Superconductivity arising from layer differentiation in multilayer cuprates

Abstract

In order to theoretically identify the factors governing superconductivity in multilayer cuprates, a three-layer Hubbard model is studied with the two-particle self-consistent (TPSC) approach so as to incorporate electron correlations. The linearized Eliashberg equation is then solved for the gap function in a matrix form to resolve the role of outer CuO2 planes (OPs) and inner plane (IP). We show that OPs dominate IP in the dx2−y2-wave superconductivity, while IP dominates in the antiferromagnetism. This comes from an electron correlation effect in that the correlation makes the doping rates different between OPs and IP (i.e., a self-doping effect), which occurs in intermediate and strong correlation regimes. Namely, the antiferromagnetic fluctuations in IP are stronger due to a stronger electron correlation, which simultaneously reduces the quasiparticle density of states in IP with a suppressed dx2−y2-wave superconductivity. Intriguingly, while the off-diagonal (interlayer) elements in the gap function matrix are tiny, interlayer pair scattering processes are in fact at work in enhancing the superconducting transition temperature Tc through the interlayer Green's functions. This actually causes the trilayer system to have higher Tc than the single-layer in a weak- and intermediate-coupling regimes. This picture holds for a range of values of the on-site Hubbard repulsion U that contains those estimated for the cuprates. The present result is qualitatively consistent with nuclear magnetic resonance experiments in multilayer cuprate superconductors.

Source-reported materials — not catalogue approval

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