Rashba effect in 2D Janus group-III chalcogenides: Control via atomic-scale structural engineering

Tunable Rashba systems hold significant potential for electron spin manipulation in spintronics and for exploring quantum effects. However, the modulation of the Rashba effect is constrained either by the material's inherent properties or the ineffectiveness of controlling methods. Herein, we perform a comprehensive study of the electronic structure and Rashba effect in two-dimensional (2D) Janus group-III chalcogenide systems based on first-principles calculations and suggest that highly efficient Rashba effect modulation can be directly achieved via targeted geometric structure alteration while preserving its semiconductor properties. Specifically, isolated Rashba splitting is observed around the Fermi level of most 2D Janus group-III chalcogenides with a bandgap range of 1.22 to 2.38 eV and Rashba constants αR ranging from 0.18 to 0.79 eVÅ. Among these Rashba semiconductors, the αR shows a nearly linear increase under biaxial or uniaxial tensile strains and, in most cases, exceeds 1 eVÅ, whereas it exhibits a moderate response to external electric fields. Notably, when 2D materials with larger-lattice constants are used to form heterostructures with Rashba semiconductors, the αR exhibits an increasing trend similar to that observed in strained cases. Efficient Rashba effect control through strains or heterostructures results from local structural changes, enhancing orbital hybridization with one crucial orbital responsible for the splitting, and thereby leading to an increased Rashba constant. Our work showcases a Rashba effect modulation strategy achieved via targeted geometric structure engineering, which can be generalized to other Rashba systems given specific conditions, thereby offering crucial insights for advancing the development of controllable spintronic devices.