Edge dependece of nonlocal transport in gapped bilayer graphene

TL;DR

This study investigates how edge-etching affects electron transport in gapped bilayer graphene, revealing that edge conduction pathways, not topological properties, dominate nonlocal resistance after etching.

Contribution

It demonstrates that edge-etching creates conducting pathways that significantly alter nonlocal resistance, challenging previous claims of topological origins in gapped BLG transport.

Findings

Edge-etching induces edge conduction pathways.

Nonlocal resistance deviates from ohmic behavior after etching.

Edge conduction, not topology, explains resistance changes.

Abstract

The topological properties of gapped graphene have been explored for valleytronics applications. Prior transport experiments indicated their topological nature through large nonlocal resistance in Hall-bar devices, but the origin of this resistance was unclear. This study focused on dual-gate bilayer graphene (BLG) devices with naturally cleaved edges, examining how edge-etching with an oxygen plasma process affects electron transport. Before etching, local resistance at the charge neutral point increased exponentially with the displacement field and nonlocal resistance was well explained by ohmic contribution, which is typical of gapped BLG. After-etching, however, local resistance saturated with increasing displacement field, and nonlocal resistance deviated by three orders of magnitude from ohmic contribution. We suggest that these significant changes in local and nonlocal resistance arise from the formation of edge conducting pathways after the edge-etching, rather than from a topological property of gapped BLG that has been claimed in previous literatures.