Non-monotonic temperature dependence of thermopower in strongly correlated electron systems

We examine the temperature dependence of thermopower in the single band Hubbard model using dynamical mean-field theory. The strong Coulomb interaction brings about the coherent-to-incoherent crossover as temperature increases. As a result, the thermopower exhibits non-monotonic temperature dependence and asymptotically approaches values given by the Mott-Heikes formula. In the light of our theoretical result, we discuss the thermopower in some transition metal oxides. The magnetic field dependence of the thermopower is also discussed.Comment: 4 pages, 4 figure

Photo-induced insulator-metal transition of a spin-electron coupled system

The photo-induced metal-insulator transition is studied by the numerical simulation of real-time quantum dynamics of a double-exchange model. The spatial and temporal evolutions of the system during the transition have been revealed including (i) the threshold behavior with respect to the intensity and energy of light, (ii) multiplication of particle-hole (p-h) pairs by a p-h pair of high energy, and (iii) the space-time pattern formation such as (a) the stripe controlled by the polarization of light, (b) coexistence of metallic and insulating domains, and (c) dynamical spontaneous symmetry-breaking associated with the spin spiral formation imposed by the conservation of total spin for small energy-dissipation rates

Temperature Dependence of Thermopower in Strongly Correlated Multiorbital Systems

Temperature dependence of thermopower in the multiorbital Hubbard model is studied by using the dynamical mean-field theory with the non-crossing approximation impurity solver. It is found that the Coulomb interaction, the Hund coupling, and the crystal filed splitting bring about non-monotonic temperature dependence of the thermopower, including its sign reversal. The implication of our theoretical results to some materials is discussed.Comment: 3 pages, 3 figure

Low energy electronic states and triplet pairing in layered cobaltates

The structure of the low-energy electronic states in layered cobaltates is considered starting from the Mott insulating limit. We argue that the coherent part of the wave-functions and the Fermi-surface topology at low doping are strongly influenced by spin-orbit coupling of the correlated electrons on the $t_{2g}$ level. An effective t-J model based on mixed spin-orbital states is radically different from that for the cuprates, and supports unconventional, pseudospin-triplet pairing.Comment: 4 pages, 3 figure

Structure-related transport properties of A-site ordered perovskite Sr3ErMn4-xGaxO10.5-d

We report x-ray diffraction, resistivity, thermopower, and magnetization of Sr3ErMn4-xGaxO10.5-d, in which A-site ordered tetragonal phase appears above x=1, and reveal that the system exhibits typical properties seen in the antiferromagnetic insulator with Mn3+. We succeed in preparing both A-site ordered and disordered phases for x=1 in different preparation conditions, and observe a significant decrease of the resistivity in the disordered phase. We discuss possible origins of the decrease focusing on the dimensionality and the disordered effect.Comment: 4 pages, 6 figure