Pseudogap phenomena and phase diagram in the two-band Hubbard model

Citation
A. Kobayashi et al., Pseudogap phenomena and phase diagram in the two-band Hubbard model, J PHYS JPN, 70(5), 2001, pp. 1214-1217
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
ISSN journal
0031-9015 → ACNP
Volume
70
Issue
5
Year of publication
2001
Pages
1214 - 1217
Database
ISI
SICI code
0031-9015(200105)70:5<1214:PPAPDI>2.0.ZU;2-Q
Abstract
High-T-C superconducting materials (HTSC) have anomalous properties such as the pseudogap in the Hall coefficient. 1/T1T and the density of states etc . First, including the effects of strong on-site repulsion between d-electr ons at Cu-sites. we obtain quasi-particles with superexchange interaction J (s), whose band-width tends to reach zero. i.e., the system goes to the ins ulator, as delta tends to reach zero. The quasi-particles correspond to Zha ng nice singlet states. J(s) larger than the band width combined with the t wo-dimensional characteristic of the system induces strong antiferromagneti c fluctuations (AFF) and superconducting fluctuations ISC:F). We treat effe cts of the AFF in the FLEX approximation and those of the SCF in the self-c onsistent t-matrix approximation to show that both fluctuations in the unde rdoped region start to increase at T-0 as T decreases from T much greater t han T-C. and that the AFF dominate the SCF at T > T-sg while the SCF domina te at T < T-sg. This cross-over of the fluctuations causes the anomalous ph enomena in the underdoped region. We also obtain the T - delta phase diagra m of HTSC consistent with the one observed in experiments.