Landau problem with a general time-dependent electric field

TL;DR

This paper derives an explicit, physically interpretable factorization of the time evolution operator for the Landau problem with a general time-dependent electric field, elucidating geometric, dynamical, and nonadiabatic effects.

Contribution

It provides a novel explicit factorization of the evolution operator in the Landau problem with time-dependent electric fields, including geometric and nonadiabatic components.

Findings

Explicit factorization of the time evolution operator.

Identification of geometric and nonadiabatic contributions.

Formula for nonadiabatic transition probabilities.

Abstract

The time evolution is studied for the Landau problem with a general time dependent electric field ${\bf E}(t)$ in a plane perpendicular to the magnetic field. A general and explicit factorization of the time evolution operator is derived with each factor having a clear physical interpretation. The factorization consists of a geometric operator (path-ordered magnetic translation), a dynamical operator generated by the usual time-independent Landau Hamiltonian, and a nonadiabatic operator that determines the transition probabilities among the Landau levels. Since the path-ordered magnetic translation and the nonadiabatic operators are, up to completely determined numerical phase factors, just ordinary exponentials whose exponents are explicitly expressible in terms of the canonical variables, all of the factors in the factorization are explicitly constructed. The numerical phase factors are quantum mechanical in nature and could be of significance in interference experiments. The factorization is unique from the point of view of the quantum adiabatic theorem and provides a demonstration of how the quantum adiabatic theorem (incorporating the Berry phase phenomenon) is realized when infinitely degenerate energy levels are involved. Since the factorization separates the effect caused by the electric field into a geometric factor and a nonadiabatic factor, it makes possible to calculate the nonadiabatic transition probabilities near the adiabatic limit. A formula for matrix elements that determines the mixing of the Landau levels for a general, non-adiabatic evolution is also provided by the factorization.