Dephasing time and magnetoresistance of two-dimensional electron gas in spatially modulated magnetic fields

TL;DR

This paper investigates how spatially modulated magnetic fields influence weak localization, dephasing times, and magnetoresistance in two-dimensional electron gases, revealing complex behaviors and potential for positive magnetoresistance effects.

Contribution

It provides a detailed analysis of dephasing and magnetoresistance under spatially varying magnetic fields, including new scaling laws and the prediction of a resistance peak at specific field values.

Findings

Dephasing rate scales as H_0^2 d^2 for small field profiles.

Crossover to linear dependence of dephasing rate on H_0 occurs at larger flux values.

Positive magnetoresistance and a resistance peak at H ~ H_0 are predicted.

Abstract

The effect of a spatially modulated magnetic field on the weak localization phenomenon in two-dimensional electron gas (2DEG) is studied. Both the dephasing time $\tau_H$ and magnetoresistance are shown to reveal a nontrivial behavior as functions of the characteristics of magnetic field profiles. The magnetic field profiles with rather small spatial scales $d$ and modulation amplitudes $H_0$ such that $H_0d^2\ll\hbar c/e$ are characterized by the dephasing rate $\tau_H^{-1}\propto H_0^2d^2$. The increase in the flux value $H_0d^2$ results in a crossover to a standard linear dependence $\tau_H^{-1}\propto H_0$. Applying an external homogeneous magnetic field $H$ one can vary the local dephasing time in the system and affect the resulting average transport characteristics. We have investigated the dependence of the average resistance vs the field $H$ for some generic systems and predict a possibility to observe a positive magnetoresistance at not too large $H$ values. The resulting dependence of the resistance vs $H$ should reveal a peak at the field values $H\sim H_0$.