Effect of Landau quantization on linear magnetoresistance of periodically modulated two-dimensional electron gas

TL;DR

This paper theoretically investigates how Landau quantization influences linear magnetoresistance in a periodically modulated two-dimensional electron gas, revealing quantum oscillations that persist at higher temperatures and depend on modulation strength.

Contribution

It provides a comprehensive theoretical framework for understanding quantum oscillations in magnetoresistance due to Landau quantization and periodic potential modulation in 2D electron gases.

Findings

Quantum oscillations with larger periods and smaller amplitudes survive at higher temperatures.

Oscillations are related to the modification of the density of states by the modulation.

Perpendicular resistivity shows oscillations linked to hopping transport and guiding center shifts.

Abstract

The linear response of two-dimensional electron gas in a perpendicular magnetic field in the presence of a spatially dependent classically smooth electrostatic potential is studied theoretically, by application of the Kubo formula for nonlocal conductivity tensor. In the classical transport regime, a general expression for the conductivity tensor through the correlation functions of the homogeneous electron gas is derived. The quantum transport regime, when Landau quantization is essential, is studied for the case of unidirectional periodic potential modulation. Apart from the Shubnikov-de Haas oscillations, the resistivity can demonstrate quantum oscillations with larger periods and smaller amplitudes, which survive when temperature increases. These oscillations exist when the modulation amplitude considerably exceeds the cyclotron energy so the Landau subbands, formed out of the Landau levels by the modulation potential, overlap in the energy domain. Both diagonal components of the resistivity tensor demonstrate oscillations related to modification of the density of states by the modulation. In addition, the resistivity component perpendicular to the modulation axis, which is caused by the scattering-assisted hopping transport, shows another kind of oscillations related to enhancement of the hopping probability when the guiding center of cyclotron orbit shifts by the doubled cyclotron radius. It is suggested that such high-temperature oscillations can be detected under conditions when the modulation period considerably exceeds the cyclotron radius.