Discovery of a weak topological insulating state and van Hove singularity in triclinic RhBi2

Kyungchan Lee,Benjamin Schrunk,Robert-Jan Slager,Gunnar F Lange,Peter P Orth,Brinda Kuthanazhi,Adam Kaminski,Na Hyun Jo,Thaís V Trevisan,Paul C Canfield,Lin-Lin Wang

doi:10.1038/s41467-021-22136-w

Kyungchan Lee, Benjamin Schrunk + Show 9 more

Open Access

https://doi.org/10.1038/s41467-021-22136-w

Copy DOI

Abstract

Time reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development. Apart from TRS protected strong TIs, it was realized early on that more confounding weak topological insulators (WTI) exist. WTIs depend on translational symmetry and exhibit topological surface states only in certain directions making it significantly more difficult to match the experimental success of strong TIs. We here report on the discovery of a WTI state in RhBi2 that belongs to the optimal space group Pbar{1}, which is the only space group where symmetry indicated eigenvalues enumerate all possible invariants due to absence of additional constraining crystalline symmetries. Our ARPES, DFT calculations, and effective model reveal topological surface states with saddle points that are located in the vicinity of a Dirac point resulting in a van Hove singularity (VHS) along the (100) direction close to the Fermi energy (EF). Due to the combination of exotic features, this material offers great potential as a material platform for novel quantum effects.

Highlights

Time reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development
Due to the absence of additional symmetries none of these high symmetry momenta are related and a weak topological insulators (WTI) can exist in every stacking direction[8]. This carefully selected, simple structure makes this the only space group in which the symmetry eigenvalues at time-reversal invariant momentum (TRIM) points convey all topological invariants one-to-one[9,10,11,12]. We find that this freedom of choosing the stacking direction culminates in an index, (0;001), that is perpendicular to the layering of the material, creating the possibility of a topological surface state (TSS) preserving cleavage plane
Due to the symmetry group hosting only an inversion center, the layered triclinic RhBi2 is an interesting case in terms of both band structure and topology

Summary

Introduction

Time reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development. In order to verify the nontrivial topological nature of triclinic RhBi2, we performed ARPES measurements and DFT calculations to identify relevant features in the electronic structure.

Results

Conclusion