Experimental signature of transient symmetry breaking in a cavity superconductor

TL;DR

This study demonstrates that intense terahertz pulses can induce transient symmetry breaking in a cavity superconductor, revealing new non-equilibrium states with unique nonlinear responses detectable via time-resolved spectroscopy.

Contribution

It provides experimental evidence of transient symmetry breaking in a cavity superconductor using ultrafast terahertz spectroscopy, highlighting the role of strong light-matter coupling.

Findings

Transient supercurrents modify electronic symmetries.

High-order nonlinear responses indicate symmetry breaking.

Cavity coupling enhances detection sensitivity.

Abstract

Transient states of matter far from equilibrium may exhibit physical properties beyond those allowed by the equilibrium-state crystalline symmetries. We explore ultrafast and direct electronic excitations of transient states in a cavity superconductor by using time-resolved terahertz-pump terahertz-probe spectroscopy. Our results show that the strong terahertz field can transiently modify the symmetries of the electronic subsystems via the injection of a transient supercurrent, leading to high-order nonlinear dynamical responses that are not compatible with the equilibrium-state symmetries, which evidences for transient symmetry breaking on the picosecond time scale. Our study also finds that the strong coupling of the superconductor to the designed microcavities enables the sensitive detection of the nonlinear responses associated to the transient symmetry breaking.