Magnetoresistance oscillations in high-mobility two-dimensional semiconductors: A unified description with balance-equation model

This article gives a brief introduction to the magnetoresistance oscillations in high-mobility two-dimensional semiconductors at low temperatures, which are induced by a microwave radiation, a dc current, a branch of acoustic phonons, or a combination of them, and a comprehensive review of a balance-equation model for nonlinear magnetotransport in systems with short thermalization time, which enables a unified description for all these magnetoresistance oscillations. The appearance of these magnetoresistance oscillations is referred to an additional average energy Δɛ obtained (or released) by an electron during its transition between different states due to impurity and phonon-assisted scatterings. This energy provided by a microwave photon of frequency ωω (Δɛ=ω), by a dc current of density J=NsevJ=Nsev (Δɛ≈ωj=2kFv with vv the drift velocity, kFkF the Fermi wavevector and NsNs the sheet density of 2D electrons), by an acoustic phonon of wavevector 2kF2kF having velocity vsvs (Δɛ≈ωs=2kFvs), or by a combination of them, results in a frequency shift ωω, ωjωj, ωsωs, or, e.g., ω+ωj−ωsω+ωj−ωs, in the periodic electron-density-correlation function Π2(q||,Ω) of the 2D system in a magnetic field. When the frequency shift varies by an amount of cyclotron frequency ωcωc the magnetoresistivity and other transport quantities experience a change of one oscillation period, suggesting parameter ϵω≡ω/ωcϵω≡ω/ωc, ϵj≡ωj/ωcϵj≡ωj/ωc, ϵs≡ωs/ωcϵs≡ωs/ωc, or ϵω+ϵj−ϵsϵω+ϵj−ϵs, to control the corresponding oscillation. Thus achieves a unified picture of microwave-, dc current-, acoustic phonon-, and their combination-induced magnetoresistance oscillations. The balance-equation model not only reproduces the main features of all these magnetoresistance oscillations, but also explains many other prominent experimental observations.