Non-equilibrium electron crystals

We explore a new crystal-like non-equilibrium state of the Coulomb interacting electron gas. This state shares some similarities with the Faraday instability of classical liquids and can be created by parametrically exciting plasmons using a coherent Floquet drive with a slowly oscillating amplitude. We discuss the emergent collective modes that form as excitations on top of the time-periodic crystal-like state steady state. Possible applications include powerful plasmon sources and plasmonic time-reversal mirrors.