Spontaneous superconducting diode effect in non-magnetic Nb/Ru/Sr 2 RuO 4 topological junctions
Non-reciprocal electronic transport in a material occurs if both time reversal and inversion symmetries are broken. The superconducting diode effect (SDE) is an exotic manifestation of this type of behavior where the critical current for positive and negative currents are mismatched, as recently observed in some non-centrosymmetric superconductors with a magnetic field. Here, we demonstrate a SDE in non-magnetic Nb/Ru/Sr2RuO4 Josephson junctions without applying an external magnetic field. The cooling history dependence of the SDE suggests that time-reversal symmetry is intrinsically broken by the superconducting phase of Sr2RuO4. Applied magnetic fields modify the SDE dynamically by randomly changing the sign of the non-reciprocity. We propose a model for such a topological junction with a conventional superconductor surrounded by a chiral superconductor with broken time reversal symmetry.
Acknowledgements: We are grateful to B. Zinkl and G. Mattoni for helpful discussion. We acknowledge the support from International Center for Materials Nanoarchitectonics (MANA) in the National Institute for Materials Science (NIMS), Japan. This work is supported by JSPS KAKENHI (Nos. JP15H05852, JP15K21717, JP22H01168, JP23K17670, JP22H04473 and JP26287078), JSPS-EPSRC Core-to-Core Programme (No. JPJSCCA20170002), and the Swiss National Science Foundation (SNSF) through Division II (No. 184739). M.S.A. and J.W.A.R. acknowledges funding from the EPSRC International Network Grant “Oxide Superspin” (No. EP/P026311/1).