Topological surface conduction in Kondo insulator YbB$_{12}$

TL;DR

This study provides transport evidence for topologically protected surface conduction in the Kondo insulator YbB$_{12}$, supporting its classification as a topological Kondo insulator with surface states and quantum oscillations in the insulating bulk.

Contribution

It offers experimental evidence of surface conduction and topological surface states in YbB$_{12}$, a prototype Kondo insulator, using transport measurements and high magnetic field data.

Findings

Surface conduction decreases with sample thickness.

Weak-antilocalization effect observed at low magnetic fields.

Quantum oscillations occur in the insulating bulk of YbB$_{12}$.

Abstract

Kondo insulators have recently aroused great interest because they are promising materials that host a topological insulator state caused by the strong electron interactions. Moreover, recent observations of the quantum oscillations in the insulating state of Kondo insulators have come as a great surprise. Here, to investigate the surface electronic state of a prototype Kondo insulator YbB$_{12}$, we measured transport properties of single crystals and microstructures. In all samples, the temperature dependence of the electrical resistivity is insulating at high temperatures and the resistivity exhibits a plateau at low temperatures. The magnitude of the plateau value decreases with reducing sample thickness, which is quantitatively consistent with the surface electronic conduction in the bulk insulating YbB$_{12}$. Moreover, the magnetoresistance of the microstructures exhibits a weak-antilocalization effect at low field. These results are consistent with the presence of topologically protected surface state, suggesting that YbB$_{12}$ is a candidate material of the topological Kondo insulator. The high field resistivity measurements up to $\mu_0H$ = 50 T of the microstructures provide supporting evidence that the quantum oscillations of the resistivity in YbB$_{12}$ occurs in the insulating bulk.