title: Local and nonlocal Fraunhofer-like pattern from an edge-stepped topological surface Josephson current distribution.
abstract: We report a surface-dominant Josephson effect in superconductor-topological insulator-superconductor (S-TI-S) devices, where a Bi1.5Sb0.5Te1.7Se1.3 (BSTS) crystal flake was adopted as an intervening TI between Al superconducting electrodes. We observed a Fraunhofer-type critical current modulation in a perpendicular magnetic field in an Al-TI-Al junction for both local and nonlocal current biasing. Fraunhofer-type modulation of the differential resistance was also observed in a neighboring Au-TI-Au normal junction when it was nonlocally biased by the Al-TI-Al junction. In all cases, the Fraunhofer-like signal was highly robust to the magnetic field up to the critical field of the Al electrodes, corresponding to the edge-stepped nonuniform supercurrent density arising from the top and rough side surfaces of the BSTS flake, which strongly suggests that the Josephson coupling in a TI is established through the surface conducting channels that are topologically protected.
authors.affiliation: Department of Physics, Pohang University of Science and Technology , Pohang 790-784, Republic of Korea.
authors.forename: Jae Hyeong
authors.initials: JH
authors.lastname: Lee
authors.forename: Gil-Ho
authors.initials: GH
authors.lastname: Lee
authors.forename: Joonbum
authors.initials: J
authors.lastname: Park
authors.forename: Janghee
authors.initials: J
authors.lastname: Lee
authors.forename: Seung-Geol
authors.initials: SG
authors.lastname: Nam
authors.forename: Yun-Sok
authors.initials: YS
authors.lastname: Shin
authors.forename: Jun Sung
authors.initials: JS
authors.lastname: Kim
authors.forename: Hu-Jong
authors.initials: HJ
authors.lastname: Lee
keywords: Josephson coupling Fraunhofer interference pattern; Topological insulators; surface pair current