Symmetry causes a huge conductance peak in double quantum dots

TL;DR

This paper predicts a significant interference effect in double quantum dots with mirror symmetry, where constructive interference can greatly enhance conductance, and this effect is sensitive to magnetic fields, enabling a new type of magnetic field detector.

Contribution

The paper introduces a novel interference phenomenon in symmetric double quantum dots that dramatically increases conductance, surpassing known quantum fluctuation effects.

Findings

Constructive interference can make a tunnel barrier transparent.

The effect is orders of magnitude larger than universal conductance fluctuations.

A small magnetic field can suppress the effect, enabling magnetic field detection.

Abstract

We predict a huge interference effect contributing to the conductance through large ultra-clean quantum dots of chaotic shape. When a double-dot structure is made such that the dots are the mirror-image of each other, constructive interference can make a tunnel barrier located on the symmetry axis effectively transparent. We show (via theoretical analysis and numerical simulation) that this effect can be orders of magnitude larger than the well-known universal conductance fluctuations and weak-localization (both less than a conductance quantum). A small magnetic field destroys the effect, massively reducing the double-dot conductance; thus a magnetic field detector is obtained, with a similar sensitivity to a SQUID, but requiring no superconductors.