Non-Majorana origin of anomalous current-phase relation and Josephson diode effect in Bi 2 Se 3 /NbSe 2 Josephson junctions
- Andrei Kudriashov
- Xiangyu Zhou
- Razmik A. Hovhannisyan
- Alexander S. Frolov
- Leonid Elesin
- Yi-Bo Wang
- Ekaterina V. Zharkova
- Takashi Taniguchi
- Kenji Watanabe
- Zheng Liu
- Kostya S. Novoselov
- Lada V. Yashina
- Xin Zhou
- Denis A. Bandurin
2025-06-13
Josephson junctions (JJs) are key to superconducting quantum technologies and the search for self-conjugate quasiparticles potentially useful for fault-tolerant quantum computing. In topological insulator (TI)–based JJs, measuring the current-phase relation (CPR) can reveal unconventional effects such as Majorana bound states (MBS) and nonreciprocal transport. However, reconstructing CPR as a function of magnetic field has not been attempted. Here, we present a platform for field-dependent CPR measurements in planar JJs made of NbSe 2 and few-layer Bi 2 Se 3 . When a flux quantum Φ 0 threads the junction, we observe anomalous peak-dip CPR structure and nonreciprocal supercurrent flow. We show that these arise from a nonuniform supercurrent distribution that also leads to a robust and tunable Josephson diode effect. Furthermore, despite numerous previous studies, we find no evidence of MBS. Our results establish magnetic field–dependent CPR as a powerful probe of TI-based superconducting devices and offer design strategies for nonreciprocal superconducting electronics.