Theory of the energy-spectrum dependence of the electronic thermoelectric tunneling coefficients of a quantum dot

The effect of the energy spectrum of a quantum dot on the electron conductance, thermopower, and thermal conductance when the dot is weakly coupled to two electron reservoirs is investigated within the sequential tunneling regime. The cases of nonequidistant and/or of degenerate energy levels spectrum are considered. Analytical formalism for the transport coefficients is derived that provides interpretation of the physical behavior of the system in the quantum regime where the discreteness of the energy spectrum of the quantum dot plays a major role in transport properties. The derived formalism refers to a general case of energy spectrum, and it can be therefore applied to real cases such as nanocrystals and molecules. It is found that the details of the energy spectrum more drastically affect the magnitude of the electron thermal conductance at low temperatures. Depending on the charging state of the quantum dot, the thermoelectric efficiency could be tuned.