Structural modifications in strain-engineered bilayer nickelate thin films

Key Points:

• High-temperature superconductivity in La3Ni2O7 has been observed under high hydrostatic pressure and biaxial compression in thin films, sparking interest in the relationship between atomic and electronic structures in these materials.
• Subtle changes in nickel-oxygen bonding are believed to be crucial for stabilizing superconductivity, but the exact bonds and modifications involved have remained unclear.
• Using multislice electron ptychography, researchers directly measured atomic-scale structural changes in La3Ni2O7 thin films under varying biaxial strains, revealing how specific atomic bond evolutions relate to superconductivity.
• The study identifies that compressive strain induces nickel-oxygen octahedral distortions that lift crystalline symmetry, a key factor for superconductivity, and notes that in-plane lattice compression is common to both bulk and thin film superconducting states.
• A new theoretical framework was developed to analyze structural distortions in corner-sharing octahedra, suggesting that both hydrostatic pressure and compressive strain enhance superconductivity by suppressing t2g orbital mixing through increased octahedral symmetry.