# Possible Experimental Realization of a Basic Z2 Topological Semimetal

## TL;DR

This paper presents evidence that GaGeTe is a Z2 topological semimetal with unique electronic properties, including multiple charge carriers and a peculiar band structure, which could impact future topological material applications.

## Contribution

It provides the first experimental and theoretical demonstration of GaGeTe as a Z2 topological semimetal with distinctive electronic features.

## Key findings

- GaGeTe hosts bulk electrons, holes, and surface electrons.
- Band structure calculations reveal a small indirect gap with band inversion.
- The material exhibits a unique coexistence of electron and hole carriers at the Fermi level.

## Abstract

We report experimental and theoretical evidence that GaGeTe is a basic $Z_2$ topological semimetal with three types of charge carriers: bulk-originated electrons and holes as well as surface state electrons. This electronic situation is qualitatively similar to the primer 3D topological insulator Bi2Se3, but important differences account for an unprecedented transport scenario in GaGeTe. High-resolution angle-resolved photoemission spectroscopy combined with advanced band structure calculations show a small indirect energy gap caused by a peculiar band inversion in the \textit{T}-point of the Brillouin zone in GaGeTe. An energy overlap of the valence and conduction bands brings both electron- and hole-like carriers to the Fermi level, while the momentum gap between the corresponding dispersions remains finite. We argue that peculiarities of the electronic spectrum of GaGeTe have a fundamental importance for the physics of topological matter and may boost the material's application potential.