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

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

2006-04-07

arxiv.org/abs/cond-mat/0604214v1

J. Phys.: Condens. Matter 18 (2006) 4029-4045

Physics

Condensed Matter

Mesoscale and Nanoscale Physics

20 pages, 8 figures

Scientific paper

10.1088/0953-8984/18/16/010

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 $\epsilon = \omega / \omega_c$ with $\omega$ the radiation frequency and $\omega_c$ the cyclotron frequency. The oscillations follow a pattern with minima centered at $\omega/\omega_c =j + {1/2} (l-1) + \delta $, and maxima centered at $\omega/\omega_c =j + {1/2} (l-1) - \delta $, where $j=1,2,3.......$, $\delta \sim 1/5$ is a constant shift and $l$ is the dominant multipole contribution. Negative resistance states (NRS) develop as the electron mobility and the intensity of the microwave power are increased. These NRS appear in a narrow window region of values of the lattice parameter ($a$), around $a \sim l_B$, 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 $GaAs/Al_xGa_{1-x} As$ heterostructures.

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