Hanbury Brown Twiss effects in channel mixing normal-superconducting systems

TL;DR

This paper explores how the proximity effect influences current cross correlations in multiterminal normal-superconducting systems, revealing conditions under which correlations switch from positive to negative, with implications for quantum transport understanding.

Contribution

It introduces an experimental setup analogous to optical Hanbury Brown Twiss experiments to study proximity effects in quantum dots with normal and superconducting reservoirs.

Findings

Proximity effect can reverse cross correlation sign with magnetic flux.

Cross correlations are positive when coupling to normal reservoirs dominates.

Particle counting explains correlations in weak proximity regime.

Abstract

An investigation of the role of the proximity effect in current cross correlations in multiterminal, channel-mixing, normal-superconducting systems is presented. The proposed experiment is an electrical analog of the optical Hanbury Brown Twiss intensity cross correlation experiment. A chaotic quantum dot is connected via quantum point contacts to two normal and one superconducting reservoir. For dominating coupling of the dot to the superconducting reservoir, a magnetic flux of the order of a flux quantum in the dot suppresses the proximity effect and reverses the sign of the cross correlations, from positive to negative. In the opposite limit, for a dominating coupling to the normal reservoirs, the proximity effect is weak and the cross correlation are positive for a nonideal contact between the dot and the superconducting reservoir. We show that in this limit the correlations can be explained with particle counting arguments.