Various Nodal Lines in P63/mmc-type TiTe Topological Metal and its (001) Surface State

Peng Lin,Kai Wang,Yang Li,Fang Fang,Li Zhang

doi:10.3389/fchem.2021.755350

Abstract

Searching for existing topological materials is a hot topic in quantum and computational chemistry. This study uncovers P63/mmc type TiTe compound—an existing material—is a newly discovered topological metal that hosts the various type of nodal line states. Different nodal line states normally exhibit different properties; they may have their individual applications. We report that TiTe hosts I, II, and hybrid type nodal line (NL) states at its ground state without chemical doping and strain engineering effects. Specifically, two type I NLs, two hybrid-type NLs, and one Γ—centered type II NL can be found in the kz = 0 plane. Moreover, the spin-orbit coupling induced gaps for these NLs are very small and within acceptable limits. The surface states of the TiTe (001) plane were determined to provide strong evidence for the appearance of the three types of NLs in TiTe. We also provide a reference for the data of the dynamic and mechanical properties of TiTe. We expect that the proposed NL states in TiTe can be obtained in future experiments.

Highlights

Searching for topological materials in realistic materials in quantum and computational chemistry is a hot research topic
Many nodal line (NL) materials with different NL shapes have been proposed, including nodal ring (Zhang et al, 2018a), nodal chain (Bzdušek et al, 2016), nodal link (Yan et al, 2017), nodal knot (Bi et al, 2017; Ezawa, 2017), and nodal net materials
We show that I, II, and hybrid NLs can be found in the kz 0 plane of TiTe

Summary

INTRODUCTION

Searching for topological materials in realistic materials in quantum and computational chemistry is a hot research topic. In region B, two type II NPs, B1 and B2, belong to a single NL and the Γ-centered 3D band dispersion in region B of the kz 0 plane and the shape of the NL in region B are given in Figures 6A,B, respectively. We use the black circles to indicate the positions of the BCPs. The D-HL surface states, connected to the BCPs and marked by FIGURE 7 | (A,B) K-centered 3D band dispersion in region C of the kz 0 plane from different viewpoints. The SOC-induced gap is very large (50–200 meV) when the material contains heavy elements (Huang et al, 2016; Yamakage et al, 2016; Wang et al, 2020e), which significantly damages the intrinsic electronic properties of the NLs. Figure 8C shows the band structure with. We conclude that the SOC-induced gap for these band-crossings is smaller than 28 meV and within the acceptable limits, reflecting that TiTe is an ideal NL material with robust resistance to the effects of SOC

CONCLUSION

DATA AVAILABILITY STATEMENT