Polarization and valley switching in monolayer group-IV monochalcogenides

TL;DR

This paper demonstrates that monolayer SnS and GeSe exhibit multistability and valley polarization controllable by stress and electric fields, with potential for ferroelectric and information storage applications.

Contribution

It reveals the multistability and valley switching in monolayer SnS and GeSe using first principles calculations, highlighting their ferroelectric potential.

Findings

Puckering direction can be switched by tensile stress or electric field.

Valleys in momentum space can be selectively excited with polarized light.

Monolayers show potential for ferroelectricity and multistability.

Abstract

Group-IV monochalcogenides are a family of two-dimensional puckered materials with an orthorhombic structure that is comprised of polar layers. In this article, we use first principles calculations to show the multistability of monolayer SnS and GeSe, two prototype materials where the direction of the puckering can be switched by application of tensile stress or electric field. Furthermore, the two inequivalent valleys in momentum space, which are dictated by the puckering orientation, can be excited selectively using linearly polarized light, and this provides an additional tool to identify the polarization direction. Our findings suggest that SnS and GeSe monolayers may have observable ferroelectricity and multistability, with potential applications in information storage.