A SURVEY OF SPIN-ORBIT COUPLING EFFECT IN ASYMMETRICAL TRANSITION METAL CHALCOGENIDES

Abstract

In this thesis, we present a 1st principle study on a series of Janus monolayers of Transition Metal Dichalcogenides (TMD) with the chemical formula MSeTe (M = Hf, Ta, W, Re, Os, Ir, Pt and Au) which are modified from MSe2 by replacing one layer of Se atoms with Te atoms. We focus on Spin-Orbit Coupling in these materials in believe that the absence of spatial inversion symmetry would bring about significant Rashba effect. Among the materials studied, we have identified Rashba splitting on 2H WSeTe (0.54 eV Å), 1T OsSeTe (1.5 eV Å) and 1T IrSeTe (2.7 eV Å) with the confirmation from both electron bands and spin textures. 2H WSeTe bears the most potential in applications due to its semiconducting nature. Dresselhaus effect is abundant in these materials, with the lattice growth direction parallel to the plane. In addition, band splittings are also identified on some materials around high symmetry points. Last but not least, the common believe of a positive correlation between atomic number and Rashba effect is not agreed by the results in this study. Thus we suggest that researchers take bond lengths into account when seeking Rashba effect in 2D materials.