Steady-state dynamics and non-local correlations in thermoelectric Cooper pair splitters

TL;DR

This paper analyzes the nonlocal quantum correlations in thermoelectric Cooper pair splitters, clarifying operating regimes and revealing how contact effects influence resonances and current parity, advancing solid-state quantum entanglement control.

Contribution

It provides a detailed analysis connecting quantum discord with transport signals, identifying nonlocal quantum correlations and effects of contact-induced broadening in Cooper pair splitters.

Findings

Identification of nonlocal quantum correlations via quantum discord.

Contact-induced broadening causes shifted resonances and parity reversal.

Gate voltage control enables manipulation of quantum correlations.

Abstract

Recent experiments on Cooper pair splitters using superconductor-quantum dot hybrids have embarked on creating entanglement in the solid-state, by engineering the sub-gap processes in the superconducting region. Using the thermoelectric Cooper pair splitter setup [Nat. Comm., 12, 21, (2021)] as a prototype, we present a comprehensive analysis of the fundamental components of the observed transport signal, aiming to critically clarify the operating regimes and confirm the nonlocal and nonclassical nature of correlations arising from crossed Andreev processes. By making a nexus with quantum discord, we identify operating points of nonlocal quantum correlations in the CPS device -- information that cannot be extracted from the transport signal alone. A notable consequence of our analysis is the finding that contact-induced level broadening of the quantum dot's discrete energy spectrum, along with its hybridization with the superconducting segment, can lead to shifted resonances in the crossed Andreev process as well as a parity reversal in the thermoelectric current. Our work thereby provides detailed insights into the gate voltage control of the quantum correlations in superconducting-hybrid Cooper pair splitters, revealing new avenues for harnessing quantum correlations in solid-state systems.