Electronic structure associated with nonsymmorphic nodal lines in rare-earth tetraborides

Authors:
Open Access
Publisher website
Google Scholar
Abstract
We report a combined microfocused angle-resolved photoemission spectroscopy and first-principles study of the rare-earth tetraborides R B 4 ( R = Tb , Gd ) , which host a Shastry-Sutherland lattice. We identify extended bulk nodal lines at the tetragonal Brillouin-zone boundaries, whose fourfold degeneracies are enforced by the nonsymmorphic glide-mirror symmetries even in the presence of spin-orbit coupling (SOC), unlike conventional nodal lines that SOC typically gaps. Systematically evolving Dirac-like dispersions resolved by momentum-distribution-curve analysis support this symmetry-enforced nodal line. We further identify a related nodal-line feature that disperses toward the Fermi level ( E F ) ; although the calculated SOC-induced gap for this feature (0.2–4.6 meV) lies below the experimental resolution, its proximity to E F offers a band-structure basis consistent with the emergence of large magnetoresistance. First-principles Wilson-loop calculations establish a nontrivial π Berry phase for the bulk nodal line, and we observe a photon-energy-independent surface-derived feature whose dispersion is consistent with the calculated surface state. Our results identify R B 4 as a platform for nonsymmorphic-symmetry-enforced nodal-line physics with potential relevance to large magnetoresistance and topological surface states.
Funding Information
  • Japan Science and Technology Corporation (JPMJCR18T1)
  • Japan Science and Technology Corporation (JPMJAP2512)
  • Japan Society for the Promotion of Science (JP24K00564)
  • Japan Society for the Promotion of Science (JP25H00598)
  • High Energy Accelerator Research Organization (2024G141)
  • High Energy Accelerator Research Organization (2024G136)
  • High Energy Accelerator Research Organization (2026G159)
  • High Energy Accelerator Research Organization (2021S2-001)
  • High Energy Accelerator Research Organization (2024S2-001)
  • Tohoku University

This publication has 82 references indexed in Scilit: