THE JAHN-TELLER EFFECT - AN INTRODUCTION AND CURRENT REVIEW

The Jahn-Teller effect (JTE) is defined and the historical background of the Jahn-Teller theorem is briefly discussed. The E x beta system, an electronic doublet coupled to a single mode of vibration, is introd uced as an elementary example and is used to illustrate features chara cteristic of Jahn-Teller systems. The spin resonance of Cu++ in variou s materials is considered and the particular case of Cu++ in a cubic c rystal field is used to introduce the E x epsilon Jahn-Teller system. The linear and quadratic E x epsilon systems are discussed, and the li near case is used to illustrate the appearance of the Berry phase in a quantum system. The role of the Jahn-Teller effect in high-temperatur e superconductivity is also discussed. In particular, the JTE-based su perconductivity theories of Englman et al. [Physica C 169, 314-324 (19 90)] and Weber et al. [Physica C 162/164, 307-312 (1989)] are briefly reviewed. The possible roles of the Jahn-Teller effect in C60 (buckmin sterfullerene) and superconducting K3C60 are also considered.