In-plane electric polarization of bilayer graphene nanoribbons by interlayer bias voltage

TL;DR

This paper demonstrates that applying an interlayer bias voltage to AB-stacked bilayer graphene nanoribbons induces an electric polarization along the ribbon, with behavior depending on ribbon width and bias strength, explained through theoretical models.

Contribution

It reveals the in-plane electric polarization induced by interlayer bias in bilayer graphene nanoribbons and explains the dependence on ribbon width and bias strength using effective and topological models.

Findings

Polarization depends on ribbon width modulo three at weak bias.

Strong bias leads to polarization of one-third or zero, consistent with topological predictions.

Both tight-binding and ab initio calculations agree on polarization behavior.

Abstract

We theoretically show that an interlayer bias voltage in the AB-stacked bilayer graphene nanoribbons with armchair edges induces an electric polarization along the ribbon. Both tight-binding and ab initio calculations consistently indicate that when the bias voltage is weak, the polarization shows opposite signs depending on the ribbon width modulo three. This nontrivial dependence is explained using a two-band effective model. A strong limit of the bias voltage in the tight-binding model shows either one-third or zero polarization, which agrees with topological argument.