Multiple Dirac cones at the surface of the topological metal LaBi

TL;DR

This study uses ARPES and calculations to discover multiple Dirac cones on LaBi's surface, confirming its topological semi-metal nature and explaining its magneto-transport phenomena.

Contribution

It provides the first experimental evidence of topological surface states in LaBi through the observation of multiple Dirac cones.

Findings

Three Dirac cones observed on LaBi surface

Odd number of Dirac cones confirms topological semi-metallic phase

Surface states linked to bulk band inversions

Abstract

The rare-earth monopnictide LaBi exhibits exotic magneto-transport properties including an extremely large and anisotropic magnetoresistance. Experimental evidence for topological surface states is still missing although band inversions have been postulated to induce a topological phase in LaBi. By employing angle-resolved photoemission spectroscopy (ARPES) in conjunction with $ab~initio$ calculations, we have revealed the existence of surface states of LaBi through the observation of three Dirac cones: two coexist at the corners and one appears at the center of the Brillouin zone. The odd number of surface Dirac cones is a direct consequence of the odd number of band inversions in the bulk band structure, thereby proving that LaBi is a topological, compensated semi-metal, which is equivalent to a time-reversal invariant topological insulator. Our findings provide insight into the topological surface states of LaBi's semi-metallicity and related magneto-transport properties.