Theoretical models of high-T[sub(c)] oxides

Knowledge of the mechanism of pairing of carriers and of the nature of the normal state is central to an understanding of the high-Tc supeconductivity in metal oxides (Bednorz and Muller (1986)) and in doped fullerenes (MXC60) (Hebard et al. (1991), Holczer et al. (1991)). Superconductivity is a correlated many body state of pairs which is well described by the BCS theory in the weak-coupling limit A < 1. Depending on the specific bosonic field, which 'glues' two carriers together, the BCS superconductor could be not only 'phononic' but also 'excitonic' (Little (1964), Ginzburg (1968)), 'plasmonic' (Frohlich (1968), Pashitskii (1968)), or 'magnonic (quasi)' (Schrieffer et al. (1989), Millis et al. (1990), Wood and Cooke (1992), Kamimura et al (1992), Monthoux and Pines (1992)) (see left hand side of Fig. 6.1).