Is SmB₆ a topological insulator?

Abstract

We examined whether samarium hexaboride (SmB₆) is a topological insulator, or not by reviewing and reanalyzing all published experimental results to date. Despite the fact that the SmB₆ has long been known as a Kondo insulator, with strong correlations and band hybridization, it is still of great interest because of low-temperature transport anomalies which have recently been interpreted as evidence that SmB₆ is a topological insulator. SmB₆ behaves electronically at high temperature like an insulator, and at low temperature its resistance mysteriously saturates. We studied de Haas van-Alphen quantum oscillation results to resolve the Fermi surface topology in this material. Although dHvA measurement may be consistent with two-dimensional conducting electronic states, we find an elongated 3D ellipsoidal Fermi surface is also consistent with the experimental results. Furthermore, resistance measurements also can give some evidence of SmB₆ surface conductivity, by studying different geometries to determine whether the conduction is dominated by the surface or the bulk. Also, we simulated the conductivity of a thin sample to assess whether the experimental measurements on their sample are consistent with surface conductivity. After analyzing these experiments and others, our conclusion is that the main experimental results can be described as either bulk or surface conduction, but resistivity measurements strongly suggest surface conduction. Even if further studies prove the surface conductivity, further studies will be required to show that SmB₆ is a topological material.