Well defined phase boundaries and superconductivity with high T_c in PbSe single crystal

Lead chalcogenides represent a significant class of materials that exhibit intriguing physical phenomena, including remarkable thermoelectric properties and superconductivity. In this study, we present a comprehensive investigation on the superconductivity of PbSe single crystal under high pressure. The signature of superconducting (SC) transition starts to appear at 7.2 K under 16.5 GPa. Upon further compression, the SC temperature (T_c) decreases, and it is reduced to 3.5 K at 45.0 GPa. The negative pressure dependent behavior of T_c is consistent with the trend of T_c–P relations observed in other lead chalcogenides. The highest T_c is 8.0 K observed at 20.5 GPa during decompression process, which is also the highest record among all other PbSe derivatives, such as doped samples, superlattices, and so on. The phase boundaries of the structural and electronic transitions are well defined by Raman spectroscopy, and then phase diagrams are plotted for both compression and decompression processes. This work corrects the previous claim of positive pressure dependence of T_c in PbSe and provides clear phase diagrams for intrinsic superconductivity in PbSe under pressure.