Phase and periodicity of Aharonov-Bohm oscillations: effect of channel mixing

TL;DR

This paper investigates how a negative delta function impurity in an Aharonov-Bohm ring causes abrupt phase shifts and influences conductance oscillations, revealing conditions for $hc/2e$ periodicity due to evanescent mode coupling.

Contribution

It introduces a new mechanism for conductance oscillations involving negative delta potentials and explains flux periodicity changes through mode coupling effects.

Findings

Abrupt phase changes across quasi bound states caused by negative delta impurities.

Conductance oscillations depend on the strength of the delta potential.

Evanescent mode coupling can induce $hc/2e$ flux periodicity at specific energies.

Abstract

We take a negative delta function impurity in one arm of a quasi one dimensional Aharonov-Bohm ring and demonstrate abrupt phase changes across a quasi bound state of the negative delta function potential. We give a new mechanism for conductance oscillations with the strength of the negative delta potential. We also show that coupling to evanescent modes can result in a $hc/2e$ flux periodicity at certain energies. These observations were made in a recent ingenious experiment by D. Mailly et al [1].