A classical model for the negative dc conductivity of ac-driven 2D electrons near the cyclotron resonance

TL;DR

This paper presents a classical model explaining how weak nonparabolicity in 2D electrons under strong irradiation near cyclotron resonance can cause negative dc conductivity, depending on field orientations and frequency detuning.

Contribution

It introduces a classical approach showing how weak nonparabolicity influences dc conductivity, revealing conditions for negative conductivity near cyclotron resonance.

Findings

Weak nonparabolicity can induce negative dc conductivity.

The sign of conductivity depends on field orientation and frequency detuning.

Hall conductivity remains largely unaffected.

Abstract

A classical model for {\em dc} transport of two dimensional electrons in a perpendicular magnetic field and under strong irradiation is considered. We demonstrate that, near the cyclotron resonance condition, and for {\em linear} polarization of the {\em ac} field, a strong change of the diagonal component, $\sigma_d$, of the {\em dc} conductivity occurs in the presence of a {\em weak} nonparabolicity of the electron spectrum. Small change in the electron effective mass due to irradiation can lead to negative $\sigma_d$, while the Hall component of the {\em dc} conductivity remains practically unchanged. Within the model considered, the sign of $\sigma_d$ depends on the relative orientation of the {\em dc} and {\em ac} fields, the sign of the detuning of the {\em ac} frequency from the cyclotron resonance, and the sign of nonparabolic term in the energy spectrum.