Out-of-equilibrium criticalities in graphene superlattices

TL;DR

This paper explores a novel out-of-equilibrium regime in graphene superlattices where filled bands significantly influence conduction, leading to critical-current behaviors and phenomena similar to superconductivity.

Contribution

It introduces the concept of out-of-equilibrium criticalities in graphene superlattices, highlighting the role of filled bands and identifying unique electronic behaviors at high current velocities.

Findings

Current-voltage characteristics resemble superconductors

Sharp peaks in differential resistance observed

Sign reversal of the Hall effect and hot electron-hole plasma production

Abstract

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 resembling 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 for all graphene-based superlattices.