Going from a good to a bad metal: signatures of resillient quasiparticles
Josef Stefan Institute, Ljubljana.
Mon, Dec. 17th 2012, 14:00
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
In metals with strong electron phonon coupling the resistivity as a function of temperature often saturates at the Mott-Ioffe-Regel (MIR) value, which corresponds to a scattering event each lattice spacing, and indicates the breakdown of the quasiparticle Boltzmann transport. In correlated metals, dominated by electron-electron interaction, the saturation does not occur, and associated poorly conducting metallic state was dubbed a bad metal. Does MIR criterion have a meaning for such metals? If it indicates a breakdown of quasiparticle picture, why is experimentally the Fermi liquid temperature below which resisivity is quadratic in temperature and susceptibility is Pauli two orders of magnitude lower than the MIR temperature? In the seminar I will present the novel insights we obtained to these questions by reconsidering a simple model system, a doped Hubbard model solved within dynamical mean-field theory using highly accurate quantum Monte Carlo and numerical renormalization group techniques. We find that the quasiparticles are remarkably resilient, they persists to temperatures well above the Fermi liquid temperature and all the way up to the MIR limit. The quasiparticle scattering is strongly particle-hole asymmetric, which has important consequences for thermopower. A high temperature bad metal state is associated with the extinction of quasiparticles, in a remarkable agreement with the simple MIR picture.