Pressure-induced linear enhancement of the superconducting transition in Nd_0.8Sr_0.2NiO₂thin films

We report the pressure (P) effect on the superconducting transition temperatureT_cand the upper critical fieldμ₀H_c2of infinite-layer Nd_0.8Sr_0.2NiO₂thin films by measuring the electrical transport properties under various hydrostatic pressures to 4.6 GPa. At ambient pressure, it shows the clear superconducting transition withT_c∼ 10 K. Based on the evolution of resistanceR(T), we found that theT_cis monotonically enhanced to ∼14 K upon increasing pressure to 2.9 GPa. The constructed temperature-pressure phase diagram indicates that the calculated slope dT_c/dPis about 1.14 K GPa^-1and the superconductingT_cshows no signatures of saturation with pressure. It thus gives the possibility to further enhanceT_cby employing higher pressures or heterostructure engineering. In addition, the normalized slope of upper critical fieldμ₀H_c2(0) implies that the electron correlations are gradually decreasing with pressure, which exhibits an opposite evolution with superconductingT_c. Our work further confirms the positive pressure effects in nickelate superconductors and gives more insight to further enhance its superconducting transition temperature.