Two-Dimensional Mineral [Pb2BiS3][AuTe2]: High-Mobility Charge Carriers in Single-Atom-Thick Layers

Two-dimensional (2D) electronic systems are of wide interest due to their richness in chemical and physical phenomena and potential for technological applications. Here we report that [Pb2BiS3]­[AuTe2], known as the naturally occurring mineral buckhornite, hosts 2D carriers in single-atom-thick layers. The structure is composed of stacking layers of weakly coupled [Pb2BiS3] and [AuTe2] sheets. The insulating [Pb2BiS3] sheet inhibits interlayer charge hopping and confines the carriers in the basal plane of the single-atom-thick [AuTe2] layer. Magneto-transport measurements on synthesized samples and theoretical calculations show that [Pb2BiS3]­[AuTe2] is a multiband semimetal with a compensated density of electrons and holes, which exhibits a high hole carrier mobility of ∼1360 cm2/(V s). This material possesses an extremely large anisotropy, Γ = ρc/ρab ≈ 104, comparable to those of the benchmark 2D materials graphite and Bi2Sr2CaCu2O6+δ. The electronic structure features linear band dispersion at the Fermi level and ultrahigh Fermi velocities of 106 m/s, which are virtually identical to those of graphene. The weak interlayer coupling gives rise to the highly cleavable property of the single crystal specimens. Our results provide a novel candidate for a monolayer platform to investigate emerging electronic properties.