Fig. 5: Superconducting properties of Ca₂RuO₄ as a nanofilm.

a Band structure of Ca₂RuO₄ as a nanofilm using a FM order unfolded to primitive I4/mmm cell and projected on O (blue), Ca (green), Ru d_xy (red), d_xz+d_yz (grey) and d_x²_-y² and d_z² (orange) states. Majority (left panel) and minority (right panel) are reported. b Band splitting ∆E_g induced by freezing a displacement u_JTD (in Å/atom) associated with the JTD Q₂ -type mode in Ca₂RuO₄ nanofilm in the ground state with octahedral rotations (left panels) and without O₆ group rotations (right panels). c Evolution of ∆E_g as a function of the displacement u_JTD (in Å/atom) associated with the JTD Q₂ -type mode. The resulting Reduced Electron Phonon Matrix Element is estimated to D = 9.46 eV.Å⁻¹.d Total density of states (in states/eV/f.u/spin, grey area) as a function of the energy using the DFT calculation (lower part) and atomic-like Wannier functions (upper part). The WFs further allow to extract only contributions from the d_xz and d_yz orbitals (red line). The contribution from each d_xz or d_yz band is then of N(_F) = 0.31 states/eV/Ru/spin/band. The k-mesh is sampled with 12 x 12 x 4 points for the DFT calculation and with 256 x 256 x 64 points for the WFs. A ferromagnetic order is used throughout these calculations.