Observation of Gapless Dirac Surface States in ZrGeTe

TL;DR

This study reports the discovery of gapless Dirac surface states in ZrGeTe, a nonsymmorphic symmetry protected Dirac semimetal, revealing complex topological phenomena and potential for exploring various quantum phases.

Contribution

It provides the first systematic ARPES investigation and theoretical analysis of ZrGeTe, demonstrating the coexistence of symmorphic and non-symmorphic symmetry protected Dirac states.

Findings

Two Dirac-like gapless surface states observed at the same Brillouin zone point

Surface states are protected by crystalline symmetry as shown by calculations

ZrGeTe exhibits interplay of symmorphic and non-symmorphic symmetries

Abstract

The experimental discovery of the topological Dirac semimetal establishes a platform to search for various exotic quantum phases in real materials. ZrSiS-type materials have recently emerged as topological nodal-line semimetals where gapped Dirac-like surface states are observed. Here, we present a systematic angle-resolved photoemission spectroscopy (ARPES) study of ZrGeTe, a nonsymmorphic symmetry protected Dirac semimetal. We observe two Dirac-like gapless surface states at the same $\bar X$ point of the Brillouin zone. Our theoretical analysis and first-principles calculations reveal that these are protected by crystalline symmetry. Hence, ZrGeTe appears as a rare example of a naturally fine tuned system where the interplay between symmorphic and non-symmorphic symmetry leads to rich phenomenology, and thus opens for opportunities to investigate the physics of Dirac semimetallic and topological insulating phases realized in a single material.