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

Abstract

The quantum interference and orbital filling effects on the thermoelectric (TE) properties of quantum dot (QD) molecules with high figure of merit are illustrated via the full solution to the Hubbard-Anderson model in the Coulomb blockade regime. It is found that under certain conditions in the triangular QD molecule (TQDM), destructive quantum interference (QI) can occur, which leads to vanishingly small electrical conductance, while the Seebeck coefficient is modified dramatically. When the TQDM is in the charge localization state due to QI, the Seebeck coefficient is seriously suppressed at low temperature, but is highly enhanced at high temperature. Meanwhile, the behavior of the Lorenz number reveals that it is easier to block charge transport via destructive QI than the electron heat transport at high temperatures. The maximum power factor (PF) in the TQDM occurs under full-filling conditions. Nevertheless, low-filling conditions are preferred for getting the maximum PF in serially coupled triple QDs in general. In double QDs, the maximum PF can be achieved either with orbital-depletion or orbital-filling as a result of electron-hole symmetry. Our theoretical work provides a useful guideline for the advancement of the nanoscale TE technology.

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

“…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. 5 in which we reveal why electron Coulomb interactions can be neglected in this study of N = 25.…”

A heat engine made of quantum dot molecules with high figure of merits

“…Noting that the interdot Coulomb interactions as well as intradot Coulomb interactions play a significant role on the charge transport in semiconductor QD arrays or molecular chains. [10][11][12][13] Because we are interested in the case that the thermal energy is much smaller than intradot Coulomb interactions, we consider QDs with only one energy level per dot.…”

“…( 3) and ( 4) by considering all correlation functions and Green's functions. [12,13] To design an EHE driven by an applied temperature-bias, the thermal induced voltage (eV th = µ L − µ R ) across the external load with conductance G ext needs to be calculated for a given temperature bias ∆T . To obtain eV th , we have to solve self-consistently all correlation functions appearing in Eq.…”

“…Most theoretical studies of TE properties are limited in the linear response regime. [10][11][12][13] The many-body effect of QDMs also presents a big challenge to the development of theoretical studies for TE properties. In this article, we study the nonlinear behavior of EHE made of serially coupled triple QDs (SCTQDs) based on a previously developed numerically method, [12,13] which can suitably address the many body effect in the Coulomb blockade regime.…”

“…[10][11][12][13] The many-body effect of QDMs also presents a big challenge to the development of theoretical studies for TE properties. In this article, we study the nonlinear behavior of EHE made of serially coupled triple QDs (SCTQDs) based on a previously developed numerically method, [12,13] which can suitably address the many body effect in the Coulomb blockade regime. In addition, we investigate an engine with directiondependent electrical output driven by a temperature-bias for application as a novel nonlinear TE devices.…”