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

Nguyen Huu Lam; Phuong Lien Nguyen; Byoung Ki Choi; Trinh Thi Ly; Ganbat Duvjir; Tae Gyu Rhee; Yong Jin Jo; Tae Heon Kim; Chris Jozwiak; Aaron Bostwick; Eli Rotenberg; Younghun Hwang; Young Jun Chang; Jaekwang Lee; Jungdae Kim

doi:10.1021/acsnano.2c04301

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

ACS Nano. 2022 Jul 26;16(7):11227-11233. doi: 10.1021/acsnano.2c04301. Epub 2022 Jul 15.

Authors

Nguyen Huu Lam¹, Phuong Lien Nguyen², Byoung Ki Choi^{3

4}, Trinh Thi Ly¹, Ganbat Duvjir¹, Tae Gyu Rhee^{4

5}, Yong Jin Jo¹, Tae Heon Kim¹, Chris Jozwiak³, Aaron Bostwick³, Eli Rotenberg³, Younghun Hwang⁶, Young Jun Chang^{4

5}, Jaekwang Lee², Jungdae Kim¹

Affiliations

¹ Department of Physics, University of Ulsan, Ulsan 44610, Republic of Korea.
² Department of Physics, Pusan National University, Busan 46241, Republic of Korea.
³ Advanced Light Source (ALS), E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁴ Department of Physics, University of Seoul, Seoul 02504, Republic of Korea.
⁵ Department of Smart Cities, University of Seoul, Seoul 02504, Republic of Korea.
⁶ Electricity and Electronics and Semiconductor Applications, Ulsan College, Ulsan 44610, Republic of Korea.

PMID: 35838605
DOI: 10.1021/acsnano.2c04301

Abstract

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 NiTe_2-xSe_x 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.

Keywords: NiTe2; NiTe2−xSex; angle-resolved photoelectron spectroscopy; density functional theory; scanning tunneling microscopy/scanning tunneling spectroscopy; spin−orbit coupling; type-II Dirac band.