Fig. 1: Summary of the main results.
From: Periodic dynamics in superconductors induced by an impulsive optical quench
a The two building blocks of the effective description of non-equilibrium superconductors are the order parameter and the electromagnetic field in the sample, and the two entities are coupled. Upon photoexcitation, the electromagnetic field displays periodic fluctuation evolution, even if the order parameter dynamics is overdamped. b, c Schematic spectra of plasmons, which are gapped due to the Anderson-Higgs mechanism. Prior to photoexcitation (b), the plasmon distribution function is thermal; the thin blue curve captures the low occupation numbers. After photoexcitation (c), these plasmons proliferate (shown by the thick red-orange curve) through the creation of momentum-conserving pairs. d, e Schematics of time evolution of the electric field in the sample, which always has a zero expectation value. In equilibrium (d), the electric field has a non-zero thermal variance \({\langle {{{{{{{{\boldsymbol{E}}}}}}}}}^{2}\rangle }_{eq}\). After an impulsive optical quench (e), this variance becomes periodically modulated, with the frequency 2ωp being twice the plasmon gap.
