Quantum quench dynamics and population inversion in bilayer graphene

TL;DR

This paper investigates the non-equilibrium dynamics of bilayer graphene during a controlled electric field quench, revealing defect formation, population inversion, and potential applications in tunable infrared radiation sources.

Contribution

It introduces a coupled non-linear Landau-Zener model for bilayer graphene dynamics and demonstrates agreement with Kibble-Zurek theory, highlighting population inversion phenomena.

Findings

Defect density matches Kibble-Zurek predictions with logarithmic corrections.

Population inversion occurs near the Dirac point after the quench.

Similar dynamics observed in cold atoms with quadratic band crossing.

Abstract

The gap in bilayer graphene (BLG) can directly be controlled by a perpendicular electric field. By tuning the field through zero at a finite rate in neutral BLG, excited states are produced. Due to screening, the resulting dynamics is determined by coupled non-linear Landau-Zener models. The generated defect density agrees with Kibble-Zurek theory in the presence of subleading logarithmic corrections. After the quench, population inversion occurs for wavevectors close to the Dirac point. This could, at least in principle provide a coherent source of infra-red radiation with tunable spectral properties (frequency and broadening). Cold atoms with quadratic band crossing exhibit the same dynamics.