Aharonov-Bohm effect in the presence of evanescent modes

TL;DR

This paper investigates how impurities affect the Aharonov-Bohm effect in mesoscopic loops with evanescent modes, revealing conditions for large negative magnetoconductance changes relevant for quantum switching.

Contribution

It introduces a theoretical analysis of impurity effects on magnetoconductance in loops with evanescent modes, highlighting conditions for significant negative responses.

Findings

Impurities without resonant states lead to large negative magnetoconductance.

Evanescent modes produce negative magnetoconductance regardless of impurities.

Impurity effects depend on the creation of resonant states in the system.

Abstract

It is known that differential magnetoconductance of a normal metal loop connected to reservoirs by ideal wires is always negative when an electron travels as an evanescent modes in the loop. This is in contrast to the fact that the magnetoconductance for propagating modes is very sensitive to small changes in geometric details and the Fermi energy and moreover it can be positive as well as negative. Here we explore the role of impurities in the leads in determining the magnetoconductance of the loop. We find that the change in magnetoconductance is negative and can be made large provided the impurities do not create resonant states in the systems. This theoretical finding may play an useful role in quantum switch operations.