Weak- and strong-coupling expansions for the multi-band Hubbard model

✍ Scribed by J. Wagner; R. Putz; B. Ehlers; L. Lilly; A. Muramatsu; W. Hanke

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 123 KB
• Volume: 162-164
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(89)91272-0

✦ Synopsis

Pairing mediated by charge-transfer and magnetic fluctuations is examined for a two-component (d and p) Hubbard model in 2D with hopping (tnd),Short-range on-site (Ud,UD) and nearest-neighbor (Vc) repulsive interactions within (a) the randBm-phase approximation and (b) a strong coupling (tnd<E U d) expansion. In the weak-coupling regime the exchange of CDW modes leads to a superconductifig coupling constant for s-wave pairing (for Ud = O) which is rapidly suppressed and replaced by dwave pairing due to paramagnon exchange when simultaneously on-site repulsions are included. Similarly, in strong coupling, V c enhances the relative weight of s-versus d-wavepairing with the dominance of s-wave for large charge-transfer energy ~ and low to intermediate doping. Whereas in the large-& regime V c just enhances the magnetically driven pairing, for smaller A (~ 2tnH) a sizeable enhancement of the s-wave pairing due to the excitonic charge-transfer is observed. "-