Charge fractionalization in biased bilayer graphene

TL;DR

This paper investigates charge fractionalization in biased bilayer graphene, revealing how bias induces zero modes and enables fractional charge states, with potential for experimental detection of edge states.

Contribution

It demonstrates that bias in bilayer graphene creates conditions for charge fractionalization by inducing zero modes and breaking valley degeneracy.

Findings

Bias induces zero modes enabling fractional charges.

Localized zero modes can be constructed at zigzag edges.

Layer asymmetry allows detection of distinct charge-1/2 edge states.

Abstract

We study charge fractionalization in bilayer graphene which is intimately related to its zero modes. In the unbiased case, the valley zero modes occur in pairs rendering it unsuitable for charge fractionalization. A bias plays the role of a bosonic field with nontrivial topology allowing for the exploration of Dirac-like dynamics at higher particle momenta. It also induces an odd number of zero modes, which, together with the conjugation symmetry between positive and negative energy states, are the requisite conditions for charge fractionalization. A self-conjugate, localized zero mode is constructed for a semi-infinite graphene sheet with zigzag edge; scenarios can occur readily where one sublattice component (pseudospin) dominates. While the other valley also has a similar zero mode, a layer asymmetry can be invoked to lift this degeneracy allowing for detection of distinguishable charge-1/2 edge states per valley.