Higgs-Mediated Optical Amplification in a Nonequilibrium Superconductor

We propose a novel nonequilibrium phenomenon, through which a prompt quench from a metal to a transient superconducting state can induce large oscillations of the order parameter amplitude. We argue that this oscillating mode acts as a source of parametric amplification of the incident radiation. We report experimental results on optically driven K3C60 that are consistent with these predictions. The effect is found to disappear when the onset of the excitation becomes slower than the Higgs-mode period, consistent with the theory proposed here. These results open new possibilities for the use of collective modes in many-body systems to induce nonlinear optical effects.

Automated summary

The study introduces a novel nonequilibrium phenomenon where a prompt quench from a metal to a transient superconducting state induces large oscillations of the order parameter amplitude. The oscillating mode is suggested to act as a source of parametric amplification of the incident radiation, with experimental results on optically driven K3C60 supporting these predictions. The effect diminishes when the excitation onset surpasses the Higgs-mode period, presenting new possibilities for inducing nonlinear optical effects using collective modes in many-body systems.