Copyright © 2010 Hugo Keller and Annette Bussmann-Holder. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Recent experimental observations of unconventional isotope effects, multiband superconductivity, and unusual local lattice responses are reviewed and shown to be naturally explained within a two-component scenario where local polaronic effects are important. It is concluded that purely electronic mechanisms of high-temperature superconductivity are incomplete and unable to capture the essential physics of cuprates and other layered superconductors.