Quasiparticle properties in effective models for strongly correlated electrons

The single-hole states are studied by the exact diagonalization method in two models for strongly correlated systems: the single-band effective (t-J) model and the Kondo-lattice model. The coherent mass ${\mathit{m}}^{\mathrm{*}}$ of the quasiparticle and the frequency-dependent conductivity σ(ω) are calculated for clusters with 4×4 and 8×4 sites. In particular, σ(ω) shows an isolated quasiparticle peak of weak intensity at small ω and a broad but structured incoherent part at higher ω.