DYNAMIC JAHN-TELLER COUPLING, ANHARMONIC OXYGEN VIBRATIONS AND HIGH-Tc SUPERCONDUCTIVITY IN OXIDES
- 1 December 1989
- journal article
- review article
- Published by World Scientific Pub Co Pte Ltd in Modern Physics Letters B
- Vol. 03 (18) , 1367-1374
- https://doi.org/10.1142/s0217984989002065
Abstract
A universal dynamic Jahn-Teller (DJT) mechanism for superconductivity and its applications to CuO and BaBiO 3 high-T c oxides are reviewed. Dynamical interconversion between the shallow "double-well" potentials of degenerate delocalized oxygen-oxygen "pπ-bonds" at the Fermi energy (E F ) induces anharmonic oxygen vibrations, lattice-electron coupling, and Cooper pairing. This mechanism yields high T c 's and small-to-vanishing isotope shifts for cuprates, where O (pπ)- O (pπ) bond overlap at E F is promoted by Cu (dπ*)- O (pπ) hybridization. It yields lower T c 's and larger isotope shifts for BaBiO 3's, where O (pπ)- O (pπ) overlap is small. For vanishing bond overlap at E F , DJT coupling reduces to harmonic phonon coupling in BCS theory. Simple formulae for calculating T c and isotope shifts for any superconductor from the "real-space" chemical bonding at E F are presented, yielding (T c ) max ≈ 230 K .Keywords
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