Emergence and Manipulation of non-equilibrium Yu-Shiba-Rusinov states

TL;DR

This paper explores how time-dependent manipulations of magnetic impurities in superconductors can induce quantum phase transitions and alter Yu-Shiba-Rusinov states, providing insights into non-equilibrium quantum phenomena.

Contribution

It demonstrates the control and visualization of non-equilibrium Yu-Shiba-Rusinov states through time-dependent magnetic perturbations and differential conductance measurements.

Findings

Time-dependent magnetic changes induce quantum phase transitions.

Differential conductance images non-equilibrium local density of states.

System transitions from singlet to doublet ground state.

Abstract

The experimental advances in the study of time-dependent phenomena has opened a new path to investigating the complex electronic structure of strongly correlated and topological materials. Yu-Shiba-Rusinov (YSR) states induced by magnetic impurities in $s$-wave superconductors provide an ideal candidate system to study the response of a system to time-dependent manipulations of the magnetic environment. Here, we show that by imposing a time-dependent change in the magnetic exchange coupling, by changing the relative alignment of magnetic moments in an impurity dimer, or through a periodic drive of the impurity moment, one can tune the system through a time-dependent quantum phase transition, in which the system undergoes a transition from a singlet to a doublet ground state. We show that the electronic response of the system to external perturbations can be imaged through the time-dependent differential conductance, $dI(t)/dV$, which, in analogy to the equilibrium case, is proportional to a non-equilibrium local density of states. Our results open the path to visualizing the response of complex quantum systems to time-dependent external perturbations.