Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 38: Correlated Electrons: Metal-Insulator Transition 1
TT 38.3: Vortrag
Mittwoch, 13. März 2013, 10:00–10:15, H20
Nanodomain formation and electronic transport near the 1st-order Mott-Hubbard transition — Qinyong Liu and •Johann Kroha — Physikalisches Institut, Universität Bonn
In the vicinity of the 1st-order metal-insulator transition (MIT) in Mott-Hubbard systems metallic and insulating phases coexist. Since the MIT occurs not only at temperature T=0, but persists to finite T, in the coexistence region the thermodynamically stable state consists of thermal excitations of insulating nanodomains within the metal and vice versa. The existence of such nanodomains has been demonstrated experimentally in VO2. We calculate the size distribution of nanodomains as a function of T and Hubbard repulsion U. To that end, the electronic spectra and the free energy per site are determined in metallic and in insulating regions as well as across a metal-insulator domain wall, using the generalization of dynamical mean field theory (DMFT) for inhomogeneous systems, with the non-crossing approximation (NCA) as impurity solver. The domain-size distribution is then obtained from the resulting free energy difference, including volume and domain wall energies. It exhibits non-trivial, non-monotonic behavior. The 1st-order MIT of Mott-Hubbard systems may, hence, be viewed as a percolation problem with self-generated domain disorder. We calculate the electric resistivity ρ(T) by mapping this problem of random nanodomains onto a random resistor network. Within the phase coexistence region, ρ(T) exhibits anomalous linear T depenence.