mechanisms and dissociation pathways of the avidin-biotin complex and of actin monomers in actin filaments were investigated. The unbinding forces of discrete complexes of avidin or streptavidin with biotin analogs are proportional to the enthalpy change of the complex formation but independent of changes in the free energy. This result indicates that the unbinding process is adiabatic and that entropic changes occur after unbinding. On the basis of the measured forces and binding energies, an effective rupture length of 9.5 +/- 1 angstroms was calculated for all biotin-avidin pairs and approximately 1 to 3 angstroms for the actin monomer-monomer interaction. A model for the correlation among binding forces, intermolecular potential, and molecular function is proposed.
Evaluation of intermolecular forces in a circulating system.
Guo, Qiuquan; Liu, Mei; Yang, Jun
2011-11-01
Intercellular interactions, which are mediated by a variety of complex intercellular molecules through the processes of formation and dissociation of molecular bonds, play a critical role in regulating cellular functions in biological systems. Various approaches are applied to evaluate intercellular or molecular bonding forces. To quantify the intermolecular interaction forces, flow chamber has become a meaningful technique as it can ultimately mimic the cellular microenvironment in vivo under physiological flow conditions. Hydrodynamic forces are usually used to predict the intercellular forces down to the single molecular level. However, results show that only using hydrodynamic force will overestimate up to 30% of the receptor-ligand strength when the non-specific forces such as Derjaguin-Landau-Verway-Overbeek (DLVO) forces become un-neglected. Due to the nature of high ion concentration in the physiological condition, electrostatic force is largely screened which will cause DLVO force unbalanced. In this study, we propose to take account of the DLVO force, including van der Waals (VDW) force and electrostatic force, to predict the intermolecular forces of a cell doublet and cell-substrate model in a circulating system. Results also show that the DLVO force has a nonlinear effect as the cell-cell or cell-substrate distance changes. In addition, we used the framework of high accuracy hydrodynamic theories proved in colloidal systems. It is concluded that DLVO force could not be ignored in quantitative studies of molecular interaction forces in circulating system. More accurate prediction of intercellular forces needs to take account of both hydrodynamic force and DLVO force.
Macroscopic quantum resonators (MAQRO)
Kaltenbaek, Rainer; Kiesel, Nikolai; Romero-Isart, Oriol; Johann, Ulrich; Aspelmeyer, Markus
2012-01-01
Quantum physics challenges our understanding of the nature of physical reality and of space-time and suggests the necessity of radical revisions of their underlying concepts. Experimental tests of quantum phenomena involving massive macroscopic objects would provide novel insights into these fundamental questions. Making use of the unique environment provided by space, MAQRO aims at investigating this largely unexplored realm of macroscopic quantum physics. MAQRO has originally been proposed as a medium-sized fundamental-science space mission for the 2010 call of Cosmic Vision. MAQRO unites two experiments: DECIDE (DECoherence In Double-Slit Experiments) and CASE (Comparative Acceleration Sensing Experiment). The main scientific objective of MAQRO, which is addressed by the experiment DECIDE, is to test the predictions of quantum theory for quantum superpositions of macroscopic objects containing more than 10e8 atoms. Under these conditions, deviations due to various suggested alternative models to quantum th...
Energy Technology Data Exchange (ETDEWEB)
Schroer, Bert
2006-04-15
The holographic encoding is generalized to subalgebras of QFT localized in double cones. It is shown that as a result of this radically different spacetime encoding the modular group acts geometrically on the holographic image. As a result we obtain a formula for localization entropy which is identical to the previously derived formula for the wedge-localized subalgebra. The symmetry group in the holographic encoding turns out to be the Bondi-Metzner-Sachs group. (author)
DEFF Research Database (Denmark)
Cybulski, Hubert; Fernandez, Berta; Henriksen, Christian
2012-01-01
We evaluate the phenylacetylene-argon intermolecular potential energy surface by fitting a representative number of ab initio interaction energies to an analytic function. These energies are calculated at a grid of intermolecular geometries, using the CCSD(T) method and the aug-cc-pVDZ basis set ...
Intermolecular interactions in rifabutin—2-hydroxypropyl-β-cyclodextrin—water solutions
Anshakova, A. V.; Yermolenko, Yu. V.; Konyukhov, V. Yu.; Polshakov, V. I.; Maksimenko, O. O.; Gelperina, S. E.
2015-05-01
The possibility of a intermolecular complex rifabutin (RB)-2-hydroxypropyl-β-cyclodextrin (HP-β-CD) formed as a result of the interaction of the piperidine fragment of the RB molecule and the hydrophobic cavity of the HP-β-CD molecule was found. The stability constant of the intermolecular complex was determined.
Problem-Based Learning in 9th Grade Chemistry Class: "Intermolecular Forces"
Tarhan, Leman; Ayar-Kayali, Hulya; Urek, Raziye Ozturk; Acar, Burcin
2008-01-01
This research study aims to examine the effectiveness of a problem-based learning (PBL) on 9th grade students' understanding of intermolecular forces (dipole-dipole forces, London dispersion forces and hydrogen bonding). The student's alternate conceptions about intermolecular bonding and their beliefs about PBL were also measured. Seventy-eight…
Aguiar-Hualde, J. M.; Chiappe, G.; Louis, E.
2007-08-01
The effects of the on-site electron-electron (e-e) interaction U on the electronic transport across two longitudinally embedded quantum dots in the regime in which the antibonding (AB) state of the isolated composite system is aligned with the Fermi level at the leads are investigated. This regime occurs when the dot orbital energy γd is negative and equal in magnitude to the hopping probability between the orbitals on the two dots. In the noninteracting case, the conductance approaches asymptotically the conductance quantum G0=2e2/h as γd decreases; in addition, the contribution of the AB channel to the conductance tends to 1. As shown here, this picture is substantially modified by the e-e interaction. For finite U , the conductance versus γd shows a maximum at which the value G0 is reached, being supported in this case by the two channels (bonding and antibonding); the relative weight of each channel depends on the actual value of the e-e interaction. In the limit γd=-∞ , the conductance is supported only by the AB channel (as in the noninteracting case), but it is always smaller than G0 . While the mechanism underlying these results is mainly one body for small U , the Kondo effect and quantum interference come into play at large U . The effects of the e-e interaction increase significantly as the leads-dots coupling decreases, in particular, the range over which the conductance is non-negligible is significantly narrowed. The possible implications on a physically related system, a hydrogen molecule longitudinally bridging two Pt electrodes, are discussed.
Energy Technology Data Exchange (ETDEWEB)
Seo, Yoshiteru; Murakami, Masataka; Suzuki, Eiji; Watari, Hiroshi (National Institute for Physiological Sciences, Myodaiji, Okazaki (Japan)); Nagayama, Kuniaki (JEOL ltd., Akishima, Tokyo (Japan))
1990-01-23
Intracellular K of the perfused rat mandibular salivary gland was measured by {sup 39}K NMR spectroscopy at 8.45 T. Multiple-quantum NMR arising from multiple-exponential decay was used to eliminate the resonance due to extracellular K in the perfused gland at 25{degree}C. The resonance due to intracellular K consisted of two Lorentzian signals. These results suggest the possibility of the presence of a single homogeneous population of intracellular K with a correlation time of ca. 2.5 {times} 10 {sup {minus}8} s and a quadrupolar coupling constant ca. 1.4 MHz.
Energy Technology Data Exchange (ETDEWEB)
Markmann, Sergej, E-mail: sergej.markmann@ruhr-uni-bochum.de; Nong, Hanond, E-mail: nong.hanond@ruhr-uni-bochum.de; Hekmat, Negar; Jukam, Nathan [AG Terahertz Spektroskopie und Technologie, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Pal, Shovon [AG Terahertz Spektroskopie und Technologie, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Scholz, Sven; Kukharchyk, Nadezhda; Ludwig, Arne; Wieck, Andreas D. [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Dhillon, Sukhdeep; Tignon, Jérôme [Laboratoire Pierre Aigrain, Ecole Normale Supérieure, UMR 8551 CNRS, UPMC, Univ. Paris 6, 75005 Paris (France); Marcadet, Xavier [Alcatel-Thales III-V Lab, Route Départementale 128, 91767 Palaiseau Cedex (France); Bock, Claudia; Kunze, Ulrich [Lehrstuhl für Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)
2015-09-14
We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.
Indian Academy of Sciences (India)
KAUSHIK MAJI
2016-08-01
We propose a variant of the multiconfiguration time-dependent Hartree (MCTDH) method within the framework of Hermite-distributed approximating functional (HDAF) method. The discretized Hamiltonian is a highly banded Toeplitz matrix which significantly reduces computational cost in terms of both storage and number of operations. The method proposed is employed to carry out the study of tunnelling dynamics of two coupled double well oscillators. We have calculated the orthogonality time \\tau , which is a measure of the time interval for an initial state to evolve into its orthogonal state. It is observed that the coupling has a significant effect on \\tau .
Energy Technology Data Exchange (ETDEWEB)
Zheng, Rui [Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Centre for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); School of Mathematics and Information Science, North China University of Water Resources and Electric Power, Zhengzhou 450011 (China); Zheng, Limin; Yang, Minghui, E-mail: yplu@ntu.edu.sg, E-mail: yangmh@wipm.ac.cn [Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Centre for Magnetic Resonance, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Lu, Yunpeng, E-mail: yplu@ntu.edu.sg, E-mail: yangmh@wipm.ac.cn [Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371 (Singapore)
2015-10-21
Theoretical studies of the potential energy surface (PES) and bound states are performed for the N{sub 2}–N{sub 2}O van der Waals (vdW) complex. A four-dimensional intermolecular PES is constructed at the level of single and double excitation coupled-cluster method with a non-iterative perturbation treatment of triple excitations [CCSD(T)] with aug-cc-pVTZ basis set supplemented with bond functions. Two equivalent T-shaped global minima are located, in which the O atom of N{sub 2}O monomer is near the N{sub 2} monomer. The intermolecular fundamental vibrational states are assigned by inspecting the orientation of the nodal surface of the wavefunctions. The calculated frequency for intermolecular disrotation mode is 23.086 cm{sup −1}, which is in good agreement with the available experimental data of 22.334 cm{sup −1}. A negligible tunneling splitting with the value of 4.2 MHz is determined for the ground vibrational state and the tunneling splitting increases as the increment of the vibrational frequencies. Rotational levels and transition frequencies are calculated for both isotopomers {sup 14}N{sub 2}–N{sub 2}O and {sup 15}N{sub 2}–N{sub 2}O. The accuracy of the PES is validated by the good agreement between theoretical and experimental results for the transition frequencies and spectroscopic parameters.
Two-time quantum transport and quantum diffusion.
Kleinert, P
2009-05-01
Based on the nonequilibrium Green's function technique, a unified theory is developed that covers quantum transport and quantum diffusion in bulk semiconductors on the same footing. This approach, which is applicable to transport via extended and localized states, extends previous semiphenomenological studies and puts them on a firm microscopic basis. The approach is sufficiently general and applies not only to well-studied quantum-transport problems, but also to models, in which the Hamiltonian does not commute with the dipole operator. It is shown that even for the unified treatment of quantum transport and quantum diffusion in homogeneous systems, all quasimomenta of the carrier distribution function are present and fulfill their specific function. Particular emphasis is put on the double-time nature of quantum kinetics. To demonstrate the existence of robust macroscopic transport effects that have a true double-time character, a phononless steady-state current is identified that appears only beyond the generalized Kadanoff-Baym ansatz.
Polyelectrolyte brushes in mixed ionic medium studied via intermolecular forces
Farina, Robert; Laugel, Nicolas; Pincus, Philip; Tirrell, Matthew
2011-03-01
The vast uses and applications of polyelectrolyte brushes make them an attractive field of research especially with the growing interest in responsive materials. Polymers which respond via changes in temperature, pH, and ionic strength are increasingly being used for applications in drug delivery, chemical gating, etc. When polyelectrolyte brushes are found in either nature (e.g., surfaces of cartilage and mammalian lung interiors) or commercially (e.g., skin care products, shampoo, and surfaces of medical devices) they are always surrounded by mixed ionic medium. This makes the study of these brushes in varying ionic environments extremely relevant for both current and future potential applications. The polyelectrolyte brushes in this work are diblock co-polymers of poly-styrene sulfonate (N=420) and poly-t-butyl styrene (N=20) which tethers to a hydrophobic surface allowing for a purely thermodynamic study of the polyelectrolyte chains. Intermolecular forces between two brushes are measured using the SFA. As multi-valent concentrations are increased, the brushes collapse internally and form strong adhesion between one another after contact (properties not seen in a purely mono-valent environment).
Determination of stepsize parameters for intermolecular vibrational energy transfer
Energy Technology Data Exchange (ETDEWEB)
Tardy, D.C.
1992-03-01
Intermolecular energy transfer of highly excited polyatomic molecules plays an important role in many complex chemical systems: combustion, high temperature and atmospheric chemistry. By monitoring the relaxation of internal energy we have observed trends in the collisional efficiency ({beta}) for energy transfer as a function of the substrate's excitation energy and the complexities of substrate and deactivator. For a given substrate {beta} increases as the deactivator's mass increase to {approximately}30 amu and then exhibits a nearly constant value; this is due to a mass mismatch between the atoms of the colliders. In a homologous series of substrate molecules (C{sub 3}{minus}C{sub 8}) {beta} decreases as the number of atoms in the substrate increases; replacing F with H increases {beta}. All substrates, except for CF{sub 2}Cl{sub 2} and CF{sub 2}HCl below 10,000 cm{sup {minus}1}, exhibited that {beta} is independent of energy, i.e. <{Delta}E>{sub all} is linear with energy. The results are interpreted with a simple model which considers that {beta} is a function of the ocillators energy and its vibrational frequency. Limitations of current approximations used in high temperature unimolecular reactions were evaluated and better approximations were developed. The importance of energy transfer in product yields was observed for the photoactivation of perfluorocyclopropene and the photoproduction of difluoroethyne. 3 refs., 18 figs., 4 tabs.
Intermolecular Structural Change for Thermo-Switchable Polymeric photosensitizer
Energy Technology Data Exchange (ETDEWEB)
Park, Wooram; Park, Sin-Jung; Cho, Soojeong; Shin, Heejun; Jung, Young-Seok; Lee, Byeongdu; Na, Kun; Kim, Dong-Hyun
2016-08-31
A switchable photosensitizer (PS), which can be activated at a spe-cific condition beside light, has tremendous advantages for photo-dynamic therapy (PDT). Herein, we developed a thermo-switchable polymeric photosensitizer (T-PPS) by conjugating PS (Pheophor-bide-a, PPb-a) to a temperature-responsive polymer backbone of biocompatible hydroxypropyl cellulose (HPC). Self-quenched PS molecules linked in close proximity by pi-pi stacking in T-PPS were easily transited to an active monomeric state by the tempera-ture induced phase transition of polymer backbones. The tempera-ture responsive inter-molecular interaction changes of PS molecules in T-PPS were demonstrated in synchrotron small-angle X-ray scattering (SAXS) and UV-Vis spectrophotometer analysis. The T-PPS allowed switchable activation and synergistically enhanced cancer cell killing effect at the hyperthermia temperature (45 °C). Our developed T-PPS has the considerable potential not only as a new class of photomedicine in clinics but also as a biosensor based on temperature responsiveness.
When do we need attractive-repulsive intermolecular potentials?
Energy Technology Data Exchange (ETDEWEB)
Venkattraman, Ayyaswamy [School of Engineering, University of California, Merced, Merced, CA 95343 (United States)
2014-12-09
The role of attractive-repulsive interactions in direct simulation Monte Carlo (DSMC) simulations is studied by comparing with traditional purely repulsive interactions. The larger collision cross section of the long-range LJ potential is shown to result in a higher collision frequency and hence a lower mean free path, by at least a factor of two, for given conditions. This results in a faster relaxation to equilibrium as is shown by comparing the fourth and sixth moments of the molecular velocity distribution obtained using 0-D DSMC simulations. A 1-D Fourier-Couette flow with a large temperature and velocity difference between the walls is used to show that matching transport properties will result in identical solutions using both LJPA and VSS models in the near-continuum regime. However, flows in the transitional regime with Knudsen number, Kn ∼ 0.5 show a dependence on the intermolecular potential in spite of matching the viscosity coefficient due to differences in the collision frequency. Attractive-repulsive potentials should be used when both transport coefficients and collision frequencies should be matched.
Noncovalent Intermolecular Forces in Phycobilisomes of Porphyridium cruentum.
Zilinskas, B A; Glick, R E
1981-08-01
Using sensitized fluorescence as a measure of intactness of phycobilisomes isolated from Porphyridium cruentum, the effects of various environmental perturbations on phycobilisome integrity were investigated. The rate of phycobilisome dissociation in 0.75 ionic strength sodium salts proceeds in the order: SCN(-) > NO(3) (-) > Cl(-) > C(6)H(5)O(7) (3-) > SO(4) (2-) > PO(4) (3-), as predicted from the lyotropic series of anions and their effects on hydrophobic interactions in proteins. Similarly, increasing temperature (to 30 C) and pH values approaching the isoelectric points of the biliproteins stabilize phycobilisomes. Deuterium substitution at exchangeable sites on the phycobiliproteins decreases the rate of phycobilisome dissociation, while substitution at nonexchangeable sites increases rates of dissociation. It is concluded that hydrophobic intermolecular interactions are the most important forces in maintaining the phycobilisome structure. Dispersion forces also seem to contribute to phycobilisome stabilization. The adverse effects of electrostatic repulsion must not be ignored; however, it seems that the requirement of phycobilisomes of high salt concentrations is not simply countershielding of charges on the proteins.
Intermolecular forces between the motor protein and the filament.
Suda, H; Taylor, T W
1993-03-07
Intermolecular forces between motor proteins and filaments were evaluated on the basis of the experimental data of an in vitro motility assay by considering the molecular friction in the movement system. The molecular friction was caused by a different mechanism from that of the hydrodynamic drag. However, the molecular frictional forces apparently gave the same expression as the hydrodynamic frictional forces. The resulting equation was very effective in examining the physical properties of the weak interaction in the dynein-microtubules system from basic experiments carried out by Vale et al. (1989). From careful analysis of their experimental data, it was concluded that the hydrodynamic friction was not dominant, even in the weak binding state. The electrostatic interaction between dynein-heads and microtubules in the weak binding state was analyzed by applying the DLVO (Derjaguin-Landau-Verway-Overbeek) theory in colloid science through the ionic dependence of one-dimensional diffusion. The interacting distance between charges which took part in the weak adhesion was estimated to be 3 nm. In the present study, the molecular mechanism of the sliding velocity was also investigated for the myosin-actin filaments and the kinesin-microtubules systems by fitting the ATP-dependence and the ionic dependence in ATP-driven active sliding.
氦核双缝衍射实验的研究%Rsearch on Double-slit Diffraction of He with Quantum Theory
Institute of Scientific and Technical Information of China (English)
李春红; 吴坤朋; 张斯淇; 王婧; 郭义庆
2012-01-01
Using Schrdinger equation and KCL,we provided a new theoretical descr iption of the diffraction intensity pattern in double-slit experiments with He actom.And we also found the theory calculations and experiment data were consistent when the decoherence effect was considering.%应用薛定谔方程及基尔霍夫定律推导出一种新的关于氦核双缝衍射的强度计算公式,并利用新的衍射强度公式详细研究了氦核的双缝衍射问题.同时,我们也发现在考虑退相干效应时,理论与实验数据符合较好.
Fujii, Kazuhito
2010-01-01
We have discussed the Na + concentration dependence of the intermolecular distance of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) dimers in aqueous solution of NaOH. We have particularly focused on the S10-S00 transition of the PTCDA dimers which is sensitive to the intermolecular distance and we have found that the S10 state is split for the higher lying sublevel and the lower lying sublevel with the increase of the Na + concentrations. From the energy shift of the lower lying sublevel, we have estimated the intermolecular distance of the PTCDA dimer, that changes from 7.5 to 4.9 Å by the Na + concentration.
Institute of Scientific and Technical Information of China (English)
伍荣护; 赵化章; 于锡娟; 宋慧宇; 苏庆德
2001-01-01
The photoacoustic spectra of Eu(benz)3*(phen)2 (benz: benzoate, phen: phenanthroline) and Eu0.8Ln0.2(benz)3*(phen)2 (Ln3+: La3+ or Nd3+) were reported. The intermolecular energy transfer processes were studied from the point of the nonradiative transitions. Combined with the fluorescence spectroscopy, photoacoustic spectroscopy reflects the variation of the luminescence efficiencies of solid samples. The luminescence efficiency increases when La3+ is introduced, but it decreases greatly when Nd3+ is added, which is due to the difference of intermolecular energy transfer processes. The models of intramolecular and intermolecular energy transfer and relaxation processes were established.
Intermolecular Vibrations of the Complex of NO in the nsσ Rydberg States and Ar
Tsuji, Kazuhide; Shibuya, Kazuhiko; Obi, Kinichi
1995-01-01
The resonance enhanced multiphoton ionization method has been applied to the study of NO-Ar van der Waals complex in the nsσ (n = 3,4) Rydberg states. We have assigned the intermolecular vibrations appearing in the Ã—X˜ excitation spectrum of the complex. The bending structure appeared only with the excitation of the stretching mode in the Ã state, which was interpreted by intermolecular forces. The E˜-Ã excitation spectra were independent of the initial intermolecular level in the Ã state an...
Institute of Scientific and Technical Information of China (English)
张蔚曦; 张愉; 金慧
2016-01-01
The characteristics of optical absorption in an asymmetric four-level N-type semiconductor quantum well with the cross-coupling longitude-optical phonons (CCLOP) relaxation were studied. In the linear range, it shows that the electromagnetically induced transparency (EIT) relies on the coherence control of the optical fields and the CCLOP relaxation. Especially, there exhibits a double-EIT when the transition frequency between the hole and anti-bonding states is rather large. Interestingly, there appears a near-perfect double-EIT phenomenon when increasing the CCLOP relaxation. It is expected that these results may exhibit some potential applications in the all-optical switching and other optical information engineering related issues.%对在交叉耦合纵波光学声子（Cross-coupling Longitude-optical Phonons，简称CCLOP）弛豫时四能级非对称N型半导体量子阱系统的光吸收特性进行了研究。研究表明，在线性范围内，在该系统中能够实现电磁感应透明效应（Electromagnetically Induced Transparency，简称EIT），并且这种EIT效应依赖于光场与系统的谐振控制和CCLOP 弛豫；尤其是当空穴态和反键态之间的跃迁频率较大时，系统会出现双EIT现象。有趣的是，当CCLOP弛豫增大时，将出现近乎完美的双EIT现象。研究结果在全光开关和其他的光信息工程中有着潜在的应用。
The Double Slit Experiment With Polarizers
Holden, M; Sherry, T N
2011-01-01
The double slit experiment provides a standard way of demonstrating how quantum mechanics works. We consider modifying the standard arrangement so that a photon beam incident upon the double slit encounters a polarizer in front of either one or both of the slits.
Energy Technology Data Exchange (ETDEWEB)
El-Kader, M.S.A., E-mail: mohamedsay68@hotmail.com [Department of Engineering Mathematics and Physics, Faculty of Engineering, Giza 12211 (Egypt); Mostafa, S.I. [Department of Engineering Mathematics and Physics, Faculty of Engineering, Giza 12211 (Egypt); Bancewicz, T. [Faculty of Physics, Department of Nonlinear Optics, Umultowska 85, 61-614 Poznań (Poland); Maroulis, G. [Department of Chemistry, University of Patras, GR-26500 Patras (Greece)
2014-08-31
Highlights: • We have determined an isotropic intermolecular potential for the interaction of nitrogen. • The thermophysical and transport properties are calculated for this gas. • We have adopted a model for the induced dipole moment μ(r) with adjustable parameters. • The induced trace polarizability model are constructed for scattering. • The quantum lineshapes of absorption and scattering are calculated. - Abstract: The rototranslational collision-induced absorption (CIA) at different temperatures and collision-induced light scattering (CILS) at room temperature of nitrogen gas are analyzed in terms of new isotropic intermolecular potential, multipole-induced dipole functions and interaction-induced pair polarizability models, using quantum spectral lineshape computations. The irreducible spherical form for the induced operator of light scattering mechanisms was determined. The high frequency wings are discussed in terms of the collision-induced rotational Rayleigh effect and estimates for the dipole–octopole polarizability E{sub 4}, is obtained and checked with the ab initio theoretical value. The quality of the present potential has been checked by comparing between calculated and experimental thermo-physical and transport properties over a wide temperature range, which are found to be in good agreement.
Arias-Hernández, L. A.; Morales-Serrano, A. F.
2002-11-01
In this work we follow the Bender et al paper [1] to study the quantum analogues of the Stirling and Ericsson polytropic cycles. In the context of the classical thermodynamics, the Stirling and Ericsson cycles correspond to reversible heat engines with two isothermal processes joined by two polytropic branches which occur in a device called regenerator. If this device is an ideal one, the efficiency of these cycles is the Carnot efficiency. Here, we introduce the quantum analogues of the Stirling and Ericsson cycles, the first one based on a double square potential well with a finite potential barrier, since in this system the tunnel effect could be the analogue to the regeneration classical process, therefore the isochoric quantum branches would really correspond to an internal energy storage, and the last one with an unknown system where the isobaric quantum processes don't induce changes in its quantum state. With these systems the quantum engines have cycles consisting of polytropic and isothermal quantum processes analogues to the corresponding classical processes. We show that in both cases the quantum cycles have an efficiency given by ηCQM = 1 - EC/EH, which is the same expression for the quantum analogue of the Carnot cycle studied by Bender.
Energy Technology Data Exchange (ETDEWEB)
El-Kader, M.S.A., E-mail: Mohamedsay68@hotmail.com [Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza 12211 (Egypt); Maroulis, G. [Department of Chemistry, University of Patras, GR-26500 Patras (Greece); Bich, E. [Institut fuer Chemie, Universitaet Rostock Albert-Einstein-Strasse 3a, D-18059 Rostock (Germany)
2012-07-25
Highlights: Black-Right-Pointing-Pointer We have determined an isotropic intermolecular potential for the interaction of hydrogen. Black-Right-Pointing-Pointer The thermophysical and transport properties are calculated for this system. Black-Right-Pointing-Pointer The rovibrational energy levels and scattering cross-sections are determined. Black-Right-Pointing-Pointer We have adopted a model for the induced dipole moment {mu}(r) with adjustable parameters. Black-Right-Pointing-Pointer The quantum lineshapes of absorption and scattering are calculated. -- Abstract: Quantum mechanical lineshapes of collision-induced absorption (CIA) at different temperatures and of collision-induced light scattering (CILS) at room temperature are computed for gaseous molecular hydrogen using theoretical values for induced dipole moments and pair-polarizability trace and anisotropy as input. Comparison with measured spectra of absorption, isotropic and anisotropic light scattering shows satisfactory agreement, for which the uncertainty in measurement of its spectral moments is seen to be large. Empirical models of the dipole moment and pair-polarizability trace and anisotropy which reproduce the experimental spectra and the first three spectral moments more closely than the fundamental theory are also given. Good agreement between computed and experimental lineshapes of both absorption and scattering is obtained when potential models which are constructed from the thermophysical, transport, total scattering cross-section and spectroscopic properties are used. Also, the use of the new potential in lattice dynamic calculations yields good results for several properties of solid hydrogen.
Li, Shu-Shen; Long, Gui-lu; Bai, Feng-Shan; Feng, Song-Lin; Zheng, Hou-Zhi
2001-01-01
Quantum computing is a quickly growing research field. This article introduces the basic concepts of quantum computing, recent developments in quantum searching, and decoherence in a possible quantum dot realization.
Quantum cluster algebras and quantum nilpotent algebras
Goodearl, Kenneth R.; Yakimov, Milen T.
2014-01-01
A major direction in the theory of cluster algebras is to construct (quantum) cluster algebra structures on the (quantized) coordinate rings of various families of varieties arising in Lie theory. We prove that all algebras in a very large axiomatically defined class of noncommutative algebras possess canonical quantum cluster algebra structures. Furthermore, they coincide with the corresponding upper quantum cluster algebras. We also establish analogs of these results for a large class of Poisson nilpotent algebras. Many important families of coordinate rings are subsumed in the class we are covering, which leads to a broad range of applications of the general results to the above-mentioned types of problems. As a consequence, we prove the Berenstein–Zelevinsky conjecture [Berenstein A, Zelevinsky A (2005) Adv Math 195:405–455] for the quantized coordinate rings of double Bruhat cells and construct quantum cluster algebra structures on all quantum unipotent groups, extending the theorem of Geiß et al. [Geiß C, et al. (2013) Selecta Math 19:337–397] for the case of symmetric Kac–Moody groups. Moreover, we prove that the upper cluster algebras of Berenstein et al. [Berenstein A, et al. (2005) Duke Math J 126:1–52] associated with double Bruhat cells coincide with the corresponding cluster algebras. PMID:24982197
Institute of Scientific and Technical Information of China (English)
詹志明; 刘晓东; 张立辉; 石文星; 李星
2011-01-01
Propose a scheme to realize multi-qubit GHZ states in superconducting quantum-interference devices（SQUIDs） via double Raman transition.In this scheme,the cavity field is only virtually excited and thus the cavity decay can be ignored.The GHZ states are realized by using only two basic states of the SQUID system and the relaxation of excited state of the system are avoided.Base on the points mentioned above,the scheme should be easily realized on experiment.%在腔中通过双Raman作用,在超导量子干涉器件中实现多比特GHZ（Greenberger-Horne-Zeilinger）态的制备.在制备过程中,由于腔场只是被虚激发的,所以腔模的衰减可以忽略.GHZ态的实现只用到了超导系统的两个基态,有效地避免了超导系统激发态的弛豫.
Institute of Scientific and Technical Information of China (English)
解光军; 杨俊安; 庄镇泉
2003-01-01
本文利用量子理论中的双缝干涉实验(Double-slit Interference Experiment)构造了一种全新的量子神经网络(Quantum Neural Network,QNN)模型.通过理论分析,推导出该模型的动力学表达式,并给出相应的训练算法.仿真实验表明,该模型具有学习布尔逻辑函数的功能,特别是两层网络结构能够实现类似异或(XOR)逻辑的学习,体现出了量子计算对传统神经网络的优越性.本文的研究为探索神经网络与量子计算的结合提供了一个新的途径.
Shi, Bei; Lau, Kei May
2016-01-01
The effects of a double-cap procedure on the optical properties of an InAs/InAlGaAs quantum dots (QDs) system grown by metal-organic chemical vapor deposition (MOCVD) have been investigated by atomic force microscopy (AFM) and room temperature photoluminescence (RT-PL) spectroscopy. An optimized QD growth condition has been achieved, with an areal density of 4.6×1010 cm-2. It was found that the thickness and lattice constant of the high temperature second cap layer (SCL) were crucial for improving the integrated PL intensity and line-width of the 1.55 μm emission from the InAs/InAlGaAs QD system grown on a semi-insulating InP (100) substrate. With fine-tuned SCL thickness and lattice constant, the optical performance of the five-stack QDs was enhanced. The improvements can be attributed to the smooth growth front, observed from the AFM images, and the well-balanced stress engineering.
Quesada-Moreno, María Mar; Avilés-Moreno, Juan Ramón; Márquez-García, A A; López-González, Juan Jesús
2014-06-01
The behavior of L-cysteine (C3H7NO2S, (2R)-2-amino-3-sulfanylpropanoic acid) in water at different pH values was analyzed both experimentally and theoretically. The behavior was studied at pH values of 5.21 (at this pH, L-cysteine is a zwitterionic species), 1.00 (protonated species), 8.84 (monodeprotonated species), and 13.00 (dideprotonated species). We carried out a vibrational study using nonchiroptical (IR-Raman) and chiroptical (VCD) techniques complemented by quantum chemical calculations. We adopted a dual strategy, as follows. (i) The hybrid density functionals B3LYP and M062X and the ab initio MP2 method were employed, with the same 6-311++G (d,p) basis set, in order to characterize the relative energies and structures of an extensive set of conformers of L-cysteine. The presence of water was included by utilizing the IEF-PCM implicit solvation model. (ii) The vibrational analysis was made using a chirality-sensitive using a chirality-sensitive technique (VCD) and chirality-insensitive techniques (IR, including MIR and FIR, and Raman), especially in aqueous solution. The results obtained theoretically and experimentally were compared in order to deduce the most stable structures at each pH. Moreover, for the first time, the monodeprotonated anion of L-cysteine was detected in aqueous solution by means of IR, Raman and vibrational circular dichroism (VCD). Finally, analysis of the low-frequency region using the IR and Raman techniques was shown to be a very important way to understanding the conformational preference of the zwitterionic species.
Intermolecular disulfide bond influences unphosphorylated STAT3 dimerization and function.
Butturini, Elena; Gotte, Giovanni; Dell'Orco, Daniele; Chiavegato, Giulia; Marino, Valerio; Canetti, Diana; Cozzolino, Flora; Monti, Maria; Pucci, Piero; Mariotto, Sofia
2016-10-01
Signal transducer and activator of transcription 3 (STAT3) is a transcription factor activated by the phosphorylation of tyrosine 705 in response to many cytokines and growth factors. Recently, the roles for unphosphorylated STAT3 (U-STAT3) have been described in response to cytokine stimulation, in cancers, and in the maintenance of heterochromatin stability. It has been reported that U-STAT3 dimerizes, shuttles between the cytoplasm and nucleus, and binds to DNA, thereby driving genes transcription. Although many reports describe the active role of U-STAT3 in oncogenesis in addition to phosphorylated STAT3, the U-STAT3 functional pathway remains elusive.In this report, we describe the molecular mechanism of U-STAT3 dimerization, and we identify the presence of two intermolecular disulfide bridges between Cys367 and Cys542 and Cys418 and Cys426, respectively. Recently, we reported that the same cysteines contribute to the redox regulation of STAT3 signaling pathway both in vitro and in vivo The presence of these disulfides is here demonstrated to largely contribute to the structure and the stability of U-STAT3 dimer as the dimeric form rapidly dissociates upon reduction in the S-S bonds. In particular, the Cys367-Cys542 disulfide bridge is shown to be critical for U-STAT3 DNA-binding activity. Mutation of the two Cys residues completely abolishes the DNA-binding capability of U-STAT3. Spectroscopic investigations confirm that the noncovalent interactions are sufficient for proper folding and dimer formation, but that the interchain disulfide bonds are crucial to preserve the functional dimer. Finally, we propose a reaction scheme of U-STAT3 dimerization with a first common step followed by stabilization through the formation of interchain disulfide bonds. © 2016 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.