Optimization variational Monte Carlo study of the crossover between BCS state and Bose-Einstein condensate

将一个包含排斥关联因子和近邻吸引关联因子的试探波函数应用到吸引Hubbard模型中，证实了在中等关联强度下超导能隙的大小最大.同时，通过交叉区，超导电性的性质发生了变化。在排斥模型作为铜氧化物超导体的模型中，观察到类似的交叉作为电子密度的函数，显示出与吸引模型的相似性。

Applying a trial wave function with onsite repulsive and near-neighbor doublon-holon attractive correlation factors to the attractive Hubbard model, we confirmed that the magnitude of the superconducting gap becomes the largest in the intermediate correlation strength. At the same time, the character of superconductivity changes through the crossover region. In the repulsive model as a model of cuprate superconductors, similar crossover is observed as a function of electron density, showing the similarity with the attractive model.