Surface electronic structure of topological Kondo insulator candidate SmB6: a high-resolution ARPES study*

The Kondo insulator SmB6 has been known to exhibit low temperature transport anomaly and has recently attracted attention as a new topological insulator candidate. By combining low temperature and high resolution of the laser-based ARPES, for the first time, we probe the surface electronic structure of the anomalous conductivity regime. We observe that the bulk bands exhibit a Kondo gap of 14 meV and identify in-gap low-lying states within 4 meV of the Fermi level on the surface of this material. The low-lying states are found to form electron-like Fermi surface pockets that enclose the X and the $\Gamma$ points of the surface BZ. These states disappear as temperature is raised in correspondence with the complete disappearance of the 2D conductivity channels. While the topological nature of the in-gap metallic states cannot be ascertained, our measurements are consistent with the predicted first-principle topological Kondo insulator phase in this material.