High-Pressure Electrical Transport Measurements on 2H-NbSe₂ Thin Films

Ultrathin 2H-NbSe₂ exhibits a unique interplay of an enhanced charge density wave (CDW) and Ising-type superconductivity, making it a promising candidate for quantum tuning studies. Hydrostatic pressure, applied via diamond anvil cells (DACs) is widely employed to explore the physical properties of materials. However, high-pressure measurements have never been performed on NbSe₂ thin films due to the technical challenges associated with transport measurements in DACs. Here, we introduce a technique combining pre-patterned electrodes and a dry-transfer process to enable precise electrical transport measurements on two-dimensional (2D) materials under pressure. Using this approach, we measured resistance, magnetoresistance, and Hall effect in NbSe₂ thin films under high pressure. The CDW transition temperature (T_CDW) is enhanced compared to the bulk NbSe₂, verifying the ultrathin nature of the samples. Despite the enhanced T_CDW in thin films, the CDW order vanishes near ∼ 5 GPa, similar as the bulk NbSe₂. In addition, two superconducting regions are observed in thin film NbSe₂ under pressure, with the optimal superconducting transition temperature (T_c) achieved near ∼ 5 GPa, significantly lower than the pressure required in bulk samples. The CDW ending at the maximum T_c suggests that the superconducting order in ultrathin NbSe₂ competes with CDW order. Our work establishes a novel method for electrical transport measurements in nanometer-thin films under pressure and reports the first high-pressure data on thin-film NbSe₂, shedding new insights on the interplay of competing orders in 2D quantum materials.