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

doi:10.1103/PhysRevB.101.115410

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

Physics

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9 Scopus citations

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 language	English (US)
Article number	115410
Journal	Physical Review B
Volume	101
Issue number	11
DOIs	https://doi.org/10.1103/PhysRevB.101.115410
State	Published - Mar 15 2020

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

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10.1103/PhysRevB.101.115410

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

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.",

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

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doi = "10.1103/PhysRevB.101.115410",

language = "English (US)",

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T1 - Experimental study of ac Josephson effect in gate-tunable (Bi1-xSbx)2Te3 thin-film Josephson junctions

AU - Takeshige, Yuusuke

AU - Matsuo, Sadashige

AU - Deacon, Russell S.

AU - Ueda, Kento

AU - Sato, Yosuke

AU - Zhao, Yi Fan

AU - Zhou, Lingjie

AU - Chang, Cui Zu

AU - Ishibashi, Koji

AU - Tarucha, Seigo

PY - 2020/3/15

Y1 - 2020/3/15

N2 - 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.

AB - 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.

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

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