Scale-invariant large nonlocality in polycrystalline graphene

TL;DR

This paper demonstrates scale-invariant nonlocal transport in large-scale polycrystalline graphene, driven by field-induced spin-filtered edge states, highlighting the influence of structural morphology on topological Hall effects.

Contribution

It reveals that nonlocal transport in large-scale graphene is governed by spin-filtered edge states sensitive to grain boundaries, expanding understanding of topological effects in polycrystalline materials.

Findings

Nonlocal resistance persists up to millimeter scale.

Field-induced spin-filtered edge states explain the nonlocal transport.

Polycrystalline morphology influences topological Hall effects.

Abstract

The observation of large nonlocal resistances near the Dirac point in graphene has been related to a variety of intrinsic Hall effects, where the spin or valley degrees of freedom are controlled by symmetry breaking mechanisms. Engineering strong spin or valley Hall signals on scalable graphene devices could stimulate further practical developments of spin- and valleytronics. Here we report on scale-invariant nonlocal transport in large-scale chemical vapour deposition graphene under an applied external magnetic field. Contrary to previously reported Zeeman spin Hall effect, our results are explained by field-induced spin-filtered edge states whose sensitivity to grain boundaries manifests in the nonlocal resistance. This phenomenon, related to the emergence of the quantum Hall regime, persists up to the millimeter scale, showing that polycrystalline morphology can be imprinted in nonlocal transport. This suggests that topological Hall effects in large-scale graphene materials are highly sensitive to the underlying structural morphology, limiting practical realizations.