How branching can change the conductance of ballistic semiconductor devices

TL;DR

This paper shows how electron flow branching in semiconductor nanostructures can significantly alter transport properties, affecting magnetoresistance peaks even in small systems with minimal disorder.

Contribution

It introduces a model incorporating disorder potential to explain peak splitting in magnetoresistance due to electron flow branching.

Findings

Branching causes splitting of commensurability peaks.

Disorder potential influences the shape of peak splitting.

Magnetic focusing peaks remain largely unaffected.

Abstract

We demonstrate that branching of the electron flow in semiconductor nanostructures can strongly affect macroscopic transport quantities and can significantly change their dependence on external parameters compared to the ideal ballistic case even when the system size is much smaller than the mean free path. In a corner-shaped ballistic device based on a GaAs/AlGaAs two-dimensional electron gas we observe a splitting of the commensurability peaks in the magnetoresistance curve. We show that a model which includes a random disorder potential of the two-dimensional electron gas can account for the random splitting of the peaks that result from the collimation of the electron beam. The shape of the splitting depends on the particular realization of the disorder potential. At the same time magnetic focusing peaks are largely unaffected by the disorder potential.