Ambient pressure superconductivity in compressively strained (La,Pr)₃Ni₂O₇ thin films

Recently, high-temperature superconductivity has been discovered in bulk Ruddlesden-Popper nickelates under high pressure. This has motivated the pursuit to stabilize superconductivity in thin films at ambient pressure using epitaxial strain. Here we report progress in this direction. La₃Ni₂O₇, grown compressively strained on SrLaAlO₄ substrates, exhibits relatively fragile superconductivity, likely associated with the stacking defects observed [E. K. Ko et al., Nature DOI: 10.1038/s41586-024-08525-3 (2024)]. Much as for bulk samples, Pr substitution appears to stabilize the bilayer structure, and we observe significant enhancements in superconductivity for La₂PrNi₂O₇ [Y. Liu et al., arXiv:2501.08022]. Furthermore, the normal-state resistivity exhibits quadratic temperature dependence indicative of Fermi liquid behavior, and other phenomenological similarities to transport in overdoped cuprates suggest parallels in their emergent properties.



This work was done in collaboration with Eun Kyo Ko, Yijun Yu, Yidi Liu, Yaoju Tarn, Lopa Bhatt, Jiarui Li, Vivek Thampy, Cheng-Tai Kuo, Bai Yang Wang, Yonghun Lee, Kyuho Lee, Jun-Sik Lee, Berit H. Goodge, David A. Muller, and Srinivas Raghu. Work at SLAC/Stanford was primarily supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (Contract No. DE-AC02-76SF00515).