The possibility of the superconducting transition in the repulsive Hubbard model on a square lattice is studied using the ladder approximation of the strong coupling diagram technique. The t–U and t–t′–t″–U models are considered in the regime of strong correlations, for the on-site Coulomb repulsion U = 8t, in the range of temperatures 0.02t ≲ T ≲ 0.3t. To avoid the influence of the phase separation and size effects the calculations are performed in an infinite crystal, in the part of the phase diagram without inhomogeneities, for the electron concentration . Solutions of the Eliashberg equation for singlet and triplet pairing, which are transformed according to one-dimensional representations of the lattice point group D ₄, are considered. For both models and all considered symmetries, eigenvalues of the Eliashberg equation are less than unity and demonstrate no upward trend with decreasing temperature. This result points to the absence of superconductivity in the Hubbard model in the strong-coupling regime. We discuss the reason for the small eigenvalue of the Eliashberg equation in the case of the singlet pairing.

使用强耦合图技术的梯形近似研究了方形晶格上的排斥哈伯德模型中超导跃迁的可能性。所述吨- ù和吨-吨' -吨“ - ü模型是在强相关性的考虑制度，对于现场库仑排斥Ù = 8吨，在温度范围内0.02吨≲ Ť ≲0.3吨. 为了避免相分离和尺寸效应的影响，计算是在无限晶体中进行的，在相图中没有不均匀性的部分，对于电子浓度。考虑根据格点群D _{4 的}一维表示变换的单线态和三线态配对的 Eliashberg 方程的解。对于这两个模型和所有考虑的对称性，Eliashberg 方程的特征值都小于 1，并且随着温度的降低没有上升趋势。该结果表明在强耦合状态下哈伯德模型中不存在超导性。我们讨论了在单线态配对情况下 Eliashberg 方程的小特征值的原因。