Dynamic Jahn-Teller effect in the strong spin-orbit coupling regime
Ivica Živković, Jian-Rui Soh, Oleg Malanyuk, Ravi Yadav, F. Pisani, Aria Mansouri Tehrani, Davor Tolj, Jana Pásztorová, Daigorou Hirai, Yuan Wei, Wenliang Zhang, C. W. Galdino, Tianlun Yu, Kenji Ishii, A. Demuer, Oleg V. Yazyev, Thorsten Schmitt, H. M. Rønnow
Abstract
Exotic quantum phases, arising from a complex interplay of charge, spin, lattice and orbital degrees of freedom, are of immense interest to a wide research community. A well-known example of such an entangled behavior is the Jahn-Teller effect, where the lifting of orbital degeneracy proceeds through lattice distortions. Here we demonstrate that a highly-symmetrical 5d1 double perovskite Ba2MgReO6, comprising a 3D array of isolated ReO6 octahedra, represents a rare example of a dynamic Jahn-Teller system in the strong spin-orbit coupling regime. Thermodynamic and resonant inelastic x-ray scattering experiments, supported by quantum chemistry calculations, undoubtedly show that the Jahn-Teller instability leads to a ground-state doublet, resolving a long-standing puzzle in this family of compounds. The dynamic state of ReO6 octahedra persists down to the lowest temperatures, where a multipolar order sets in, allowing for investigations of the interplay between a dynamic JT effect and strongly correlated electron behavior. Dynamic Jahn-Teller effect is rarely realized in condensed matter systems. Here, the authors demonstrate its occurrence in Ba2MgReO6, a 5d1 double perovskite, using resonant inelastic x-ray scattering, thermodynamic measurements and quantum chemistry calculations.