Field-Induced Kitaev Multipolar Liquid in d² Honeycomb Mott Insulators

Kitaev's spin-1/2 honeycomb model, featuring compass-like Ising interactions, has demonstrated the central role of bond-dependent frustration in generating exotic phases of matter. Such interactions appear naturally between the spin-orbit entangled dipole moments of several d⁵ and d⁷ Mott insulators, although the dominance of the Kitaev physics relative to other effects remains a topic of debate. Motivated by compass interactions among quadrupole moments in 5d² Mott insulators, we provide a route to uncovering the Kitaev multipolar liquid, where it is the non-Kramers doublets carrying multipole moments that are fractionalized into Majorana fermions. The key ingredient is the magnetic field which allows for quadrupole-octupole interactions via mixing with the excited triplet states. The conditions to realize signatures of this phase in real materials are also discussed.