Transmission of a microwave cavity coupled to localized Shiba states

TL;DR

This paper explores how microwave cavity measurements can detect localized Shiba states and quantum phase transitions in a strongly correlated quantum dot coupled to superconducting leads.

Contribution

It introduces a method to use photonic transmission to identify Shiba states and quantum phase transitions in such systems, advancing quantum sensing techniques.

Findings

Photonic transmission signals reveal Shiba states.

Quantum phase transition causes a sudden change in transmission.

Numerical renormalization group confirms the results.

Abstract

We consider a strongly correlated quantum dot, tunnel coupled to two superconducting leads and capacitively coupled to a single mode microwave cavity. When the superconducting gap is the largest energy scale, multiple Shiba states are formed inside the gap. The competition of these states for the ground state signals a quantum phase transition. We demonstrate that photonic measurements can be used to probe such localized Shiba states. Moreover, the quantum phase transition can be pinpointed exactly from the sudden change in the transmission signal. Calculations were performed using the numerical renormalization group approach.