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

Abstract 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 (Tconset) over 40 K was achieved in La₃Ni₂O₇ and (La,Pr)₃Ni₂O₇ thin films at ambient pressure due to in-plane compressive strain. However, the Tc values in these thin films are still lower than that of the bulk bilayer nickelates under pressure. Here we report the enhancement of Tconset from about 40 K to over 60 K by applying hydrostatic pressure on the compressively strained bilayer nickelate thin films. The Tconset firstly ramps up with pressure, then it slightly drops down after reaching the maximum Tconset 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 Tc. Our theoretical calculations show that the increase of Tc 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 Tc through controlled manipulation of the electronic structure and interactions.