Vibronic transitions ordered perovskites

Already in the seminal paper of Bednorz and Muller [1], the guide to look for systems with a high superconductive transition temperature (Tc), has been the presence of strong electron-phonon interactions. Such interaction has been known to exist in a wide class of perovskite type oxides. The authors mention [1] the vibronic Jahn-Teller polaron effect [2] in this context. They also emphasize the fact that the Cu2+-ion is a well-known Jahn-Teller system and this circumstance preserves significance in the physics of cuprate superconductors [3-7]. As a microscopic cause for ferroelectric ordering the interband vibronic hybridisation has been supposed [8-11] enlargening the view on perovskites as Jahn-Teller systems. 

---