共查询到20条相似文献,搜索用时 218 毫秒
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We report on new developments in the quantum picture of correlated electron transport in charge and spin density waves. The model treats the condensate as a quantum fluid in which charge soliton domain wall pairs nucleate above a Coulomb blockade threshold field. We employ a time-correlated soliton tunneling model, analogous to the theory of time-correlated single electron tunneling, to interpret the voltage oscillations and nonlinear current-voltage characteristics above threshold. An inverse scaling relationship between threshold field and dielectric response, originally proposed by Grüner, emerges naturally from the model. Flat dielectric and other ac responses below threshold in NbSe3 and TaS3, as well as small density wave phase displacements, indicate that the measured threshold is often much smaller than the classical depinning field. In some materials, the existence of two distinct threshold fields suggests that both soliton nucleation and classical depinning may occur. In our model, the ratio of electrostatic charging to pinning energy helps determine whether soliton nucleation or classical depinning dominates. 相似文献
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A new method is proposed for ab initio calculations of nonstationary quantum processes on the basis of a probability representation of quantum mechanics with the help of a positive definite function (quantum tomogram). The essence of the method is that an ensemble of trajectories associated with the characteristics of the evolution equation for the quantum tomogram is considered in the space where the quantum tomogram is defined. The method is applied for detailed analysis of transient tunneling of a wave packet. The results are in good agreement with the exact numerical solution to the Schrödinger equation for this system. The probability density distributions are obtained in the coordinate and momentum spaces at consecutive instances. For transient tunneling of a wave packet, the probability of penetration behind the barrier and the time of tunneling are calculated as functions of the initial energy. 相似文献
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C. Wetterich 《Physics letters. A》2012,376(5):706-712
We describe both quantum particles and classical particles in terms of a classical statistical ensemble, with a probability distribution in phase space. By use of a wave function in phase space both can be treated in the same quantum formalism. Quantum particles are characterized by a specific choice of observables and time evolution of the probability density. Then interference and tunneling are found within classical statistics. Zwitters are (effective) one-particle states for which the time evolution interpolates between quantum and classical particles. Experimental bounds on a small parameter can test quantum mechanics. 相似文献
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The possibility to formulate classical statistical mechanics in terms of the complex wave function and density matrix obeying
the evolution equation is discussed. It is shown that the modulus squared of the introduced wave function of the classical
particle has the same physical meaning as the modulus squared of the wave function of the quantum particle. The tomographic
probabilities are studied for both classical and quantum states. Integrals of motion and their relation to the propagators
are discussed. 相似文献
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Considering the Maxwell equations for the electromagnetic-field propagation in a solid with a three-dimensional superlattice
of quantum dots linked by strong tunneling along one axis, we obtained a phenomenological equation in the form of the classical
2+1-dimensional sine-Gordon equation. Electrons were considered classically in the formalism of the Boltzmann kinetic equation
for the distribution function. Solutions were obtained as a soliton lattice for the vector potential of the electric field.
These lattices emerge as a consequence of the coherent change of the classical distribution function and the electric field
generated by tunneling electrons in a system of quantum wells. 相似文献
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Naoufel Ben Abdallah 《Journal of statistical physics》1998,90(3-4):627-662
Interface conditions between a classical transport model described by the Boltzmann equation and a quantum model described by a set of Schrödinger equations are presented in the one-dimensional stationary setting. These interface conditions, derived thanks to an asymptotic analysis of the Wigner transform, are shown to be flux-preserving and are used to build a hybrid model consisting of a quantum zone surrounded by two classical ones. The hybrid model is shown to be well posed when the potential is either prescribed or computed self-consistently, and the semiclassical limit of the problem is shown to give the right interface conditions between two kinetic regions (the electrostatic potential being fixed). This model can be used to describe far-from-equilibrium electron transport in a resonant tunneling diode. 相似文献
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With the progress of LSI technology, the electronic device size is scaled down to the sub 0.1μ m region. In such an ultrasmall device, it is indispensable to take quantum mechanical effects into account in device modeling. In this paper, we present a newly developed quantum Monte Carlo device simulation applicable to ultrasmall semiconductor devices. In this model, the quantum effects are represented in terms of quantum mechanically corrected potential in the classical Boltzmann equation. It is demonstrated that the quantum transport effects such as tunneling and energy quantization in ultrasmall semiconductor devices are obtained for the first time by using the standard Monte Carlo techniques. 相似文献
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原子通过激光冷却技术能够被制备在低温状态,这时冷原子云会展现出量子力学的波动性.研究了一束冷原子入射到一个蓝失谐的激光束上所表现出的量子力学隧穿效应.蓝失谐的激光束相对于冷原子而言等效于一个量子力学势垒.根据二能级模型,在理论上分析了具有内部结构的原子矢量物质波穿过激光束的量子力学反射与透射,特别是对原子穿越激光束所需的时间——量子隧穿时间进行了详细的研究.量子力学波动性使得冷原子穿越一个激光束时明显地展现出与经典粒子(热原子)不同的结果.
关键词:
冷原子
原子光学
量子隧穿 相似文献
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Gerritsma R Lanyon BP Kirchmair G Zähringer F Hempel C Casanova J García-Ripoll JJ Solano E Blatt R Roos CF 《Physical review letters》2011,106(6):060503
We report on quantum simulations of relativistic scattering dynamics using trapped ions. The simulated state of a scattering particle is encoded in both the electronic and vibrational state of an ion, representing the discrete and continuous components of relativistic wave functions. Multiple laser fields and an auxiliary ion simulate the dynamics generated by the Dirac equation in the presence of a scattering potential. Measurement and reconstruction of the particle wave packet enables a frame-by-frame visualization of the scattering processes. By precisely engineering a range of external potentials we are able to simulate text book relativistic scattering experiments and study Klein tunneling in an analogue quantum simulator. We describe extensions to solve problems that are beyond current classical computing capabilities. 相似文献
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We argue that many major features in electronic transport in realistic quantum dots are not explainable by the usual semiclassical approach, due to the contributions of the quantum-mechanical tunneling of the electrons through the Kolmogorov-Arnol'd-Moser islands. We show that dynamical tunneling gives rise to a set of resonances characterized by two quantum numbers, which leads to conductance oscillations and concentration of wave functions near stable and unstable periodic orbits. Experimental results agree very well with our theoretical predictions, indicating that tunneling has to be taken into account to understand the physics of transport in generic nanostructures. 相似文献
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We investigate quantum Brownian motion sustained transport in both, adiabatically rocked ratchet systems and quantum stochastic resonance (QSR). Above a characteristic crossover temperature T(0) tunneling events are rare; yet they can considerably enhance the quantum-noise-driven particle current and the amplification of signal output in comparison to their classical counterparts. Below T(0) tunneling prevails, thus yielding characteristic novel quantum transport phenomena. For example, upon approaching T=0 the quantum current in Brownian motors exhibits a tunneling-induced reversal, and tends to a finite limit, while the classical result approaches zero without such a change of sign. As a consequence, similar current inversions generated by quantum effects follow upon variation of the particle mass or of its friction coefficient. Likewise, in this latter regime of very low temperatures the tunneling dynamics becomes increasingly coherent, thus suppressing the semiclassically predicted QSR. Moreover, nonadiabatic driving may cause driving-induced coherences and quantized resonant transitions with no classical analog. (c) 1998 American Institute of Physics. 相似文献
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Basic mathematical apparatus of quantum mechanics like the wave function, probability density, probability density current, coordinate and momentum operators, corresponding commutation relation, Schrödinger equation, kinetic energy, uncertainty relations and continuity equation is discussed from the point of view of mathematical statistics. It is shown that the basic structure of quantum mechanics can be understood as generalization of classical mechanics in which the statistical character of results of measurement of the coordinate and momentum is taken into account and the most important general properties of statistical theories are correctly respected. 相似文献
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S. Longhi 《Applied physics. B, Lasers and optics》2011,104(3):453-468
Spatial and/or temporal propagation of light waves in periodic optical structures offers a unique possibility to realize in
a purely classical setting the optical analogues of a wide variety of quantum phenomena rooted in relativistic wave equations.
In this work a brief overview of a few optical analogues of relativistic quantum phenomena, based either on spatial light
transport in engineered photonic lattices or on temporal pulse propagation in Bragg grating structures, is presented. Examples
include spatial and temporal photonic analogues of the Zitterbewegung of a relativistic electron, Klein tunneling, vacuum
decay and pair production, the Dirac oscillator, the relativistic Kronig–Penney model, and optical realizations of non-Hermitian
extensions of relativistic wave equations. 相似文献
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LIN Qiong-Gui 《理论物理通讯》2006,45(5):919-922
In quantum mechanics the center of a wave packet is precisely defined as the center of probability. The center-of-probability velocity describes the entire motion of the wave packet.
In classical physics there is no precise counterpart to the
center-of-probability velocity of quantum mechanics, in spite of the fact that there exist in the literature at least eight different velocities for
the electromagnetic wave. We propose a center-of-energy velocity to
describe the entire motion of general wave packets in classical
physical systems. It is a measurable quantity, and is well defined
for both continuous and discrete systems. For electromagnetic wave
packets it is a generalization of the velocity of energy transport.
General wave packets in several classical systems are studied and the
center-of-energy velocity is calculated and expressed in terms of the
dispersion relation and the Fourier coefficients. These systems
include string subject to an external force, monatomic chain and
diatomic chain in one dimension, and classical Heisenberg model in
one dimension. In most cases the center-of-energy velocity reduces to
the group velocity for quasi-monochromatic wave packets. Thus it also
appears to be the generalization of the group velocity. Wave packets
of the relativistic Dirac equation are discussed briefly. 相似文献
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We study the problem of classical particle in linear potential using the formalism of Hilbert space and tomographic-probability distribution. We solve the Liouville equation for this problem by finding the density matrix satisfying a von Newmann-like equation in the form of a product of the wave functions. We discuss the relation of the classical solution obtained to quantum mechanics. 相似文献
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We consider a quantum system coupled to a dissipative background with many degrees of freedom using the Monte Carlo wave function method. Instead of dealing with a density matrix which can be very highly dimensional, the method consists of integrating a stochastic Schr?dinger equation with a non-Hermitian damping term in the evolution operator, and with random quantum jumps. The method is applied to the diffusion of hydrogen on the Ni(111) surface below 100 K. We show that the recent experimental diffusion data for this system can be understood through an interband activation process, followed by quantum tunneling. 相似文献
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建立了夸克胶子等离子体中胶子的经典输运方程, 并讨论了它与胶子的量子输运方程以及它与夸克的经典输运方程之间的关系. 相似文献