Nonmonotonic 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 nonmonotonic 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.

Figure 1

(Color online) (a) Thermopower in the high-temperature limit, $Q_1$ and $Q_2$, vs. electron density, $n$. (b) Temperature dependence of the thermopower calculated by DMFT with the NCA impurity solver, for various parameter sets of $U$ and $n$.

Figure 2

(Color online) Temperature dependence of the thermopower for $n=1.2$ calculated by DMFT with the IPT impurity solver. Dashed and dotted lines are $Q_1$ and $Q_2$ for $n=1.2$, respectively.

Figure 3

Magnetic field dependence of the thermopower for $k_{B}T=0.02$ and $n=1.2$ calculated by DMFT with the IPT impurity solver.

Figure 4

(Color online) The density of states (DOS) for $n=1.2$ at $k_{B}T=0.02$. Thick line is the result of DMFT with the IPT impurity solver for $U=1.5,B=0$. For reference, DOS for $U=0,B=0$ is presented by a thin line.