Proximity-induced time-reversal symmetry breaking superconductivity in a transition metal dichalcogenide

Local non-centrosymmetry in materials can lead to staggered spin-orbit coupling with interesting properties such as layer-dependent spin momentum locking, which is hidden within the system. In the context of superconductivity, this structural property can have more profound implications and lead to the formation of unconventional superconducting order parameters in the system beyond the conventional s-wave superconducting order parameter. In this work, we establish the presence of a proximity-induced time-reversal symmetry breaking order parameter in a Josephson junction constructed from a two-dimensional van der Waals transition metal dichalcogenide. We observe a large asymmetry in critical currents of the junction in zero applied magnetic fields, the sign of which switches upon reversing the sweep direction of the magnetic field leading to a clear magnetic hysteresis in the observed asymmetry which has been reported so far only in ferromagnetic Josephson junctions. This observation of a possible time-reversal symmetry breaking topological superconducting state in an air-stable van der Waals system provides a new and flexible avenue for research on topological superconductivity.