Valley-contrasting Spin Textures in Janus Metal Phosphochalcogenides

TL;DR

This paper investigates Janus MP$_2$S$_3$Se$_3$ monolayers, revealing diverse, tunable spin textures at different valleys and their coupling to valley-dependent electronic and optical properties, with implications for spintronics and valleytronics.

Contribution

It demonstrates the coexistence and tunability of multiple spin textures and valley-dependent properties in Janus MP$_2$S$_3$Se$_3$ monolayers using first-principles calculations.

Findings

Distinct spin textures at different valleys, including Ising, Weyl, and Rashba types.

Valley-dependent Berry curvature and anomalous Hall effects.

Strain-tunable band gaps and energy differences between valleys.

Abstract

Momentum-resolved spin textures and potential valley-contrasting physical properties in the momentum space are two intriguing characteristics of noncentrosymmetric materials, and they have broad applications in spintronics and valleytronics. The realization of diverse spin textures within a single material, along with their further coupling to the valley degree of freedom, is highly desirable. Via first-principles calculations, we investigate electronic properties of Janus MP$_2$S$_3$Se$_3$ monolayers, which exhibits distinct spin textures at different valleys. While Ising-type spin textures are located at $K_\pm$ valleys, the symmetry breaking from the Janus structure brings about a coexistence of Weyl-type and Rashba-type spin textures at $\Gamma$ valley. In addition to valley-contrasting spin textures, valley dependence also occurs in Berry-curvature-driven anomalous Hall currents and optical selectivity. Besides, energy differences between $\Gamma$ and $K_\pm$, as well as band gaps, are highly tunable by applied strain. These findings present an intriguing coupling between diverse spin textures and multiple valleys, and pave the way for designing advanced electronic devices that leverage spin and valley degrees of freedom.