A model for the microwave assisted magnetoresistance oscillations in a 2D electron system

Abstract

In this work we present a model for the photoconductivity of a two dimensional electron system (2DES) subjected to a magnetic field. The model includes the microwave and Landau contributions in a nonperturbative exact way, Impurity scattering effects are treated perturbatively. Based on this formalism, we provide a Kubo-like formula that takes into account the oscillatory Floquet structure of the problem. We discuss results related with the recently discovered zero-resistance states. It is found that, in agreement with experiment, negative dissipation can only be induced in very high mobility samples.

Photoconductivity in AC-driven modulated two-dimensional electron gas in a perpendicular magnetic field

“…where the definition f µν = f (E µ ) − f (E ν ) was used. The expectation value for the momentum operator is explicitly computed with the help of equations ( 8), (18), and ( 23), retaining terms linear in the modulation potential, and after a lengthy calculation it yields…”

“…., δ = 1 2 [1,2], or δ = 1 4 [3,4]. These discoveries triggered a large number of experimental [5][6][7][8][9] and theoretical [10][11][12][13][14][15][16][17][18][19][20][21] studies. According to [13], ZRSs probably originate from negative resistance states (NRSs); it was argued that negative resistance induces the formation of current domains, yielding an instability that drives the system into a ZRS.…”

“…The existence of NRSs was first predicted in the pioneering work of Ryzhii [10,11]. Nowadays, two distinct mechanisms that produce negative longitudinal conductance are known: (i) the impurity scattering mechanism, which is caused by the disorder assisted absorption and emission of microwaves [10][11][12][13][14][15][16][17][18], and (ii) the distribution function mechanism, according to which the microwave absorption modifies the electron distribution function, leading to a negative longitudinal conductance [5,[19][20][21]. A model for the impurity scattering mechanism was proposed previously by the authors [17,18]; the model is based on the fact that the microwave and Landau dynamics can be exactly taken into account, producing well defined Floquet-Landau states.…”

“…(i) The study of both weak [22] and strong [23] periodically modulated 2DESs in the presence of magnetic fields has led to the discovery of interesting transport effects, such as commensurability phenomena and transport anisotropies. (ii) The theoretical method previously developed in [17,18] is well suited to study this kind of system. (iii) The use of artificially fabricated arrays of periodic scatterers at the interface of ultraclean GaAs/Al x Ga 1−x As heterostructures [22][23][24][25] may allow us to test the predictions made by these theoretical studies.…”

“…The magnetoresistance exhibits giant oscillations, periodic in ǫ = ω/ω c with ω the radiation frequency and ω c the cyclotron frequency; the series of minima formed at ǫ = j + δ, j = 1, 2, 3...., δ = 1 2 [1,2], or δ = 1 4 [3,4]. These discoveries triggered a large number of experimental [5,6,7,8,9] and theoretical [10,11,12,13,14,15,16,17,18,19,20,21] studies. According to reference [13], ZRS probably originate from negative resistance states (NRS); it was argued that negative resistance induces the formation of current domains, yielding an instability that drives the system into a ZRS.…”