Interplay of the Jahn-Teller effect and spin-orbit coupling: The case of trigonal vibrations
S. V. Streltsov, Fedor Temnikov, K. I. Кugel, D. I. Khomskiǐ
Abstract
We study an interplay between the orbital degeneracy and the spin-orbit coupling (SOC) giving rise to spin-orbital entangled states in concentrated systems (cooperative Jahn-Teller [JT] effect). As a specific example, we analyze the interaction of electrons occupying triply degenerate single-ion ${t}_{2g}$ levels with trigonal vibrations (the $t\ensuremath{\bigotimes}T$ problem). A more general problem of the electron--lattice interaction involving both tetragonal and trigonal vibrations is also considered. It is shown that the result of such interaction crucially depends on the occupation of ${t}_{2g}$ levels leading to either the suppression or the enhancement of the JT effect by the SOC.