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

The discovery of high temperature superconductivity in the nickelate system has stimulated enormous interest in the community of condensed matter physics. Recently, superconductivity with an onset transition temperature ( T _c ^onset ) over 40 K was achieved in La ₃ Ni ₂ O ₇ and (La _, Pr) ₃ Ni ₂ O ₇ thin films at ambient pressure due to in-plane compressive strain. However, the T _c values in these thin films are still lower than that of the bulk bilayer nickelates under pressure. Here we report the enhancement of T _c ^onset from about 40 K to over 60 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 61.5 K. Hall effect measurements reveal that the dominant charge carriers are hole-like with a slight enhancement of charge carrier density with pressure in accompanying with the increase of T _c . Our theoretical calculations show that the increase of T _c may be caused by a cooperative enhancement of magnetic fluctuations within and between 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.