Signature of topological states in antiferromagnetic Sm-substituted Bi2Te3

Abstract

An antiferromagnetic topological insulator has been predicted to be preserved by breaking both time-reversal symmetry and primitive lattice translational symmetry. However, the topological surface state has often been observed to disappear in an antiferromagnetic phase because the doped magnetic impurity acts as an extrinsic defect. In this study, we report the experimental signature of topological surface states coexisting with antiferromagnetic order in Sm-doped Bi2Te3. We fabricate single crystals of SmxBi2-xTe3 with x = 0.004, 0.010, and 0.025, where the Curie-Weiss law is satisfied at low temperatures but is violated at high temperatures due to the influence of the high energy states of J multiplets of Sm. For x = 0.025, e xotic physical properties are observed, such as the antiferromagnetic phase with the Néel temperature TN = 3.3 K, multi-band Hall effect with two conduction channel, and anisotropic Shubnikov-de Haas oscillations. In the antiferromagnetic phase, we detect the signature of nontrivial topological surface states with surface electron density ns = 7.9 × 1011 cm-2 and its high mobility μs = 2,200 cm2/Vs, compared to nb = 2.0 × 1019 cm-3 and μb = 2.3 cm2/Vs for bulk electrons. These observations suggest that SmxBi2-xTe3 is a candidate creating the new stage for the potential application of topological antiferromagnetic spintronics.