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

Abstract

In this work we study the microwave photoconductivity of a two-dimensional electron system (2DES) in the presence of a magnetic field and a two-dimensional modulation (2D). The model includes the microwave and Landau contributions in a non-perturbative exact way; the periodic potential is treated perturbatively. The Landau-Floquet states provide a convenient base with respect to which the lattice potential becomes time dependent, inducing transitions between the Landau-Floquet levels. Based on this formalism, we provide a Kubo-like formula that takes into account the oscillatory Floquet structure of the problem. The total longitudinal conductivity and resistivity exhibit strong oscillations, determined by ϵ = ω/ω(c), with ω the radiation frequency and ω(c) the cyclotron frequency. The oscillations follow a pattern with minima centred at [Formula: see text], and maxima centred at [Formula: see text], where j = 1,2,3..., δ∼1/5 is a constant shift and l is the dominant multipole contribution. Negative resistance states (NRSs) develop as the electron mobility and the intensity of the microwave power are increased. These NRSs appear in a narrow window region of values of the lattice parameter (a), around a∼l(B), where l(B) is the magnetic length. It is proposed that these phenomena may be observed in artificially fabricated arrays of periodic scatterers at the interface of ultraclean GaAs /Al(x)Ga(1-x)As heterostructures.

Nonlinear current of strongly irradiated quantum Hall gas

“…It has long been appreciated that strong radiation effects on the clean Landau levels are tractable using a Floquet transformation. 14,17 However, writing down an explicit Floquet transformation for a disordered Hamiltonian is, in general, intractable. Here, we make progress by exploiting the commutation between Landau and guiding center operators.…”

Investigation of the Hall Effect in Rectangular Quantum Wells With a Perpendicular Magnetic Field in the Presence of a High-Frequency Electromagnetic Wave

“…[30][31][32] The oscillations in Figs. 5 and 6 are known to be the MR oscillations induced by an ac field (microwave-induced resistance oscillations) which were discovered by Zudov et al 33 and have been studied in detail both theoretically 34,35 and experimentally. [30][31][32] The period of these oscillations is known to be determined by the ratio of the EMW frequency, Ω, to the cyclotron frequency, ω c .…”

Microwave induced negative resistance states in 2D electron gas with periodic modulation

“…The longitudinal and Hall conductivities are separated in a dark and microwave induced contributions [9]. Here we quote the result for the microwave induced longitudinal photoconductivity…”

“…Nowadays two distinct mechanisms that produce negative longitudinal resistance are known: (i) the impurity scattering mechanism [4,5] and (ii) the inversion population mechanism [6]. Although the experiments described above do not include the effect of periodical potential modulations, exploring its physical consequences is worthwhile, see the references [7,8] and [9]. In this work we make a theoretical study of the microwave photoconductivity of a 2DES in the presence of a magnetic field and a two-dimensional modulation.…”

“…The explicit expressions for the matrix element of these operators in the Landau-Floquet base appear in detail in references [5,9].…”