Spin-orbital interplay in Jeff=3/2 Mott insulators

In d¹ Mott insulators, the spin-orbit coupling (SOC) stabilizes J_eff=3/2 quartet of an effective total angular momentum thus allowing for the emergence of multiorbital physics and related spin-orbital frustration. Considering vanadium, molybdenum, and osmium oxides as examples, I discuss how resulting spin-orbital interplay can give rise to a host of novel quantum phases that includes multipolar order, noncollinear spin patterns, and nonmagnetic disordered valence bond states. Finally, I present an example of the honeycomb lattice d¹ compound, such as zirconium trichloride, in which, paradoxically, the strong SOC enhances the symmetry of spin-orbital space to emergent SU(4) symmetric couplings that in turn may lead to a spin-orbital liquid state.