Universality test of the quantum Hall effect on topological insulator

Progress toward a universality test of the quantum Hall effect on topological insulator is presented. In order to measure the quantized Hall resistance on topological insulator precisely, it is critically important to reduce bulk carrier conduction. Therefore, S 11 -doped Bi 1.1 Sb 0.9 Te 2 S, a newly found topological insulator, was used for the measurement material, and its single crystals were exfoliated into thin flakes. The S 11 -doped Bi 1.1 Sb 0.9 Te 2 S flakes are processed into measurement devices with multiple electrodes for four-probe measurement. Future prospects for the precise measurements using a cryogenic current comparator are also noted.