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.

Thermoelectric energy harvesting with quantum dots

“…[19]. Two-terminal geometries using mesoscopic conductors have been considered, notably using quantum dots [5,20,21,7,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43]. In the two-terminal geometry, both temperature and voltage bias are applied to the sample and the thermoelectric response is investigated.…”

Quantum interference and structure-dependent orbital-filling effects on the thermoelectric properties of quantum dot molecules

“…t ℓ,j describes the electron interdot hopping. Noting that the interdot Coulomb interactions as well as intradot Coulomb interactions play a significant role on the charge transport for semiconductor QDs [9] and molecular structures. [22][23][24] Using the Keldysh-Green's function technique, [26,27] the charge and heat currents from reservoir α to the QDM junction are calculated according to the Meir-Wingreen formula…”

“…[8] In the Coulomb blockade regime, electron transport process is seriously suppressed by the electron Coulomb interactions, causing κ e and G e to be reduced simultaneously. [9] On the other hand, under the condition κ e /κ ph ≪ 1, one can increase the power factor (PF) [10][11][12][13][14][15] and decrease the phonon thermal conductance [16][17][18][19][20][21] simultaneously to optimize ZT . The ZT enhancement of QDSL mostly arises from changes induced by dimensional confinement in the electronic band structures as well as en-hanced phonon scattering resulting from the scattering at nanowire surface and interfaces surrounding QDs.…”

Heat diodes made of quantum dots embedded in nanowires connected to metallic electrodes

“…The expression of T LR (ǫ) for N=25 in terms of a single particle retarded Green's functions can be found in our previous work. 30) It is a prohibited challenge to include all correlation functions arising from electron Coulomb interactions for N = 25. 31,32) The affect of electron Coulomb interactions on the electron transport of double QDs is clarified in Fig.…”