Correlation-driven heavy-fermion formation in LiV2O4.

Optical reflectivity measurements were performed on a single crystal of the d-electron heavy-fermion (HF) metal LiV 2 O 4 . Our results evidence the highly incoherent charge dynamics above T* ≈ 20 K and the redistribution of the spectral weight of the optical conductivity over broad energy scales (∼5 eV) as the quantum coherence of the charge carriers is recovered. This reveals that LiV 2 O 4 is close to a correlation-driven insulating state and indicates that, in sharp contrast to f-electron HF Kondo-lattice systems, strong electronic correlation effects dominate the heavy quasiparticle formation in LiV 2 O 4 .