Enhanced spin figure of merit in a Rashba quantum dot ring connected to ferromagnetic leads

Spin-dependent thermoelectric effect is studied in an Aharonov-Bohm ring with a quantum dot (QD) inserted in one of its arms. We consider that the ring is connected to external ferromagnetic electrodes and there exists Rashba spin-orbit (RSO) interaction in the QD. The spin thermopower S-s and the spin figure of merit Z(s)T are calculated in terms of the Keldysh Green's function method. We found that the Z(s)T value can be significantly enhanced by the coaction of the ferromagnetism of the leads and the RSO interaction. By optimizing the structure parameters, the value of Z(s)T can be up to 1 at room temperature. In addition, pure spin-up (spin-down) thermopower (or Seebeck coefficient) can be generated with high Z(s)T values. Our results indicate that such a single dot ring may be used as a high efficiency spin thermoelectric generator. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4707934]