  In the present work, we investigate the thermoelectric properties of a
T-shaped double quantum dot system coupled to two metallic leads incorporating
the intra-dot Coulomb interaction. We explore the role of the interference
effects and Coulomb blockade on the thermoelectric efficiency of the system in
the linear and nonlinear regimes. We studied as well the effect of a Van-Hove
singularity of the leads density of states (DOS) at the neighborhood of the
Fermi energy, a situation that can be obtained using a carbon nanotube, a
graphene nano-ribbon or other contacts with one-dimensional properties. The
system is studied above the Kondo temperature. The Coulomb blockade of the
electronic charges is studied using the Hubbard III approximation, which
properly describes the transport properties of this regime. In the linear
response, our results show an enhancement of the thermopower and the figure of
merit of the system. For a nonlinear situation, we calculate the thermoelectric
efficiency and power output, concluding that the T-shaped double quantum dot is
an efficient thermoelectric device. Moreover, we demonstrate the great
importance of the DOS Van-Hove singularity at the neighborhood of the Fermi
energy to obtain a very significant increase of the thermoelectric efficiency
of the system.
