Single-surface conduction in a highly bulk-resistive topological insulator Sn0.02Bi1.08Sb0.9Te2S using the Corbino geometry

To realize the single-surface conduction in a topological insulator, a microscale Corbino device was fabricated from a single crystal of a highly bulk-resistive topological insulator Sn0.02Bi1.08Sb0.9Te2S (Sn-BSTS). The four-terminal resistance was measured in 2 K–300 K, and it was found that the temperature dependence of the resistance of the Corbino device was clearly distinct from that of Sn-BSTS bulk samples. We showed that the unconventional behavior of the Corbino device was quantitatively understood by considering the top surface, bottom surface, and bulk as independent conduction paths in parallel. Furthermore, the current flow distribution was studied by introducing the resistance network model, which revealed that the top-surface dominant conduction was realized in a low temperature. This study demonstrates the usefulness of the Corbino geometry for transport measurement in topological insulators.