Jahn-Teller Effect and Spin-Orbit Coupling: Friends or Foes?

Abstract

The Jahn-Teller effect is one of the most fundamental phenomena important not only for physics but also for chemistry and material science. Solving the Jahn-Teller problem and taking into account strong electron correlations we show that quantum entanglement of the spin and orbital degrees of freedom via spin-orbit coupling strongly affects this effect. Depending on the number of d electrons, it may quench (electronic configurations t_{2g}^{2}, t_{2g}^{4}, and t_{2g}^{5}), partially suppress (t_{2g}^{1}), or, in contrast, induce (t_{2g}^{3}) Jahn-Teller distortions. Moreover, in certain situations, interplay between the Jahn-Teller effect and spin-orbit coupling promotes formation of the “Mexican hat” energy surface facilitating various quantum phenomena.