Bulk and surface electronic structure of trigonal structured PtBi2 studied by angle-resolved photoemission spectroscopy

TL;DR

This study uses angle-resolved photoemission spectroscopy to analyze the bulk and surface electronic structures of PtBi2, revealing a Dirac-like surface state and significant electron doping, which helps clarify the origin of its large linear magnetoresistance.

Contribution

The paper provides the first detailed experimental distinction between bulk and surface states in PtBi2, identifying a non-topological Dirac surface state and revealing Bi deficiency-induced disorder.

Findings

Discovery of a Dirac-cone-like surface state in PtBi2.

Identification of significant electron doping and Bi deficiency.

Exclusion of quantum-limit effects as the cause of magnetoresistance.

Abstract

PtBi2 with a layered trigonal crystal structure was recently reported to exhibit an unconventional large linear magnetoresistance, while the mechanism involved is still elusive. Using high resolution angle-resolved photoemission spectroscopy, we present a systematic study on its bulk and surface electronic structure. Through careful comparison with first-principle calculations, our experiment distinguishes the low-lying bulk bands from entangled surface states, allowing the estimation of the real stoichiometry of samples. We find significant electron doping in PtBi2, implying a substantial Bi deficiency induced disorder therein. We discover a Dirac-cone-like surface state on the boundary of the Brillouin zone, which is identified as an accidental Dirac band without topological protection. Our findings exclude quantum-limit-induced linear band dispersion as the cause of the unconventional large linear magnetoresistance.