Influence of interference effects on thermoelectric properties of double quantum dots

Electron and thermal transport through a double quantum dot/artificial molecule is studied theoretically in the linear response regime with use of Green function formalism. Gradually changing the system geometry from the configuration in series toward parallel ones, we demonstrate interplay between interference processes and thermoelectric effects. If the tunnelling through the antibonding state is progressively reduced, electronic-thermal conductance exhibits features typical for Fano effect with a well-pronounced antiresonance, in which position and intensity depend on the system geometry. Moreover, there is a possibility to manipulate the conductance using an external magnetic field. Thermopower and thermoelectric efficiency, described by the dimensionless figure of merit (FOM) ZT, significantly increase because of interference effects. Interdot Coulomb interaction, described by the parameter U, strongly influences thermoelectric properties. Optimal conditions toward thermoelectricity with high ZT can by fulfilled for relatively strong correlation U. However, dramatic changes can be observed in the region of small U, where efficiency is very low. Because in double dots the interdot electrostatic interaction can be varied in a controlled way, the resonant enhancement of efficiency can be attained.