Higgs amplification in non-equilibrium K3C60

The quest for new functionalities in quantum materials has recently been extended to non-equilibrium states. In the context of superconductivity, examples have included the generation of transient superconductivity above the thermodynamic transition temperature, the excitation of coherent Higgs-mode oscillations, and the optical control of the interlayer phase in the cuprates. In this talk, I will propose that a prompt quench into a transient superconducting state from a metal induces large Higgs fluctuations in the order parameter, and will demonstrate that these fluctuations give rise to the amplification of light at frequencies below the superconducting gap.  I will show new measurements on K₃C₆₀, in which these predictions are verified experimentally