Observation of band crossings protected by nonsymmorphic symmetry in the layered ternary telluride Ta3SiTe6

TL;DR

This study uses angle-resolved photoemission spectroscopy to observe Dirac-like dispersions and nodal lines in Ta3SiTe6, revealing the role of nonsymmorphic symmetry in protecting these electronic features.

Contribution

First experimental observation of nonsymmorphic symmetry-protected nodal lines and hourglass dispersions in Ta3SiTe6 using ARPES.

Findings

Dirac-like dispersions in valence bands

Band degeneracy forming nodal lines at R point

Evidence of hourglass-type dispersions near EF

Abstract

We have performed angle-resolved photoemission spectroscopy of layered ternary telluride Ta3SiTe6 which is predicted to host nodal lines associated with nonsymmorphic crystal symmetry. We found that the energy bands in the valence-band region show Dirac-like dispersions which present a band degeneracy at the R point of the bulk orthorhombic Brillouin zone. This band degeneracy extends one-dimensionally along the whole SR high-symmetry line, forming the nodal lines protected by the glide mirror symmetry of the crystal. We also observed a small band splitting near EF which supports the existence of hourglass-type dispersions predicted by the calculation. The present results provide an excellent opportunity to investigate the interplay between exotic nodal fermions and nonsymmorphic crystal symmetry.