Dynamic Jahn-Teller Phenomena in Heavy Transition Metal Compounds

This paper reviews recent experimental and theoretical developments of the dynamic Jahn-Teller effect-driven phenomena in heavy transition metal-based spin-orbit Mott insulators. In cubic $4d/5d$ transition metal compounds, the spin, orbital, and lattice degrees of freedom can form quantum entanglement on metal sites and induce unconventional quantum phenomena. Fingerprints of orbital-lattice entanglement called the dynamic Jahn-Teller effect appear in spectroscopic data such as resonant inelastic x-ray scattering spectra. In cubic $5d^1$ compounds with the fcc structure, the dynamic Jahn-Teller states on metal sites behave cooperatively and exhibit rich ordered phases.