Light-amplified Landau-Zener conductivity in gapped graphene monolayers: a simulacrum of photo-catalyzed vacuum instability

Abstract

Interband transitions of electrons in a gapped graphene monolayer are highly stimulated near the Fermi surface when a high-frequency electric wave of weak intensity and a strong constant electric field are superposed on its surface. We consider the situation in which the photon energy associated with the fast-oscillating field is slightly below the graphene gap so that the quantum transitions still occur through tunneling effects while being facilitated by multiphoton absorption channels. In the considered parameter regime the photo-catalyzed current linked to the described setup is shown to exceed the one driven by the strong field solely by several orders of magnitude. Optimization conditions are revealed and an asymptotic formula for the current density is derived. The robustness of our assessment supports the viability of detecting this phenomenon in graphene, which would serve as a first-principle-proof of concept of the dynamically-assisted Schwinger mechanism in QED.Comment: 12 pages, 6 figure