Algebraic Exact Solution for Driven Landau Levels in Two-dimensional Electron Gases

TL;DR

This paper introduces an algebraic, gauge-independent exact solution for driven Landau levels in 2DEGs under arbitrary time-dependent fields, providing new insights into their quantum dynamics and energy absorption behaviors.

Contribution

We develop a novel algebraic method to solve driven Landau levels exactly, independent of gauge or representation, and analyze their Floquet states, quasienergies, and energy absorption.

Findings

Derived exact Floquet states and quasienergies for driven Landau levels.

Identified unbounded wavefunction spreading in resonant driving regimes.

Revealed quantum interference effects influence energy absorption rates.

Abstract

Controlling quantum systems with time-dependent fields opens avenues for engineering novel states of matter and exploring non-equilibrium phenomena. Landau levels in two-dimensional electron gases (2DEGs), with their discrete energy spectrum and characteristic cyclotron dynamics, provide an important platform for realizing and studying such driven quantum systems. While exact solutions for driven Landau levels exist, they have been limited to specific gauges or representations. In this work, we present an algebraic, gauge- and representation-independent exact solution for driven Landau levels in 2DEGs subject to arbitrary time-dependent electromagnetic fields. Our approach, based on a time-dependent unitary transformation via the displacement operator, provides clear physical insights into the driven quantum dynamics. We apply this method to derive the exact Floquet states and quasienergies for periodically driven Landau levels, and we extend our analysis to the resonant driving regime, where the Floquet picture breaks down and the electron wavefunction exhibits unbounded spatial spreading. Furthermore, we calculate the instantaneous energy absorption rate, revealing distinct absorption behaviors between coherent states and Fock or thermal states, stemming from quantum interference effects.