Bernstein modes and giant microwave response of two-dimensional electron system

TL;DR

This paper investigates how virtual Bernstein modes influence the microwave response of a 2D electron system in a magnetic field, revealing enhanced radiation effects and plasma instabilities that explain giant photoresistivity spikes.

Contribution

It introduces the role of virtual Bernstein modes in microwave response and their connection to plasma instability and giant photoresistivity in 2D electron systems.

Findings

Enhanced radiation field in Bernstein mode gaps

Observation of parametric cyclotron resonance

Link to plasma instability and giant photoresistivity spikes

Abstract

We report on a new contribution to the microwave response of a two-dimensional electron system in magnetic field which originates from excitation of virtual Bernstein modes. These collective modes emerge as a result of interaction between usual magnetoplasmon mode and cyclotron resonance harmonics. The electrons are found to experience a strongly enhanced radiation field when its frequency falls in a gap of the Bernstein modes spectrum. This field can give rise to nonlinear effects, one of which, the parametric cyclotron resonance, is discussed. We argue that this resonance leads to a plasma instability in the ultraclean system. The instability-induced heating is responsible for the giant photoresistivity spike recently observed in the vicinity of the 2nd cyclotron resonance harmonic.