Observation of orbital fluctuation inducing unconventional magnetic order in a correlated insulator

Intertwined electronic and orbital degrees of freedom in strongly correlated materials with strong spin-orbit-coupling has shown to give rise to many exotic quantum phenomenon, especially to emergent quantum phases and transitions ^[1,2], such as quantum spin liquids, multipolar orderings, cooperative Jahn-Teller (JT) effects, and correlated topological semi-metals. 4d and 5d transition metal compounds have provided a rich playground for realizing these correlated quantum phenonmenon. In these materials, it is often difficult to determine the driving mechanism for the emergent phases. Here we implement a multi-modal technique ^[3] that is able to independently probe different symmetry-related order parameters to determine the primary driving order parameter in such a system. Examples of the application of the technique to real materials will be discussed.

[1] Witczak-Krempa, William, et al. "Correlated quantum phenomena in the strong spin-orbit regime." Annu. Rev. Condens. Matter Phys. 5.1 (2014): 57-82.

[2] Chen, Gang, Rodrigo Pereira, and Leon Balents. "Exotic phases induced by strong spin-orbit coupling in ordered double perovskites." Physical Review B 82.17 (2010): 174440.

[3] Carr, Stephen, et al. "Multi-modal spectroscopy of phase transitions." arXiv preprint arXiv:2208.10987 (2022).