Experimental study of ac Josephson effect in gate-tunable (Bi1-xSbx)2Te3 thin-film Josephson junctions

Yuusuke Takeshige, Sadashige Matsuo, Russell S. Deacon, Kento Ueda, Yosuke Sato, Yi Fan Zhao, Lingjie Zhou, Cui Zu Chang, Koji Ishibashi, Seigo Tarucha

Research output: Contribution to journalArticle

Abstract

We report on measurements of the ac Josephson effect in three-dimensional topological insulator (TI) Josephson junctions with Fermi energy tuning using a back gate. We successfully tune the Fermi energy into the bulk gap of the TI. We observe that the Josephson energy as a function of the gate voltage has a dip feature, indicating the presence of specular Andreev reflections. We study the ac Josephson effect with detection of both Shapiro steps and Josephson emission. The obtained results show no signature of Majorana modes. With the support of simulations, we conclude that the observation of the fractional ac Josephson effect may be complicated by both a large parallel capacitance and a small ratio of current carried in 4π period modes compared to conventional 2π modes.

Original languageEnglish (US)
Article number115410
JournalPhysical Review B
Volume101
Issue number11
DOIs
StatePublished - Mar 15 2020

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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    Takeshige, Y., Matsuo, S., Deacon, R. S., Ueda, K., Sato, Y., Zhao, Y. F., Zhou, L., Chang, C. Z., Ishibashi, K., & Tarucha, S. (2020). Experimental study of ac Josephson effect in gate-tunable (Bi1-xSbx)2Te3 thin-film Josephson junctions. Physical Review B, 101(11), [115410]. https://doi.org/10.1103/PhysRevB.101.115410