Out-of-equilibrium criticalities in graphene superlattices

In thermodynamic equilibrium, current in metallic systems is carried by electronic states near the Fermi energy, whereas the filled bands underneath contribute little to conduction. Here, we describe a very different regime in which carrier distribution in graphene and its superlattices is shifted so far from equilibrium that the filled bands start playing an essential role, leading to a critical-current behavior. The criticalities develop upon the velocity of electron flow reaching the Fermi velocity. Key signatures of the out-of-equilibrium state are current-voltage characteristics that resemble those of superconductors, sharp peaks in differential resistance, sign reversal of the Hall effect, and a marked anomaly caused by the Schwinger-like production of hot electron-hole plasma. The observed behavior is expected to be common to all graphene-based superlattices.

Automated summary

In the out-of-equilibrium state, the carrier distribution in graphene and its superlattices is shifted away from equilibrium, leading to a critical-current behavior where the filled bands play a crucial role. The characteristics of this state include current-voltage characteristics similar to superconductors, sharp peaks in differential resistance, sign reversal of the Hall effect, and an anomaly caused by the production of hot electron-hole plasma similar to the Schwinger effect. This behavior is expected to be common in all graphene-based superlattices.