Thermoelectric effect in a serial two-quantum-dot

We study the thermoelectric effect in a serial-coupled two quantum dots (QDs) device in the Coulomb blockade regime. The electrical conductance, the thermal conductance, the thermopower, and the thermoelectrical figure of merit are calculated by using the Green's function method. It is found that the energy levels of the two dots are split into a series of molecular states, where the electrical and the thermal conductances show resonance peaks. These peaks in the electrical conductance are eliminated by the increase of the temperature, while those in the thermal conductance are enhanced because of the bipolar effect. In quite high temperature regime, the figure of merit has two huge peaks with maximums exceeding 20 in the vicinity of the electron-hole symmetry point. The magnitude of the figure of merit will be suppressed for unequal dots' levels, but is enhanced by the asymmetry of the dot-lead coupling strengths.