Yidi Liu

All Publications

• Superconductivity and normal-state transport in compressively strained La2PrNi2O7 thin films. Nature materials Liu, Y., Ko, E. K., Tarn, Y., Bhatt, L., Li, J., Thampy, V., Goodge, B. H., Muller, D. A., Raghu, S., Yu, Y., Hwang, H. Y. 2025

  Abstract

  The discovery of superconductivity under high pressure in Ruddlesden-Popper phases of bulk nickelates has sparked great interest in stabilizing ambient-pressure superconductivity in the thin-film form using epitaxial strain. Recently, signs of superconductivity have been observed in compressively strained bilayer nickelate thin films with an onset temperature exceeding 40 K, although with broad, two-step-like transitions. Here we report the intrinsic superconductivity and normal-state transport properties in compressively strained La2PrNi2O7 thin films, achieved through a combination of isovalent Pr substitution, growth optimization and precision ozone annealing. The superconducting onset occurs above 48 K, with zero resistance reached above 30 K, and the critical current density at 1.4 K is 100-fold larger than previous reports. The normal-state resistivity exhibits quadratic temperature dependence indicative of Fermi liquid behaviour, and other phenomenological similarities to transport in overdoped cuprates suggest parallels in their emergent properties.

  View details for DOI 10.1038/s41563-025-02258-y

  View details for PubMedID 40442446

  View details for PubMedCentralID 10951943

• Signatures of ambient pressure superconductivity in thin film La3Ni2O7. Nature Ko, E. K., Yu, Y., Liu, Y., Bhatt, L., Li, J., Thampy, V., Kuo, C. T., Wang, B. Y., Lee, Y., Lee, K., Lee, J. S., Goodge, B. H., Muller, D. A., Hwang, H. Y. 2024

  Abstract

  Recently, the bilayer nickelate La3Ni2O7 has been discovered as a new superconductor with transition temperature Tc near 80 K under high pressure1-3. Despite extensive theoretical and experimental work to understand the nature of its superconductivity4-29, the requirement of extreme pressure restricts the use of many experimental probes and limits its application potential. Here, we present signatures of superconductivity in La3Ni2O7 thin films at ambient pressure, facilitated by the application of epitaxial compressive strain. The onset Tc varies approximately from 26 K to 42 K, with higher Tc values correlating with smaller in-plane lattice constants. We observed the co-existence of other Ruddlesden-Popper phases within the films and dependence of transport behavior with ozone annealing, suggesting that the observed low zero resistance Tc of around 2 K can be attributed to stacking defects, grain boundaries, and oxygen stoichiometry. This finding initiates numerous opportunities to stabilize and study superconductivity in bilayer nickelates at ambient pressure, and to facilitate the broad understanding of the ever-growing number of high temperature and unconventional superconductors in the transition metal oxides.

  View details for DOI 10.1038/s41586-024-08525-3

  View details for PubMedID 39701131