Robust Dirac lines against Ge vacancy and possible spin-orbit Dirac points in nonsymmorphic HfGe0.92Te

TL;DR

This study reports the discovery of multiple Dirac points in HfGe0.92Te, a nonsymmorphic material with vacancies, revealing robust Dirac lines and potential spin-orbit Dirac points, advancing topological material research.

Contribution

The paper introduces HfGe0.92Te as a new material hosting three types of Dirac points, including robust Dirac lines protected by nonsymmorphic symmetry despite vacancies and spin-orbit coupling.

Findings

Observation of Dirac nodal line resilient to SOC and vacancies

Identification of spin-orbit Dirac points from surface states

Confirmation of quasi-2D electronic behavior

Abstract

Looking for new materials with Dirac points has been a fascinating subject of research. Here we report the growth, crystal structure, and band structure of HfGe0.92Te single crystals, featuring three different types of Dirac points. HfGe0.92Te crystalizes in a nonsymmorphic tetragonal space group P4/nmm (No. 129), having square Ge-atom plane with vacancies about 8%. Despite the vacancies on Ge site, the Dirac nodal line composed of conventional Dirac points vulnerable to spin-orbit coupling (SOC) is observed using angle-resolved photoemission spectroscopy, accompanied with the robust Dirac line protected by the nonsymmorphic symmetry against both SOC and vacancies. Specially, spin-orbit Dirac points (SDPs) originated from the surface formed under SOC are hinted to exist according to our experiments and calculations. Quasi-two-dimensional (quasi-2D) characters are observed and further confirmed by angular-resolved magnetoresistance. HfGe0.92Te is a good candidate to explore exotic topological phases or topological properties with three different types of Dirac points and a promising candidate to realize 2D SDPs.