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

TL;DR

Applying hydrostatic pressure to compressively strained bilayer nickelate thin films significantly raises their superconducting transition temperature (Tc), revealing a dome-like phase diagram and emphasizing the role of electronic correlations.

Contribution

This study demonstrates that pressure can enhance Tc in bilayer nickelate thin films beyond previous limits, highlighting the importance of electronic interactions and magnetic fluctuations.

Findings

Tc^onset increased to over 60 K under 9 GPa pressure

Superconducting Tc shows a dome-like dependence on pressure

Charge carriers are hole-like with increased density under 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 (Tc^onset) over 40 K was achieved in La3Ni2O7 and (La,Pr)3Ni2O7 thin films at ambient pressure due to in-plane compressive strain. This observation has sparked enormous attention because measurements on superconducting properties can be accessible with many commonly used experimental tools. On the other hand, the Tc in these thin films is much lower than that of the bulk bilayer nickelates under pressure. Here we report the enhancement of Tc^onset to over 60 K by applying hydrostatic pressure on the compressively strained superconducting bilayer nickelate thin films. The Tc^onset firstly ramps up with pressure, then it slightly drops down after reaching the maximum Tc^onset at about 61.5 K under a pressure of 9 GPa, showing a dome-like phase diagram. 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 results demonstrate that the enhancement of Tc arises from a cooperative amplification of magnetic fluctuations within and between the layers and increased metallicity under pressure. However, this enhancement exhibits saturation at higher pressures. 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.