For Quantitative Estimation of Superconducting Temperature in Strongly Correlated Electron Systems

强相关电子系统中超导温度的定量估计

基本信息

批准号：
18540348
负责人：
YAMADA Kosaku
金额：
$ 0.79万
依托单位：
Ritsumeikan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

项目摘要

It is made dear that the superconducting transition temperature is determined by the following competing two effects.1. Renormalization of effective mass determines the band width of quasiparticles in Fermi liquid statesThe Coulomb interaction between electrons enhances the effective mass of electrons. The enhancement arises from the reduction of dispersion in electron bands. The renormalization factor z determines energy scale. For example, heavy electrons possesses 1000times large electron mass compared with free electron. Therefore the band width of quasiparticles is reduced by the factor of 1/1000 and takes the value around 10K On the other hand, the electron mass in cuprates is enhanced around 10 times and the band width of quasiparticles is reduced by 1/10 to 1000K. The superconducting gaps are created in these quasiparticle bands and renormalized by the inverse of quasiparticle mass, z. That is, the superconducting transition temperature is reduced in proportion to the wavefunction renormalization factor z. Thus the strong electron interaction reduces the transition temperature.2 . The momentum dependence of interaction between quasiparticles determines the symmetry and transition temperature of superconductivity.The isotropic repulsive force is canceled out by the sign change of gap function and the anisotropic parts of quasiparticle interaction determine the symmetry and transition temperature of superconducting state. In this case strong interaction increases the superconducting transition temperatureThe above two effects compete with each other. The former is determined by total interaction including isotropic part, while the latter is determined by dominant anisotropic momentum dependent part of quasiparticle interaction. As a result we can explain the transition temperature quantitatively. In strongly correlated electron systems.

很明显，超导转变温度是由以下两个相互竞争的效应决定的： 1．有效质量的重正化决定了费米液态中准粒子的带宽电子之间的库仑相互作用增强了电子的有效质量。这种增强是由于电子带色散的减少而产生的。重整化因子 z 决定能量尺度。例如，重电子拥有比自由电子大1000倍的电子质量。因此，准粒子的带宽减少了 1/1000，值为 10K 左右。另一方面，铜酸盐中的电子质量增强了 10 倍左右，准粒子的带宽减少了 1/10，达到 1000K 。超导能隙在这些准粒子带中产生，并通过准粒子质量的倒数 z 重新归一化。即，超导转变温度与波函数重正化因子z成比例地降低。因此强电子相互作用降低了转变温度。2．准粒子间相互作用的动量依赖性决定了超导态的对称性和转变温度。各向同性的斥力通过间隙函数的符号变化被抵消，准粒子相互作用的各向异性部分决定了超导态的对称性和转变温度。在这种情况下，强相互作用会提高超导转变温度。以上两种效应相互竞争。前者由包括各向同性部分的总相互作用决定，而后者由准粒子相互作用的主要各向异性动量依赖部分决定。因此我们可以定量地解释转变温度。在强相关电子系统中。