Pressure-Induced Structural and Semiconductor-Metal-Superconductor Transitions in a High-Entropy van der Waals Compound (MnFeCuCdIn)PSe₃

The properties of the emerging phosphochalcogenide compounds can be tuned by temperature, pressure, and the chemical composition characterized by the compound entropy. However, it is unknown how the entropy of such a compound affects its structural stability and material properties when a state variable changes. In this work, a new layered high-entropy phosphoselenide compound (MnFeCuCdIn)PSe₃ (denoted MPSe₃) is prepared and its structural evolution and property changes are studied at pressures up to ≈60 GPa. It is found that the compound undergoes two isostructural changes at ≈10 and 20 GPa, a structural change forming a high-coordination phase in ≈32–35 GPa, a semiconductor-to-metal transition in ≈28–30 GPa at room temperature, and a metal-to-superconductor transition in ≈2.5–4.9 K at a pressure from ≈43 to 58 GPa. Combining data from prior studies, it is further found that for the MPSe₃-type medium/high-entropy compounds, there exists a linear relationship between the structural transition pressure and the cation mixing entropy, and an inverse nearly linear relationship between the superconducting critical temperature and the cation mixing entropy, with the latter due primarily to the decrease in the Debye temperature. These findings will have great importance for developing new complex materials using the evolving entropy engineering.