Thermoelectric transport through a quantum dot: Effects of asymmetry in Kondo channels

We consider effects of magnetic field on the thermopower and thermoconductance of a single-electron transistor based on a quantum dot strongly coupled to one of the leads by a single-mode quantum point contact. We show appearance of two new energy scales: T(min) similar to vertical bar r vertical bar(2)E(C)(B/B(C))(2) depending on a ratio of magnetic field B and the field BC corresponding to a full polarization of point contact and T(max) similar to vertical bar r vertical bar(2)E(C) depending on a reflection amplitude r and charging energy E(C). We predict that the behavior of thermoelectric coefficients is consistent with the Fermi-liquid theory at temperatures T << T(min) while crossover from non-Fermi-liquid regime associated with a two-channel Kondo effect to Fermi-liquid single-channel Kondo behavior can be seen at T(min) < T < T(max).