Strain-tuning for superconductivity in La3Ni2O7 thin films

Abstract

The recent discovery of high-transition temperature (Tc) superconductivity in pressurized La3Ni2O7 bulk crystals has attracted keen attention for its characteristic energy diagram of eg orbitals containing nearly half-filled d3z2−r2 and quarter-filled dx2−y2 orbitals. This finding provides valuable insights into the orbital contributions and interlayer interactions in double NiO6 octahedrons that further provides a chance to control the electronic structure via varying ligand field. Here, we demonstrate that strain-tuning of the Tc over a range of 50 K with La3Ni2O7 films on different oxide substrates under 20 GPa. As the c/a ratio increases, the onset Tc systematically increases from 10 K in the tensile-strained film on SrTiO3 to the highest value about 60 K in the compressively strained film on LaAlO3. These systematic variations suggest that strain-engineering is a promising approach for expanding the superconductivity in bilayer nickelates with tuning the energy diagram for achieving high-Tc superconductivity.