Spin-dependent thermoelectric figure of merit in a quantum dot

We theoretically investigate the spin-dependent thermoelectric effects in a quantum dot that is connected with a normal metal lead and a ferromagnetic metal lead, by using the nonequilibrium Green's function method. The thermoelectric figure of merit ZT can be evaluated in several different ways, for example, by imposing a condition that the spin accumulation across the system is zero (Delta mu(s) = 0) or that the spin current is zero (I-s = 0). We find that ZT in the case of Delta mu(s) = 0 is always greater, especially when the spin polarization degree of the ferromagnetic lead is large. Meanwhile, in each case the ZT value drops when the spin polarization degree is increased. Effects of electron interaction on thermoelectric properties are also discussed briefly. (C) 2015 Elsevier B.V. All rights reserved.