Heat transport and thermoelectric efficiency of two-level quantum dot attached to ferromagnetic electrodes

Energy transport, in the linear response regime, through a two-level quantum dot/molecule attached to ferromagnetic leads is studied in the Coulomb blockade region with use of the Green function formalism. Thermal conductance and figure of merit ZT are calculated and discussed for two configurations of magnetic moments and different polarization factor in the leads. A strong dependence of ZT on polarization is found. A substantial enhancement of efficiency can be observed in molecular junctions with one of energy levels weakly coupled to the leads. Moreover, in systems, in which spin accumulation in electrodes is important, a quite considerable spin efficiency can be expected.