Title : Fractional Josephson effects in Dirac materials

일시 : 2023년 12월 05일(화), 17시

Speaker : 도용주 (GIST)

Abstract : Topological insulators (TIs) are bulk insulators including metallic surface states, which are topologically protected by time-reversal symmetry. TI nanoribbon combined with conventional s-wave superconductor is expected to host the Majorana zero modes, which is essential for the topological quantum computation. Here, we report our experimental observations of fractional Josephson effects in Sb-doped Bi2Se3 TI nanoribbons in contact with PbIn superconducting electrodes. The existence of topological surface states in TI nanoribbons was confirmed by the Aharonov-Bohm (AB) oscillations of magnetoconductance with the axial magnetic field along the nanoribbon axis. Below the superconducting transition temperature, we observed the AB-type oscillations of the supercurrent with the axial magnetic field. Under the application of microwave, Shapiro steps were observed except the first step. The first-step missing behavior is attributed to the 4-periodic topological supercurrent. Our observations indicate that topological Dirac materials would be a promising building block for the development of topological superconducting quantum devices.