Abstract
The domains and domain boundaries in 2D materials are known to play essential roles in investigating intriguing physical properties and have potential applications in nanoscale devices. Understanding the influence of individual domains on the superconducting properties of ultrathin 2D superconductors is of crucial importance for fundamental studies on mesoscopic superconductivity as well as applications in superconducting nanoelectronics. Here, low-temperature electronic transport measurements of high quality ultrathin Mo2C crystals are presented that show clear evidence for the presence of multiple superconducting phase induced by the nanoscale domain structures. In particular, the observation of an anomalous resistance peak in the vicinity of the onset of the superconducting transition is reported. This resistive anomaly is interpreted as a consequence of nonequilibrium charge imbalance near the domain boundaries, which could induce effective normal-superconducting interfaces in 2D Mo2C crystals. Moreover, the magnetic field-tuned superconductor-metal transition for ultrathin Mo2C crystals is examined. The observed scaling behavior is consistent with the appearance of quantum Griffiths singularity in 2D superconducting systems. This study sheds light on the understanding of the domain boundaries and their role on the transport properties of highly crystalline 2D superconductors, which may open potential application of domain structure in functional superconducting nanodevices.