Quantum transport of two-dimensional Dirac fermions in SrMnBi_2

摘要

We report two-dimensional quantum transport in SrMnBi_2 single crystals. The linear energy dispersion leads to 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 an increase in temperature, the critical field B* increases and the temperature dependence of B* satisfies the quadratic behavior which is attributed to the Landau-level splitting of the linear energy dispersion. The effective magnetoresistant mobility μ_(MR) ～ 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 such as graphene.