Controlling Spin-Orbit Coupling to Tailor Type-II Dirac Bands.

Lam, Nguyen Huu; Nguyen, Phuong Lien; Choi, Byoung Ki; Ly, Trinh Thi; Duvjir, Ganbat; Rhee, Tae Gyu; Jo, Yong Jin; Kim, Tae Heon et al. · ACS Nano · 2022

basic_science · Level V

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Abstract

NiTe<sub>2</sub>, a type-II Dirac semimetal with a strongly tilted Dirac band, has been explored extensively to understand its intriguing topological properties. Here, using density functional theory calculations, we report that the strength of the spin-orbit coupling (SOC) in NiTe<sub>2</sub> can be tuned by Se substitution. This results in negative shifts of the bulk Dirac point (BDP) while preserving the type-II Dirac band. Indeed, combined studies using scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy confirm that the BDP in the NiTe<sub>2-<i>x</i></sub>Se<sub><i>x</i></sub> alloy moves from +0.1 eV (NiTe<sub>2</sub>) to -0.3 eV (NiTeSe) depending on the Se concentrations, indicating the effective tunability of type-II Dirac Fermions. Our results demonstrate an approach to tailor the type-II Dirac band in NiTe<sub>2</sub> by controlling the SOC strength via chalcogen substitution. This approach can be applicable to different types of topological materials.