Gapped Dirac materials and quantum valley currents in dual-gated hBN/bilayer-graphene heterostructures

TL;DR

This paper demonstrates tunable valley currents in gapped bilayer graphene heterostructures, showing nonlocal resistance consistent with the valley Hall effect and quantum valley currents at low temperatures.

Contribution

It reports the observation of tunable valley currents and nonlocal resistance in hBN/bilayer-graphene heterostructures, advancing understanding of quantum valley phenomena.

Findings

Significant nonlocal resistance observed.

Nonlocal resistance approaches saturation near the quantum limit.

Valley currents are tunable via electric displacement field.

Abstract

In gapped Dirac materials, the topological current associated with each valley can flow in opposite directions creating long-range charge-neutral valley currents. We report valley currents in hBN/bilayer-graphene heterostructures with an energy gap, which is tunable by a perpendicular electric (displacement) field in a dual-gated structure. We observed significant nonlocal resistance, consistent with the scaling theory of the valley Hall effect. In the low-temperature limit, the nonlocal resistance approaches a saturated value near the "quantum limit," indicating the emergence of quantum valley currents.