Local electrical tuning of the nonlocal signals in a Cooper pair splitter

TL;DR

This paper demonstrates how local electrical tuning in a Cooper pair splitter device can control the balance between positive and negative conductance correlations, optimizing quantum transport processes.

Contribution

It introduces a gate-tunable device enabling spatially resolved control of quantum dot couplings, revealing transitions between different conductance correlation regimes.

Findings

Gate-induced transitions between positive and negative conductance correlations.

Experimental validation of in-situ electrical tuning of quantum transport.

Modeling shows control over Cooper pair splitting and local processes.

Abstract

A Cooper pair splitter consists of a central superconducting contact, S, from which electrons are injected into two parallel, spatially separated quantum dots (QDs). This geometry and electron interactions can lead to correlated electrical currents due to the spatial separation of spin-singlet Cooper pairs from S. We present experiments on such a device with a series of bottom gates, which allows for spatially resolved tuning of the tunnel couplings between the QDs and the electrical contacts and between the QDs. Our main findings are gate-induced transitions between positive conductance correlation in the QDs due to Cooper pair splitting and negative correlations due to QD dynamics. Using a semi-classical rate equation model we show that the experimental findings are consistent with in-situ electrical tuning of the local and nonlocal quantum transport processes. In particular, we illustrate how the competition between Cooper pair splitting and local processes can be optimized in such hybrid nanostructures.