Stability of Branched Flow from a Quantum Point Contact

TL;DR

This paper investigates the surprising stability of branched electron flow from a quantum point contact in disordered systems, demonstrating that both classical and quantum models can reproduce this phenomenon, challenging the notion of its purely quantum origin.

Contribution

The study shows that the stability of branched flow is due to the physics of the QPC and can be explained by classical physics, not solely quantum mechanics, providing new insights into electron transport.

Findings

Classical models can reproduce the observed stability of branched flow.

Quantum and classical explanations both account for the stability.

Stability persists despite changes in the QPC eigenmodes.

Abstract

In classically chaotic systems, small differences in initial conditions are exponentially magnified over time. However, it was observed experimentally that the (necessarily quantum) "branched flow" pattern of electron flux from a quantum point contact (QPC) traveling over a random background potential in two-dimensional electron gases(2DEGs) remains substantially invariant to large changes in initial conditions. Since such a potential is classically chaotic and unstable to changes in initial conditions, it was conjectured that the origin of the observed stability is purely quantum mechanical, with no classical analog. In this paper, we show that the observed stability is a result of the physics of the QPC and the nature of the experiment. We show that the same stability can indeed be reproduced classically, or quantum mechanically. In addition, we explore the stability of the branched flow with regards to changes in the eigenmodes of quantum point contact.