Pressure-induced linear enhancement of the superconducting transition in Nd_0.8Sr_0.2NiO₂ thin films

We report the pressure (P) effect on the superconducting transition temperature T-c and the upper critical field mu H-0(c2) of infinite-layer Nd0.8Sr0.2NiO2 thin films by measuring the electrical transport properties under various hydrostatic pressures to 4.6 GPa. At ambient pressure, it shows the clear superconducting transition with T-c similar to 10 K. Based on the evolution of resistance R(T), we found that the T-c is monotonically enhanced to similar to 14 K upon increasing pressure to 2.9 GPa. The constructed temperature-pressure phase diagram indicates that the calculated slope dT(c)/dP is about 1.14 K GPa(-1) and the superconducting T-c shows no signatures of saturation with pressure. It thus gives the possibility to further enhance T-c by employing higher pressures or heterostructure engineering. In addition, the normalized slope of upper critical field mu H-0(c2)(0) implies that the electron correlations are gradually decreasing with pressure, which exhibits an opposite evolution with superconducting T-c. Our work further confirms the positive pressure effects in nickelate superconductors and gives more insight to further enhance its superconducting transition temperature.