Enhanced superconductivity in the compressively strained bilayer nickelate thin films by pressure

Recently, superconductivity with onset transition temperature (T_c^onset) over 40 K was achieved in La₃Ni₂O₇ and (La_,Pr)₃Ni₂O₇ thin films at ambient pressure due to in-plane compressive strain. However, the T_c in these thin films are lower than that of the bulk bilayer nickelates under pressure. Here we report the enhancement of T_c^onset from about 30 K to over 48 K by applying hydrostatic pressure on the compressively strained bilayer nickelate thin films. The T_c^onset firstly ramps up with pressure, then it slightly drops down after reaching the maximum T_c^onset at about 48.5 K. Our theoretical calculations yield a cooperative enhancement of magnetic fluctuations between and within the layers and increased metallicity under pressure. These findings highlight the critical role of the interplay between interlayer and intralayer electronic correlations in bilayer nickelate superconductors and point to the potential of tuning T_c through controlled manipulation of the electronic structure and interactions.