Perfect valley filter based on topological phase in disordered $\rm{Sb}$ Monolayer Heterostructure

TL;DR

This paper demonstrates that a hydrogenated Sb monolayer heterostructure can serve as a perfect valley filter, maintaining nearly dissipationless, valley-polarized transport even in the presence of moderate disorder and device lengthening.

Contribution

It introduces a novel valley filter based on topological phases in disordered Sb monolayer heterostructures, showing robustness of valley polarization under realistic conditions.

Findings

Nearly perfect valley polarization in disordered conditions.

Disorder destroys QSH edge states but preserves QAH edge states.

Transport current remains stable or improves with device length.

Abstract

The hydrogenated $\rm{Sb}$ monolayer epitaxially grown on a $\rm{LaFeO_3}$ substrate is a novel type of two-dimensional material hosting quantum spin-quantum anomalous Hall (QS-QAH) states. For a device formed by $\rm{Sb}$ monolayer ribbon, the QAH edge states, belong to a single valley, are located at opposite edges of the ribbon. The QSH edge states, on the other hand, belong to the other valley and are distributed in a very narrow region at the same edge. In this paper, we find such material can be used to fabricate perfect valley filter. Adopting scattering matrix method and Green's function method, the valley resolved transport and spatial distribution of local current are calculated, in the present of Anderson disorder, edge defects and edge deformations. The numerical results demonstrate that, in the presence of above three types of disorder with moderate strength, the carriers can flow disspationless with nearly perfect valley polarization. Moreover, when the device becomes longer, the transport current does not decrease while the valley filter works even better. The origin is that the disorder can destroy the QSH edge states, but the valley-polarized QAH edge states can well hold.