Strain-tuning for superconductivity in La3Ni2O7 thin films

Abstract

Abstract The recent discovery of high-transition temperature (T c) superconductivity in pressurized La3Ni2O7 bulk crystals has attracted keen attention for its characteristic energy diagram of e g orbitals containing nearly half-filled $${d}_{{3}{z}^{2}-{r}^{2}}$$ d 3 z 2 − r 2 and quarter-filled $${d}_{{x}^{2}-{y}^{2}}$$ d x 2 − y 2 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 T c over a range of 50 K with La3Ni2O7 films on different oxide substrates under 20 GPa. As the c/a ratio increases, the onset T c 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-T c superconductivity.