Experimental observation of node-line-like surface states in LaBi

TL;DR

This paper reports the discovery of node-line-like surface states in LaBi, combining experimental ARPES data and first-principles calculations, revealing surface states bridging the band gap and potentially explaining LaBi's unique physical properties.

Contribution

The study provides the first experimental observation of surface states resembling nodal lines in LaBi, expanding understanding of topological surface phenomena in this material.

Findings

Discovery of node-line-like surface states on LaBi (001) surface.

These states bridge the band gap caused by spin-orbit coupling.

Calculated tiny gap in nodal lines exceeds experimental resolution.

Abstract

In a Dirac nodal line semimetal, the bulk conduction and valence bands touch at extended lines in the Brillouin zone. To date, most of the theoretically predicted and experimentally discovered nodal lines derive from the bulk bands of two- and three-dimensional materials. Here, based on combined angle-resolved photoemission spectroscopy measurements and first-principles calculations, we report the discovery of node-line-like surface states on the (001) surface of LaBi. These bands derive from the topological surface states of LaBi and bridge the band gap opened by spin-orbit coupling and band inversion. Our first-principles calculations reveal that these "nodal lines" have a tiny gap, which is beyond typical experimental resolution. These results may provide important information to understand the extraordinary physical properties of LaBi, such as the extremely large magnetoresistance and resistivity plateau.