Effects of Degenerated Energy Levels on the Thermoelectric Properties of Quantum Dot Junction System

Project Details

Description

Recently, many efforts have been devoted to the search of high-efficiency thermoelectric (TE)materials, because of the high demand of energy-saving solid state coolers and powergenerators. TE devices have very good potential for green energy applications due to theirdesirable features, including low air pollution, low noise, and long operation time. However,currently there exists certain barrier for TE devices to replace conventional refrigerators andpower generators since TE materials with figure of merit (ZT) larger than three are not yetreported. Theoretical studies have indicated that the TE behaviors of a molecular quantum dot(QD) can reach Carnot efficiency in the absence of phonon heat flow. Such a divergence ofZT for QDs is related to the violation of the Wiedeman-Franz law. Because it is verychallenge to fully blockade acoustic phonon heat flow in the implementation of solid state TEdevices. Finding a way to enhance ZT of QD junctions in the presence of a finite phononthermal conductivity is crucial.This project will discuss the effects of degenerated energy levels (DELs) on thethermoelectric properties of QD junction systems. First year, we plane to investigate howDELs to influence the ZT value of junction system (linear response regime). The second year,how DELs to influence the efficiency of heat engine driven by a large temperature bias. Weillustrate the electron coherent tunneling effects on the ZT values of QD molecules withDELs in the third year. When we investigate the effects of degenerated energy levels onthermoelectric properties of QD junctions, electron Coulomb interactions play a significantrole for electron transport behaviors. For high DELs, for example L=4 (not includingelectron spin), we have to take into account Green’s functions and all correlation functionsup to 8 particles if there are just one energy level for each QD. Compared with thecalculation of ZT optimization in the first year, we will have heavily numerical calculationsfor studying heat engine operated at nonlinear response regime (a large temperature bias).Therefore, we are going to complete this calculation in the second year. Electron coherenttunneling effects can not be ignored when we involve TE properties of quantum dotmolecules with DELs. The interplay between electron-electron interactions and electroncoherent tunneling processes make the behavior of electron transport very complicate. Wediscuss this combination effects on the design of solid state cooler in the third year.
StatusFinished
Effective start/end date1/08/1731/07/18

UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):

  • SDG 6 - Clean Water and Sanitation
  • SDG 11 - Sustainable Cities and Communities
  • SDG 17 - Partnerships for the Goals

Keywords

  • thermoelectric effects
  • figure of merit
  • heat engine
  • nanostructure
  • quantum dots
  • Electron Coulomb interactions
  • electron coherent tunneling
  • Green’s functions

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