Dynamical phases transitions in periodically driven Bardeen-Cooper-Schrieffer systems

TL;DR

This paper systematically explores the dynamical phase diagram of a periodically driven BCS superconductor, identifying four distinct phases and demonstrating robustness across different driving mechanisms through a classical oscillator analogy.

Contribution

It introduces a comprehensive analysis of dynamical phases in driven BCS systems, including the identification of new phases and the mapping to classical oscillators.

Findings

Identification of four dynamical phases: Rabi-Higgs, gapless, synchronized Higgs, and time-crystal.

Demonstration of robustness of phase features across different driving protocols.

Mapping of the BCS problem to classical oscillators to explain phase origins.

Abstract

We present a systematic study of the dynamical phase diagram of a periodically driven BCS system as a function of drive strength and frequency. Three different driving mechanism are considered and compared: oscillating density of states, oscillating pairing interaction and oscillating external paring field. We identify the locus in parameter space of parametric resonances and four dynamical phases: Rabi-Higgs, gapless, synchronized Higgs and time-crystal. We demonstrate that the main features of the phase diagram are quite robust to different driving protocols and discuss the order of the transitions. By mapping the BCS problem to a collection of nonlinear and interacting classical oscillators, we shed light on the origin of time-crsytalline phases and parametric resonances appearing for subgap excitations.