Heavy fermions in the transition-metal compoundLiV2O4

Lithium vanadate is a heavy-fermion metal with a mass enhancement of ${O(10\mathrm{}}^2)$ while its isostructural neighbor, lithium titanate, has a mass enhancement of only O(1). The Hamiltonian for them as well as for the manganites (which are ferromagnetic metals) are the same except for a change of the spins of the magnetic ions. The enormous difference in the properties of these compounds raises some puzzling questions about strongly correlated fermions. These are discussed and a solution is provided.