An orbital-selective spin liquid in a frustrated heavy fermion spinel LiV$_2$O$_4$

摘要

The pronounced enhancement of the effective mass is the primary phenomenonassociated with strongly correlated electrons. In the presence of localmoments, the large effective mass is thought to arise from Kondo coupling, theinteraction between itinerant and localised electrons. However, in d electronsystems, the origin is not clear because of the competing Hund's rule coupling.Here we experimentally address the microscopic origin for the heaviest dfermion in a vanadium spinel LiV2O4 having geometrical frustration. Utilisingorbital-selective 51V NMR, we elucidate the orbital-dependent local moment thatexhibits no long-range magnetic order despite persistent antiferromagneticcorrelations. A frustrated spin liquid, Hund-coupled to itinerant electrons,has a crucial role in forming heavy fermions with large residual entropy. Ourmethod is important for the microscopic observation of the orbital-selectivelocalisation in a wide range of materials including iron pnictides, cobaltates,manganites, and ruthnates.