arXiv:physics/0211119

Some Aspects of Dynamical Tunneling in Two Dimensional Coupled States

Dmytro Babyuk

Published Nov 28, 2002• 0 citations

Abstract

Process of dynamical tunneling in two-dimensional coupled potentials is considered within Bohmian approach to quantum mechanics. Quantum trajectories tend to go along the paths where potential energy increases and then decreases. It leads to a suggestion that dynamical and barrier tunneling are the same processes but the former is hidden due to specific potential surface.

DOI: 10.48550/arxiv.physics/0211119

Related papers

Hydrodynamic analysis of dynamical tunneling

Dmytro Babyuk, Róbert E. Wyatt, John H. Frederick

The process of dynamical tunneling between local mode states is analyzed within the Bohmian approach to quantum mechanics. A number of quantum trajectories are followed for both a coupled Morse potential and the Barbanis potential. The superposition of nearly degenerate eigenstates leads to the formation of numerous permanent nodes concentrated near the potential valley. Around these nodes, vortices are evident on the flux map. Quantum trajectories can be attracted by a vortex and their velocity and kinetic energy will be significantly changed as they spiral around the vortex. However, trajectories starting remotely from vortices reflect more realistically the transition between a pair of localized states. These quantum trajectories can go through one or more regions where the potential energy is higher than the total energy. Hence, barrier tunneling accompanies dynamical tunneling.

The Journal of Chemical PhysicsSep 18, 200315 citations

Effective quantum tunneling from a semiclassical momentous approach

Luis Aragón-Muñoz, Guillermo Chacón‐Acosta, Héctor H. Hernández

In this work, we study the quantum tunnel effect through a potential barrier within a semiclassical formulation of quantum mechanics based on expectation values of configuration variables and quantum dispersions as dynamical variables. The evolution of the system is given in terms of a dynamical system for which we are able to determine numerical effective trajectories for individual particles, similar to the Bohmian description of quantum mechanics. We obtain a complete description of the possible trajectories of the system, finding semiclassical reflected, tunneled and confined paths due to the appearance of an effective time-dependent potential.

arXiv:2004.00118International Journal of Modern Physics BOct 28, 202013 citations

Quantum Phase Spase Representation for Double Well Potential

Dmytro Babyuk

A behavior of quantum states (superposition of two lowest eigenstates, Gaussian wave packet) in phase space is studied for one and two dimensional double well potential. Two dimensional potential is constructed from double well potential coupled linearly and quadratically to harmonic potential. Quantum trajectories are compared with classical ones. Preferable tunneling path in phase space is found. An influence of energy of initial Gaussian wave packet and trajectory initial condition on tunneling process is analyzed.. Coupling effect on trajectories and preferable tunneling path for two dimensional potential is studied.

arXiv:physics/0208070Aug 19, 20020 citations

Dynamical tunneling of bound systems through a potential barrier: Complex way to the top

Fedor L. Bezrukov, D. Levkov

A semiclassical method of complex trajectories for the calculation of the tunneling exponent n systems with many degrees of freedom is further developed. It is supplemented with an easily implemented technique that enables one to single out the physically relevant trajectory from the whole set of complex classical trajectories. The method is applied to semiclassical transitions of a bound system through a potential barrier. We find that the properties of physically relevant complex trajectories are qualitatively different in the cases of potential tunneling at low energy and dynamical tunneling at energies exceeding the barrier height. Namely, in the case of high energies, the physically relevant complex trajectories describe tunneling via creation of a state close to the top of the barrier. The method is checked against exact solutions of the Schrödinger equation in a quantum-mechanical system of two degrees of freedom.

arXiv:quant-ph/0312144Journal of Experimental and Theoretical PhysicsApr 1, 200429 citations

Dynamical tunneling of bound systems through a potential barrier: complex way to the top

Fedor L. Bezrukov, D. G. Levkov

A semiclassical method of complex trajectories for the calculation of the tunneling exponent in systems with many degrees of freedom is further developed. It is supplemented with an easily implementable technique, which enables one to single out the physically relevant trajectory from the whole set of complex classical trajectories. The method is applied to semiclassical transitions of a bound system through a potential barrier. We find that the properties of physically relevant complex trajectories are qualitatively different in the cases of potential tunneling at low energy and dynamical tunneling at energies exceeding the barrier height. Namely, in the case of high energies, the physically relevant complex trajectories describe tunneling via creation of a state close to the top of the barrier. The method is checked against exact solutions of the Schrodinger equation in a quantum mechanical system of two degrees of freedom.

Dec 16, 200324 citations

Dynamical Tunneling and Control

Srihari Keshavamurthy

Tunneling is a supreme quantum effect. Every introductory text [1] on quantum mechanics gives the paradigm example of a particle tunneling through a one-dimensional potential barrier despite having a total energy less than the barrier height. Indeed, the reader typically works through a number of exercises, all involving one-dimensional potential barriers of one form or another modeling several key physical phenomena ranging from atom transfer reactions to the decay of α-particles [2]. However, one seldom encounters coupled multidimenisonal tunneling in such texts since an analytical solution of the Schro¨dinger equation in such cases is not possible. Interestingly, the richness and complexity of the tunneling phenomenon manifest themselves in full glory in the case of multidimensional systems [3]. Thus, for instance, the usual one-dimensional expectation of increasing tunneling splittings as one approaches the barrier top from below is not necessarily true as soon as one couples another bound degree of freedom to the tunneling coordinate. In the context of molecular reaction dynamics, multidimensional tunneling can result in strong mode-specificity and fluctuations in the reaction rates [4]. In fact, a proper description of tunneling of electrons and hydrogen atoms is absolutely essential [5,6] even in molecular systems as large as enzymes and proteins. Although one usually assumes tunneling effects to be significant in molecules involving light atom transfers, it is worth pointing out that neglecting the tunneling of even a heavy atom like carbon is the difference between a reaction occurring or not occurring. In particular, one can underestimate rates by nearly hundred orders of magnitude [7]. Interestingly, and perhaps paradoxically, several penetrating insights into the nature and mechanism of multidimensional barrier tunneling have been obtained from a phase-space perspective [8,9]. The contributions by Creagh, Shudo and Ikeda, and Takahashi in the present volume provide a detailed account of the latest advances in the phasespace-based understanding of multidimensional barrier tunneling.

CRC Press eBooksMar 9, 20112 citations