Low-Field Metal-Insulator Transition in AB-Stacked Bilayer Graphene

TL;DR

This study reveals that trigonal warping effects in AB-stacked bilayer graphene enable an insulator-metal transition at significantly lower magnetic fields than previously thought, with potential implications for electronic device control.

Contribution

The paper extends prior analysis by including trigonal warping effects, showing they facilitate a low-field insulator-metal transition in bilayer graphene.

Findings

Trigonal warping causes a fine splitting of Dirac cones.

A small transverse electric field reopens the insulating gap.

The IM transition occurs at magnetic fields around 10 T, much lower than earlier predictions.

Abstract

We investigate the interplay of in-plane magnetic and transverse electric fields in AB-stacked bilayer graphene. In prior work, we demonstrated that this configuration induces an insulator-metal (IM) transition with large impact on the magnetic response, albeit requiring impractically large magnetic fields. Here, we extend the analysis by incorporating previously neglected trigonal warping effects through interlayer skew couplings. In a restricted region of momentum space (on the order of 1/100 of the original Brillouin zone) trigonal warping produces a fine splitting of Dirac cones leading to a compensated semimetallic state in the absence of external fields. Application of a transverse electric field above a small threshold ($V_c\sim 0.6$ meV) reinstates the insulating gap, but this gap can be closed by a relatively small in-plane magnetic field, leading to an IM transition at a much smaller magnetic field ($\approx 10$ T) than previously predicted.