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

NiTe2, 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 NiTe2 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 NiTe2-xSex alloy moves from +0.1 eV (NiTe2) 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 NiTe2 by controlling the SOC strength via chalcogen substitution. This approach can be applicable to different types of topological materials.

Automated summary

In this study, the strength of spin-orbit coupling in NiTe2 is shown to be tunable through Se substitution, resulting in shifts of the bulk Dirac point while maintaining the type-II Dirac band. This approach provides an effective means of controlling the type-II Dirac band in NiTe2 and can be applicable to other topological materials.