Optimally Tensile Strained La3Ni2O7 Films as Candidate High-Temperature Superconductors on Designer Substrates Ba1−xSrxO and SrO-Terminated SrTiO3

Abstract

High-temperature superconductivity in La3Ni2O7-derived films with critical temperatures (Tc) of 40–50 K has so far been realized only under substrate-induced compressive strain. Here we use first-principles calculations to predict that such La3Ni2O7 films can be stably grown on designer substrates Ba1−xSrxO (x=1–0) and SrO-terminated SrTiO3 (SrO−SrTiO3) with improved film quality and continuously tunable epitaxial strain, offering physically realistic materials platforms to achieve enhanced superconductivity. In particular, under the optimal tensile strain of ∼2% imposed by Ba0.75S0.25O or SrO−SrTiO3, the La3Ni2O7 films are energetically stable within a desirable thickness range, and more resilient against oxygen vacancy formation. Concomitantly, the lattice constant normal to the films is effectively reduced, and the Ni dz2 orbital is peaked near the Fermi level and hybridizes with the Ni dx2−y2 orbital, features that closely resemble their bulk counterparts at high pressure and strongly point to superconductivity with higher Tc. These findings establish innovative routes toward realizing enhanced superconductivity in tensile-strained La3Ni2O7 films, and allow to critically assess the role of the Ni dz2 orbital in superconducting pairing.

Source-reported materials — not catalogue approval

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