Probing the Josephson effect in twisted nodal superconductors
ORAL
Abstract
Motivated by the recent proposals for unconventional emergent physics in twisted bilayers of nodal superconductors, we study the Josephson effect at the twisted interface between d-wave superconductors. We demonstrate that the critical current can exhibit a nonmonotonic temperature dependence with a maximum at a nonzero temperature as well as a complex dependence on the twist angle at low temperatures. Effects of interface inhomogeneity are also discussed and demonstrated that they can drive topological to trivial superconducting transitions. Close to 45 degree twist we find that the critical current does not vanish due to Cooper pair cotunneling, which leads to a strong second harmonic in the current-phase relation and a putative transition to a time-reversal breaking topological superconducting phase. We show how the behavior of critical current in a magnetic field and under microwave drive can yield unambiguous evidence of Cooper pair cotunneling.
*P.A.V. is supported by a Rutgers Center for Material Theory Postdoctoral Fellowship and J.H.P. is partially supported by the Air Force Office of Scientific Research under Grant No. FA9550-20-1-0136, NSF CAREER Grant No. DMR-1941569, and the Alfred P. Sloan Foundation through a Sloan Research Fellowship. P.A.V. and J.H.P. acknowledge the Aspen Center for Physics where part of this work was performed, which is supported by National Science Foundation grant PHY-1607611. This work was partially supported by a grant from the Simons Foundation (P.A.V.). N.P. acknowledges the Deutsche Forschungsgemeinschaft (DFG452128813) for partial support with the project. P.K. acknowledges the support from the NSF (DMR-1809188) and S.Y.F.Z and X.C acknowledge the support from NSF (DMR-1922172).
