Single-particle relaxation time in a spatially fluctuating magnetic field

Abstract

We study Shubnikov de Haas ͑SdH͒ oscillations in a nonplanar stripe-shaped two-dimensional electron gas ͑2DEG͒. The effective-field normal to the nonplanar 2DEG is spatially modulated, when uniform external magnetic field is applied. We find that the amplitude of the SdH oscillations dramatically drops in the tilted magnetic field. From the Dingle plot of SdH oscillations we extract single-particle relaxation time. Reduction of this time in the tilted field, which leads to the enhanced damping of SdH oscillations, is shown to be due to the scattering of the electron by magnetic-field fluctuations. We calculate quantum lifetime of the electron in a tilted magnetic field. The agreement between these calculations and experimental result is found. In order to explain the damping of the SdH oscillations for magnetic field BϾ1 T we also take into account the spatial variation of the Landau filling factor.

Negative linear classical magnetoresistance in a corrugated two-dimensional electron gas

“…7,8 Due to the presence of interfacial roughness, electrons in such structures see an external uniform in-plane magnetic field B ʈ as a random perpendicular magnetic field B rand Ќ . 9 The presence of an additional small uniform perpendicular field leads to the negative MR in accordance with theoretical predictions. 5,6 Another theoretical approach beyond the Boltzmann approximation is associated with so-called memory effects in electronic transport.…”

“…9,16 In these works, the regrowth processes resulted in regular stripes with a well defined periodicity along or across the Hall device channel (contrary to the present samples characterized by a shorter lattice period), and magnetotransport experiments were mainly focused on the study of the electron dynamics when the magnetic field is oriented parallel or tilted in relation to the sample substrate. In the samples of the present work, the magnetic field is oriented strictly perpendicular to the sample surface and also to the current direction.…”

“…The distance between voltage probes was 100 m and the width of the current channel is 50 m. We followed a preparation process similar to that described in Ref. 9. In a different way than samples presented in Refs.…”

Quasiclassical negative magnetoresistance of a two-dimensional electron gas in a random magnetic field

“…The mobility of the nonplanar 2DEG is (40Ϫ50)ϫ10 3 cm 2 /V s, and the electron density is n s ϭ5.5ϫ10 11 cm Ϫ2 at Tϭ4.2 K. The mobility in samples studied here is smaller than in the previously investigated structures. 11,12,14 We attribute this fact to the scattering by the interface roughness, which is consistent with the more irregular character of the surface in these samples. The mean free path at Bϭ0l 0 is 0.8 m, which is comparable with the correlation length of the random magnetic field.…”

“…Depending on the substrate etching and the GaAs buffer layer thickness it is possible to obtain variety of the surface configurations between ''stripelike'' and ''hilllike'' structures. 11,12,14 However, this method does not permit to grow samples with an absolutely isotropic structured surface due to the orientation-dependent properties of the GaAs material. We compare the profile of the effective magnetic field with the correlator, which is usually used in different theories describing transport properties of 2D electrons in a random magnetic field: 4,6 F͑r ͒Ϸ͗B͑ 0 ͒B͑ r ͒͘ϷB 0 2 /͑1ϩr 2 /4 2 ͒ 3/2 .…”