Pressure-induced structural transitions and metallization in ZrSe₂

High-pressure studies of two-dimensional materials have revealed numerous novel properties and physical mechanisms behind them. As a typical material of transition metal dichalcogenides (TMDs), ZrSe₂ exhibits high carrier mobility, rich electronic states regulated by doping, and high potential in applications at ambient pressure. However, the properties of ZrSe₂ under pressure are still not clear, especially for the structural and electrical properties. Here, we report the investigation of ZrSe₂ under pressure up to 66.5 GPa by in-situ x-ray diffraction, Raman, electrical transport measurements, and first-principles calculations. Two structural phase transitions occur in ZrSe₂ at 8.3 GPa and 31.5 GPa, from P-3m1 symmetry to P2₁/m symmetry, and finally transformed into a non-layer I4/mmm symmetry structure. Pressure-induced metallic transition is observed at around 19.4 GPa in phase II which aligns well with the results of the calculation. Our work will help to improve the understanding of the evolution of the structure and electrical transport properties of two-dimensional materials.