Three-dimensional band structure of LaSb and CeSb:Absence of band inversion

TL;DR

This study uses ARPES to investigate the 3D electronic structures of LaSb and CeSb, finding no band inversion and thus confirming their topologically trivial nature, contrary to previous VUV photon results.

Contribution

The paper provides the first accurate 3D bulk band structure of LaSb and CeSb using soft-x-ray ARPES, clarifying their topological triviality.

Findings

No band inversion at the Brillouin-zone corner in LaSb and CeSb.

Soft-x-ray ARPES reveals accurate 3D band structures.

VUV ARPES results are affected by $k_z$ broadening, leading to misinterpretation.

Abstract

We have performed angle-resolved photoemission spectroscopy (ARPES) of LaSb and CeSb, a candidate of topological insulator. Using soft-x-ray photons, we have accurately determined the three-dimensional bulk band structure and revealed that the band inversion at the Brillouin-zone corner - a prerequisite for realizing topological-insulator phase - is absent in both LaSb and CeSb. Moreover, unlike the ARPES data obtained with soft-x-ray photons, those with vacuum ultraviolet (VUV) photons were found to suffer significant $k_z$ broadening. These results suggest that LaSb and CeSb are topologically trivial semimetals, and unusual Dirac-cone-like states observed with VUV photons are not of the topological origin.