Large valleys splitting under biaxial strain in Janus SHfAX2(A=Si, Ge; X=N, P, As)

Abstract

The exploration of valley physics in 2D materials exhibiting strong spin-orbit coupling (SOC) holds fundamental significance. In this work, we demonstrate that the 2D Janus SHfAX2 (A=Si, Ge; X=N, P, As) family emerges as a promising 2D valley material from first-principles calculations. We find that there is a large valley splitting at the K and K′ points in the 2D SHfAX2. This splitting predominantly originates from its strong SOC effect and the built-in electric field in the Janus structure. The spin states of valley splitting remain stable under the biaxial strain ranging from −4% to 4%. In this study, the conduction band exhibits a peak in the Berry curvature related to valley splitting at the K/K' points. Moreover, the carriers in the K/K' valleys accumulate at the opposite edges of the nanoribbons, generating the valley Hall effect. The 2D SHfAX2 has high mechanical and dynamic stability, thus providing an emerging family of 2D materials targeting real-world valley-based devices