We report experimental and theoretical evidence that GaGeTe is a basic Z2 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.
@article{arxiv.1812.01668,
title = {Possible Experimental Realization of a Basic Z2 Topological Semimetal},
author = {Erik Haubold and Alexander Fedorov and Igor P. Rusinov and Tatiana V. Menshchikova and Viola Duppel and Daniel Friedrich and Florian Pielnhofer and Richard Weihrich and Arno Pfitzner and Alexander Zeugner and Anna Isaeva and Setti Thirupathaiah and Yevhen Kushnirenko and Emile Rienks and Timur Kim and Evgueni V. Chulkov and Bernd Büchner and Sergey V. Borisenko},
journal= {arXiv preprint arXiv:1812.01668},
year = {2020}
}