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 Δ ɛ 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 ω ( Δ ɛ = ω ), by a dc current of density J = N s e v ( Δ ɛ ≈ ω j = 2 k F v with v the drift velocity, k F the Fermi wavevector and N s the sheet density of 2D electrons), by an acoustic phonon of wavevector 2 k F having velocity v s ( Δ ɛ ≈ ω s = 2 k F v s ), or by a combination of them, results in a frequency shift ω , ω j , ω s , or, e.g., ω + ω j − ω s , in the periodic electron-density-correlation function Π 2 ( q | | , Ω ) of the 2D system in a magnetic field. When the frequency shift varies by an amount of cyclotron frequency ω c the magnetoresistivity and other transport quantities experience a change of one oscillation period, suggesting parameter ϵ ω ≡ ω / ω c , ϵ j ≡ ω j / ω c , ϵ s ≡ ω s / ω c , or ϵ ω + ϵ j − ϵ s , 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.