Non-symmorphic band degeneracy at the Fermi level in ZrSiTe

TL;DR

This paper reports the discovery of non-symmorphic symmetry-induced Dirac line nodes at the Fermi level in ZrSiTe, enabling direct transport studies of exotic Dirac fermions originating from non-symmorphic symmetry.

Contribution

The study provides experimental evidence and theoretical analysis of non-symmorphic symmetry-induced Dirac crossings at the Fermi level in ZrSiTe, a first for such materials.

Findings

ZrSiTe hosts fourfold degenerate Dirac crossings at the X point.

A Dirac line node along XR is located near the Fermi level.

ZrSiTe enables transport measurements of non-symmorphic Dirac fermions.

Abstract

Non-symmorphic materials have recently been predicted to exhibit many different exotic features in their electronic structures. These originate from forced band degeneracies caused by the non-symmorphic symmetry, which not only creates the possibility to realize Dirac semimetals, but also recently resulted in the prediction of novel quasiparticles beyond the usual Dirac, Weyl or Majorana fermions, which can only exist in the solid state. Experimental realization of non-symmorphic materials that have the Fermi level located at the degenerate point is difficult, however, due to the requirement of an odd band filling. In order to investigate the effect of forced band degeneracies on the transport behavior, a material that has such a degeneracy at or close to the Fermi level is desired. Here, we show with angular resolved photoemission experiments supported by density functional calculations, that ZrSiTe hosts several fourfold degenerate Dirac crossings at the X point, resulting from non-symmorphic symmetry. These crossings form a Dirac line node along XR, which is located almost directly at the Fermi level and shows almost no dispersion in energy. ZrSiTe is thus the first real material that allows for transport measurements investigating Dirac fermions that originate from non-symmorphic symmetry.