Sarker Sanjoy K, Lair Samuel L
Department of Physics, The University of Alabama, Tuscaloosa, AL 35487, USA.
J Phys Condens Matter. 2005 Jun 29;17(25):3885-94. doi: 10.1088/0953-8984/17/25/015. Epub 2005 Jun 10.
It is shown that a metal-insulator transition can occur far from half-filling in the negative-U Hubbard model in the presence of long-range repulsive interactions. Specifically, we consider the bcc lattice at an electron concentration of 2/3 and show that a CDW insulating state exists which is energetically favoured over the relevant metallic states. The repulsive interaction plays the same role as it does in stabilizing a Wigner crystal. Despite the absence of Fermi surface nesting, the CDW insulator appears at rather small values of the interaction, preceded by a CDW semimetal at even smaller values. This places severe restrictions on the region of the parameter space where superconductivity may exist. We believe that the model will show similar behaviour for other electron densities and other lattices.
结果表明，在存在长程排斥相互作用的情况下，负U哈伯德模型中远离半填充时会发生金属-绝缘体转变。具体而言，我们考虑电子浓度为2/3的体心立方晶格，并表明存在一种电荷密度波（CDW）绝缘态，其能量上比相关金属态更有利。排斥相互作用在稳定维格纳晶体中所起的作用相同。尽管不存在费米面嵌套，但CDW绝缘体在相当小的相互作用值时出现，在更小的值时会出现CDW半金属。这对可能存在超导性的参数空间区域施加了严格限制。我们相信该模型对于其他电子密度和其他晶格将表现出类似行为。
