Two-band superconductivity through structural and electronic reconstruction on interface: YBa2Cu3O7/LaAlO3(001)

Novel physical phenomena arising from the complex interplay between the spin, charge, orbital, and lattice orders can emerge in perovskite-type oxide heterostructures. Here, we investigate the lattice and electronic structures on the interface of the YBa2Cu3O7/LaAlO3 heterostructure prepared by pulsed laser deposition with the combination of spherical aberration-corrected scanning transmission electron microscopy and density functional theory. Both reconstructed and normal interfaces are observed at sub-angstrom resolution, and these superconducting planes closest to the corresponding interface known as CuO2(a) and CuO2(c) planes, respectively. Due to the lattice reconstruction and charge density redistribution, CuO2(a) plane moves closer to the reconstructed interface with bond length of in-plane Cu and apical oxygen reduced. Consequently, the d3z2−r2 orbital loss electrons further results in two orbitals (dx2−y2 and d3z2−r2) crossing the Fermi level, showing two-band superconductivity behavior at the reconstructed interface. However, the CuO2(c) plane remains unaffected due to the protection of the charge reservoir layer at the normal interface and exhibits electronic structures similar to bulk cuprate superconductors, where only dx2−y2 orbitals contribute to the states at the Fermi level. These results suggest that the interfacial reconstruction might be a possible pathway to manipulate the electronic structures of the superconducting oxide heterostructures.