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Ping Ao

Publications and source records attributed to Ping Ao.

44 records · Page 3Linked to original sources
arXiv1996

Influence of typical environments on quantum processes

We present the results of studying the influence of different environmental states on the coherence of quantum processes. We choose to discuss a simple model which describe two electronic reservoirs connected through tunneling via a resonant state. The model could, e.g., serve as an idealization of inelastic resonant tunneling through a double barrier structure. We develop Schwinger's closed time path formulation of non-equilibrium quantum statistical mechanics, and show that the influence of the environment on a coherent quantum process can be described by the value of a generating functional at a specific force value, thereby allowing for a unified discussion of destruction of phase coherence by various environmental states: thermal state, classical noise, time dependent classical field, and a coherent state. The model allows an extensive discussion of the influence of dissipation on the coherent quantum process, and expressions for the transmission coefficient are obtained in the possible limits.

cond-mat↗
arXiv1995

A Scenario to the Anomalous Hall Effect in the Mixed State of Superconductors

We argue that the motion of vacancies in a pinned vortex lattice may dominate the contribution to the Hall effect in an appropriate parameter regime for a superconductor. Based on this consideration a model is constructed to explain the anomalous Hall effect without any modification of the basic vortex dynamic equation. Quantitative predictions are obtained. Present model can be directly tested by an observation of the vacancy motion.

cond-mat↗
arXiv1994

Magnetic Field Effect on an Electron Tunneling out of a Confining Plane

The influence of a magnetic field on the tunneling of an electron out of a confining plane is studied by a path integral method. We map this 3-d problem on to a 1-d one, and find that the tunneling is strongly affected by the field. Without a perpendicular field the tunneling at zero temperature can be completely suppressed by a large parallel field, but in the small parallel field and low temperature limit the tunneling rate is finite. An explicit formula is obtained in this case. A quantitative explanation without fitting parameter to a recent experiment is provided.

cond-mat↗
arXiv1994

Nonlinear Schrödinger Equation for Superconductors

Using the Hartree-Fock-Bogoliubov factorization of the density matrix and the Born-Oppenheimer approximation we show that the motion of the condensate satisfies a nonlinear Schrödinger equation in the zero temperature limit. The Galilean invariance of the equation is explicitly manifested. {}From this equation some general properties of a superconductor, such as Josephson effects, the Magnus force, and the Bogoliubov-Anderson mode can be obtained readily.

cond-mat↗
arXiv1993

Tunneling of a Quantized Vortex: Roles of Pinning and Dissipation

We have performed a theoretical study of the effects of pinning potential and dissipation on vortex tunneling in superconductors. Analytical results are obtained in various limits relevant to experiment. In general we have found that pinning and dissipation tend to suppress the effect of the vortex velocity dependent part of the Magnus force on vortex tunneling.

cond-mat↗
arXiv1993

Escape of trapped electrons from a helium surface: a dynamical theory

We present a dynamical theory which incorporates the electron-electron correlations and the effects of external magnetic fields for an electron escaping from a helium surface. Analytical expressions for the escape rate can be obtained in various limits. In particular, the tunneling rate with a parallel magnetic field is presented explicitly.

cond-mat↗
arXiv1993

Dynamical Correlation Theory for an Escape Process

A dynamical theory which incorporates the electron-electron correlations and the effects of external magnetic fields for an electron escaping from a helium surface is presented. The degrees of freedom in the calculation of the escape rate is reduced from $3N$ to 3 as compared with other approach. Explicit expressions for the escape rate in various situations are obtained. In particular, in the weak parallel magnetic field limit the tunneling rate has an exponential dependence quadratic with magnetic field strength and an unusual exponential increase linear with temperature.

cond-mat↗