Dynamical quantum phase transitions in a mesoscopic superconducting system

TL;DR

This paper investigates dynamical quantum phase transitions in a mesoscopic superconducting system with a quantum dot, revealing non-analytic behavior in the system's response to quenches, which could be experimentally detected via charge tunneling spectroscopy.

Contribution

It demonstrates the occurrence of dynamical quantum phase transitions in a superconducting quantum dot system using time-dependent numerical renormalization group methods, linking theory with experimental detection.

Findings

Identification of non-analytic features in the return rate during quenches.

Observation of a dynamical singlet-doublet phase transition.

Feasibility of detecting transitions via charge tunneling spectroscopy.

Abstract

We inspect signatures of dynamical quantum phase transitions driven by two types of quenches acting on a correlated quantum dot embedded between superconducting and metallic reservoirs. Under stationary conditions the proximity induced on-dot pairing combined with the strong Coulomb repulsion prefers the quantum dot to be either in the singly occupied (spinful) or BCS-type (spinless) ground state configuration. We study the time evolution upon traversing such a phase boundary due to quantum quenches by means of the time-dependent numerical renormalization group approach, revealing non-analytic features in the low-energy return rate. Quench protocols can be realized in a controllable manner and we are confident that detection of this dynamical singlet-doublet phase transition would be feasible by the charge tunnelling spectroscopy.