Thermoelectric properties of a quantum dot array connected to metallic electrodes.

ABSTRACT

The thermoelectric properties of a quantum dot array (QDA) embedded in a nanowire connected to metallic electrodes are investigated theoretically via the extended Hubbard model in the Coulomb blockade regime. Coupled quantum dots (QDs) with dot number N = 2-5 are considered. It is found that the thermoelectric properties converge to almost the same results when N approaches 5, indicating that our results are applicable for a QDA with a large number of QDs. Our studies indicate that in order to achieve the optimal figure of merit (ZT), it is preferable to have the QD energy levels above the Fermi energy (EF) of the electrodes of the QDA junction. The effects of QD energy level and interdot coupling variations (due to the QD size and position fluctuation) on the thermoelectric properties are also examined. We find that the QD size fluctuation significantly suppresses the maximum ZT in the weak interdot hopping strength (tℓ,j). We also find that the Seebeck coefficient is insensitive to tℓ,j and the tunneling rates when the QD energy levels are far above EF. For a given tℓ,j and large on-site Coulomb interactions, increasing the QD number N in the QDA would suppress the maximum ZT value. It is possible to achieve an optimal ZT larger than 3 by tailoring the physical parameters of the QDA junction system.