Conductance Anomaly in a Partially Open Adiabatic Quantum Point Contact

TL;DR

This paper explains conductance anomalies in adiabatic quantum point contacts caused by electron interactions and backscattering, leading to conductance reduction and oscillations influenced by magnetic fields.

Contribution

It introduces a universal interaction-based mechanism for conductance anomalies in partially open quantum channels, aligning with experimental observations.

Findings

Backscattering induces Friedel oscillations affecting conductance.

Magnetic fields cause conductance oscillations and non-monotonic anomaly behavior.

Interaction effects modify conductance in a universal manner.

Abstract

We demonstrate that conductance anomalies can arise in a clean, adiabatic quantum point contact when a channel is partially transmitting. Even for a smooth barrier potential, backscattering induces Friedel oscillations that, via electron interactions, generate a singular correction to the conductance. This correction is maximized when the channel is half-open, resulting in a reduction of conductance. In addition, a magnetic field applied perpendicular to the spin-orbit axis modifies the single-particle spectrum, resulting in conductance oscillations via Fabry-P\'erot-type interference, as well as a non-monotonic field dependence of the anomaly. Our findings reveal a universal mechanism by which interactions modify the conductance of an ideal partially open channel and offer a possible explanation for the anomalous features observed in experiments.