Pressure-Tuned Superconductivity in FePSe3 Thin Films

Two-dimensional layered materials constitute a unique class of compounds in which strongly covalent or ionic atomic planes are stacked via van-der-Waals forces. This weak interlayer coupling allows the thickness to be precisely tuned down to few-layer or monolayer, giving rise to a rich spectrum of dimensionality-dependent physical properties. In this work, we take the prototypical van der Waals layered compound FePSe₃ as a model system and, by combining mechanical exfoliation with high-pressure techniques based on a diamond anvil cell (DAC), systematically investigate the electrical transport properties of both bulk FePSe₃ and thin layers with different thicknesses under pressure. We focus on the combined effects of external pressure and reduced dimensionality on the normal-state transport behavior and superconductivity. Experimental results show that bulk FePSe₃ exhibits pressure-tuned superconductivity, with the superconducting transition temperature <italic>T_c</italic> reaching a minimum around 15 GPa, accompanied by a concurrent minimum in the Hall coefficient <italic>R</italic>_H. This behavior is consistent with previous reports on bulk materials, and suggests that pressure may induce a Fermi surface reconstruction. Compared to the bulk, the thin-layer FePSe₃ samples show a suppressed superconducting state, characterized by a reduced <italic>T_c</italic>, and a monotonic decrease in <italic>R</italic>_H with increasing pressure. This indicates that two-dimensional confinement in thin flakes suppresses the occurrence of Fermi surface reconstruction. These findings provide key experimental evidence for understanding the pressure-driven evolution of the electronic states in FePSe₃.