Mott transition and heavy-fermion state in the pyrochlore Hubbard model

We investigate the interplay between geometrical frustration and strong electron correlation based upon the pyrochlore Hubbard model. In the half-filling case, using the perturbative expansion in terms of electron correlation, we show that the self-energy shows a divergent behavior leading the system into the Mott insulating state, in which a quantum disordered spin liquid without magnetic long-range order is realized. In the hole-doped case, we obtain heavy-fermion-like Fermi-liquid state. We also calculate the neutron cross section, which is very consistent with recent neutron scattering experiments for itinerant pyrochlore systems.