On superconductivity in (YBa2Cu3O7−δ)m/(PrBa2Cu3O7−δ)n superlattices. A quantitative analysis based on indirect-exchange pairing

摘要: Abstract We undertake a theoretical analysis of critical temperatures T C ( m , n ) observed in superlattices composed YBa 2 Cu 3 O 7− δ (YBCO) and, or alternating with, PrBa (PrBCO) unit cells, as function and . A survey suggested explanations, different phenomenological analyses based on Kosterlitz–Thouless transitions, proximity effects, charge transfer processes, shows that no conclusive interpretation these phenomena exists. Instead, we adopt microscopic approach indirect-exchange Cooper pairing between conduction electrons (quasi-particles) via oxygen anions. On this basis, due to structural electronic similarities the components, an YBCO/PrBCO supercell is treated “extended” YBCO system. Assuming only cell adjacent PrBCO (electronically) directly affected upon forming supercell, essential agreement with experiment obtained for all values without any parameter adjustment. In conformity results conductance experiments by Cieplak et al. (Phys. Rev. B 50 (1994) 12 876) establish direct correlation normal-state property system, Fermi vector length k F The do not support (widespread) assumption interlayer (intercell) coupling neither -YBCO units nor intercell within same unit.