Interference of electrons in backscattering through a quantum point contact

TL;DR

This study uses scanning gate microscopy to explore electron backscattering and interference in a high-mobility 2D electron gas, revealing how magnetic fields and energy levels influence branching patterns and fringe spacing.

Contribution

It provides new insights into the spatial and energetic dependence of electron interference and backscattering in quantum point contacts, highlighting the role of magnetic fields.

Findings

Branches caused by electron backscattering are observed and decorated with interference fringes.

Branch patterns change significantly at the low-energy side of conductance plateaus.

Interference fringe spacing varies by over 50% across microns.

Abstract

Scanning gate microscopy is used to locally investigate electron transport in a high-mobility two-dimensional electron gas formed in a GaAs/AlGaAs heterostructure. Using quantum point contacts (QPC) we observe branches caused by electron backscattering decorated with interference fringes similar to previous observations by Topinka et al. We investigate the branches at different points of a conductance plateau as well as between plateaus, and demonstrate that the most dramatic changes in branch pattern occur at the low-energy side of the conductance plateaus. The branches disappear at magnetic fields as low as 50 mT demonstrating the importance of backscattering for the observation of the branching effect. The spacing between the interference fringes varies by more than 50% for different branches across scales of microns. Several scenarios are discussed to explain this observation.