Quantum transport of two-dimensional Dirac fermions in SrMnBi2

TL;DR

This study demonstrates two-dimensional Dirac fermion behavior in SrMnBi2, revealing unusual linear magnetoresistance and quantum oscillations indicative of 2D electronic states, with potential for low-dimensional transport applications.

Contribution

First observation of 2D Dirac fermion quantum transport in SrMnBi2, highlighting its unique magnetoresistance and electronic properties related to Bi square nets.

Findings

Linear nonsaturated magnetoresistance due to Dirac fermions

Crossover from quadratic to linear magnetoresistance at a critical field

Dominant two-dimensional Fermi surface characteristics

Abstract

We report two-dimensional quantum transport in SrMnBi$_2$ single crystals. The linear energy dispersion leads to the unusual nonsaturated linear magnetoresistance since all Dirac fermions occupy the lowest Landau level in the quantum limit. The transverse magnetoresistance exhibits a crossover at a critical field $B^*$ from semiclassical weak-field $B^2$ dependence to the high-field linear-field dependence. With increase in the temperature, the critical field $B^*$ increases and the temperature dependence of $B^*$ satisfies quadratic behavior which is attributed to the Landau level splitting of the linear energy dispersion. The effective magnetoresistant mobility $\mu_{MR}\sim 3400$ cm$^2$/Vs is derived. Angular dependent magnetoresistance and quantum oscillations suggest dominant two-dimensional (2D) Fermi surfaces. Our results illustrate the dominant 2D Dirac fermion states in SrMnBi$_2$ and imply that bulk crystals with Bi square nets can be used to study low dimensional electronic transport commonly found in 2D materials like graphene.