The band Jahn–Teller effect: A new perspective on an old problem

Using the example of a cubic crystal with linear E ⊗ e coupling in every elementary cell, we present the specifics of elementary excitations in a conductor with the band Jahn–Teller (JT) effect above the temperature of structural phase transition. We explore the dynamics of JT-coupled electrons in a partly filled valence band in the simplest case of weak vibronic coupling to one dispersionless optical phonon band. Maximum JT hybridization of electron and phonon states takes place in the avoided crossing part of the energy spectrum where the electron and the phonon branches come close to one another and the electron density of states manifests a pseudo-gap. Most interesting effects occur when doping brings Fermi level to the resonance energy. Also, the band JT effect results in a non-linear temperature dependence of electron specific heat which can be interpreted as non-Fermi-liquid behavior.