Theoretical Study of Kondo lattices by the 1/d expansion method

在过去的16年里，我发展了近藤晶格的理论; 1987年发表的高温超导的一个新理论也在这个理论框架内。（1）巡回电子铁磁性：当Hund耦合足够强时，对于多带模型，超交换相互作用可以是铁磁性的。当化学势位于能带边缘之一时，特别是当态密度出现尖峰时，由准粒子对激发的虚交换产生的交换相互作用也可以是铁磁的。这两种交换作用是造成巡回选举系统铁磁性的主要原因。（2）巡游电子反铁磁体的磁结构：当存在等效嵌套矢量时，可以稳定多个Q自旋密度波（SDW）态;对于双Q或三Q SDW，不同Q的磁化强度应该相互正交。（3）高温超导体正常态的赝能隙：由于准粒子的寿命宽度较大，可以出现各向异性赝能隙，这主要是由dγ波超导涨落引起的。（4）高温超导体中的电子-声子相互作用：我提出了一种新的电子-声子相互作用，它是由声子对超交换相互作用的调制引起的。这种电子-声子相互作用可以解释准粒子色散和声子软化的扭结。（5）无序Kondo晶格中的Mott-Hubbard金属-绝缘体交叉：如果空穴掺杂的铜氧化物的无序度比电子掺杂的铜氧化物的无序度大，那么空穴掺杂的铜氧化物和电子掺杂的铜氧化物之间交叉的不对称性可以用无序Kondo晶格理论来解释。

I have developed a theoiy of Kondo lattices for past 16 yeais ; an eaily theoiy of high-temperature superconductivity published in 1987 is also within this theoretical framework. I have applied the theory to the following five issues on strong election correlations : (1)Itinerant-electron ferromagnetism : The supeiexchange interaction can be ferromagnetic for multi-band models, when the Hund coupling is strong enough. The exchange interaction arising from the virtual exchange of pair excitations of quasiparticles can also be ferromagnetic, when the chemical potential is at one of the band edges, in particular, when a sharp peak of the density of states is there. These two exchange interactions are mainly responsible for ferromagnetism in itinerant-election systems. (2)Magnetic structures of itinerant-electron antiferromagnets : When there are equivalent nesting vectors, multiple Q spin density wave (SDW) states can be stabilized ; magnetizations with different Q should be orthogonal to each other for double or triple Q SDW. (3)Pseudogaps in normal states of high-temperature superconductors : Anisotropic pseudogaps can appear because of large life-time widths of quasiparticles, which are mainly caused by dγ-wave superconducting fluctuations. (4)Election-phonon interaction in high-temperature superconductors : I have proposed a novel electron-phonon interaction arising from the modulation of the superexchange interaction by phonons. This election-phonon interaction can explain kinks in the quasiparticle dispersion and the softening of phonons m cuprates. (5)Mott-Hubbard metal-insulator crossover in disordered Kondo lattices : The asymmetry of the crossovei between hole-doped and electron-doped cuprates can be explained by a theory of disordered Kondo lattices, if disorder of hole-doped cuprates is relatively larger than that of election-doped cuprates.