Traditionally, magnetism in solids deals with ordering patterns of the electron magnetic dipole moment, as probed, for instance, via neutron diffraction. However, materials such as f-electron heavy fermion systems are well-known candidates where more complex forms of symmetry breaking, involving higher-order magnetic or electric multipoles, are likely to be important. In this talk, I will discuss our recent theoretical proposal for Ising octupolar order in d-orbital systems, which appears to explain a wide range of experiments in certain 5d transition metal oxides with spin-orbit coupling. These include elastic neutron diffraction and X-ray diffraction, inelastic neutron scattering, and muon spin relaxation experiments. The proposed Ising ferro-octupolar order in these Mott insulators is linked to a specific type of uniform plaquette loop-current order. We propose NMR experiments under strain as further tests of our proposal. This appears to be the first clear candidate for octupolar order in a d-orbital system.

https://play.library.utoronto.ca/play/8ab99bf5199d0f6144975ebe165a61fb