The Jahn-Teller effect and spin--orbit coupling: friends or foes?

TL;DR

This paper investigates how spin--orbit coupling influences the Jahn-Teller effect, revealing that quantum entanglement can either suppress, quench, or induce distortions depending on electron configurations, and can lead to complex energy surfaces.

Contribution

It demonstrates the significant impact of spin--orbit coupling on the Jahn-Teller effect, including conditions that quench, suppress, or induce distortions, and introduces the formation of a Mexican hat energy surface.

Findings

Spin--orbit coupling can quench Jahn-Teller distortions in certain configurations.

It can partially suppress Jahn-Teller effects depending on electron count.

Interplay with spin--orbit coupling can create a Mexican hat energy surface.

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.