Bünemann Jörg, Gebhard Florian, Radnóczi Katalin, Fazekas Patrik
Fachbereich Physik, Philipps-Universität Marburg, D-35032 Marburg, Germany.
J Phys Condens Matter. 2005 Jun 29;17(25):3807-14. doi: 10.1088/0953-8984/17/25/007. Epub 2005 Jun 10.
We investigate the electronic and superconducting properties of a negative-U Hubbard model. For this purpose we evaluate a recently introduced variational theory based on Gutzwiller-correlated BCS wavefunctions. We find significant differences between our approach and standard BCS theory, especially for the superconducting gap. For small values of |U|, we derive analytical expressions for the order parameter and the superconducting gap which we compare to exact results from perturbation theory.
我们研究了负U哈伯德模型的电子和超导特性。为此，我们评估了一种最近基于古兹维勒关联BCS波函数引入的变分理论。我们发现我们的方法与标准BCS理论之间存在显著差异，特别是在超导能隙方面。对于|U|的小值，我们推导了序参量和超导能隙的解析表达式，并将其与微扰理论的精确结果进行比较。
