Higgs-Mediated Optical Amplification in a Nonequilibrium Superconductor
M. Buzzi, Gregor Jotzu, A. Cavalleri, J. I. Cirac, Eugene Demler, Bertrand I. Halperin, Mikhail D. Lukin, Tao Shi, Yao Wang, Daniel K. Podolsky
Abstract
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 K 3 C 60 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.