Intrinsic valley Hall transport in atomically thin MoS2

TL;DR

This paper reports the first observation of intrinsic valley Hall transport in atomically thin MoS2, demonstrating topological valley effects without extrinsic symmetry breaking, even at room temperature, advancing valleytronics.

Contribution

It provides the first experimental evidence of intrinsic valley Hall effects in monolayer and trilayer MoS2 without external symmetry breaking.

Findings

Intrinsic valley Hall effect observed in monolayer and trilayer MoS2

Valley Hall signal absent in centrosymmetric bilayer MoS2

Room temperature valley Hall transport with micron-scale valley diffusion length

Abstract

Electrons hopping in two-dimensional honeycomb lattices possess a valley degree of freedom in addition to charge and spin. In the absence of inversion symmetry, these systems were predicted to exhibit opposite Hall effects for electrons from different valleys. Such valley Hall effects have been achieved only by extrinsic means, such as substrate coupling, dual gating, and light illuminating. Here, we report the first observation of intrinsic valley Hall transport without any extrinsic symmetry breaking in the non-centrosymmetric monolayer and trilayer MoS2, evidenced by considerable nonlocal resistance that scales cubically with local resistance. Such a hallmark survives even at room temperature with a valley diffusion length at micron scale. By contrast, no valley Hall signal is observed in the centrosymmetric bilayer MoS2. Our work elucidates the topological quantum origin of valley Hall effects and marks a significant step towards the purely electrical control of valley degree of freedom in topological valleytronics.