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Tunable Josephson diode effect mediated by topological surface states in BiSbTeSe2 Josephson junctions

Si-Li Wu, Zhi-Hui Ren, Peng Zhu, Hao-Chen Zhang, Xue-Tao Di, Chong Wang, Chuan Li, Zhiwei Wang, Cai-Zhen Li, Zhi-Min Liao

DOI 10.1103/3g15-d11l · Physical Review B

T1

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Abstract

Superconducting proximity effects in topological insulators enable novel phenomena such as the Josephson diode effect (JDE), yet disentangling surface and bulk contributions remains challenging. Here we report a tunable JDE mediated by topological surface states in BiSbTeSe2 (BSTS) Josephson junctions. Finite-momentum Cooper pairing of spin-helical surface states gives rise to a pronounced JDE under an in-plane magnetic field, with diode efficiency reaching up to 40%. Temperature-dependent measurements reveal that at higher temperatures, the supercurrent is dominated by surface states, resulting in a rapid increase in diode efficiency upon cooling, while the onset of bulk contributions at lower temperatures leads to efficiency saturation. Gate tuning approaching the Dirac point region enhances surface transport, increasing the diode efficiency from 40% to 50%. These results provide strong evidence for a dominant role of topological surface states in the nonreciprocal superconductivity and establish BSTS junctions as a promising platform for tunable, high-performance superconducting diodes.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
BiSbTeSe2

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5.5Pressure not reportedonset
BiSbTeSe2

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2.4Pressure not reportedonset
Nb

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—Pressure not reportedunknown

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