Spin-Mediated Electron Pairing II

Raúl Oviedo‐Roa, C. Wang, Oracio Navarro

Ryotaro Arita, Kazuhiko Kuroki, Hideo Aoki

In order to identify the most favorable situation for superconductivity in the repulsive single-band Hubbard model, we have studied instabilities for d-wave pairing mediated by antiferromagnetic spin fluctuations and p-wave pairing mediated by ferromagnetic fluctuations with the fluctuation exchange approximation in both two dimensions and three dimensions. By systematically varying the band filling and band structure we have shown that (i) d pairing is stronger in two dimensions than in three dimensions and (ii) p pairing is much weaker than d pairing.

Anonymous, Feng Xu, Yuquan Xiang +11 more

Ming Lou

We investigate two exotic states in condensed matter: mesoscopic magnetism of integrable systems and Cooper pairing mediated by multiple-spin exchange.To study mesoscopic magnetism of integrable systems, we investigate, analytically and numerically, the orbital magnetism of free electron gas in a rectangular box, which is, classically, a model integrable system.We find that both the average orbital susceptibility and its fluctuations are determined by the two-level van Vleck susceptibility that involves the last occupied (Fermi) level and the first unoccupied level.This is in line with previous results for disordered (classically chaotic) systems.The mesoscopic fluctuations, however, are much larger in integrable systems and there is a pronounced non-self-averaging effect for phyical quantities in integrable systems.We find that, in units of µ 2 B /∆, where ∆ is the mean-level-spacing, the average orbital susceptibility isis the orbital angular momentum, N is the number of electrons in the box, and ε f -ε i is the level spacing (in units of ∆) between the last occupied level and the first unoccupied level.(ε f -ε i ) -1 is principally divergent and hence determined by the relevant cut-off.i

Douglas J. Scalapino

Sebastian Saner