Thermopower of double quantum dots: Fano effect and competition between Kondo and antiferromagnetic correlations

The thermoelectric properties of double quantum dot (DQD) systems are investigated and our attention is focused on the interplay between the Fano effect and electronic correlations. If the antiferromagnetic (AF) correlation is weak, the derivative of thermopower with the energy level on dots is positive at the particle-hole symmetric point. With the Fano effect introduced, it becomes negative due to the Fano-Kondo effect. The competition between the Kondo and AF correlations yields a zero in the derivative, and with the direct channel open, in the vicinity of that zero, the derivative undergoes an almost discontinuous hopping with its sign reversed. Away from the particle-hole symmetric point, the variation of thermopower is also related to that interplay. Compared with conductance, thermopower can provide more information on the DQD systems. These results are robust to asymmetry and can be verified in experiments with temperature lower than the Kondo temperature.