Thermoelectric properties of granular metals

We investigate the thermopower and thermoelectric coefficient of nanogranular materials at large tunneling conductance between the grains, ${g}_{T}⪢1$. We show that at intermediate temperatures, $T>{g}_{T}\ensuremath{\delta}$, where $\ensuremath{\delta}$ is the mean energy-level spacing for a single grain, electron-electron interaction leads to an increase in the thermopower with decreasing grain size. We discuss our results in light of the next generation of thermoelectric materials and present the behavior of the figure of merit depending on the system parameters.