1109.3066 (Tomaz Rejec et al.)

Spin-thermopower in interacting quantum dots    [PDF]

Tomaz Rejec, Rok Zitko, Jernej Mravlje, Anton Ramsak

Using analytical arguments and the numerical renormalization group method we
investigate the spin-thermopower of a quantum dot in a magnetic field. In the
particle-hole symmetric situation the temperature difference applied across the
dot drives a pure spin current without accompanying charge current. For
temperatures and fields at or above the Kondo temperature, but of the same
order of magnitude, the spin-Seebeck coefficient is large, of the order of
k_B/e. Via a mapping, we relate the spin-Seebeck coefficient to the
charge-Seebeck coefficient of a negative-U quantum dot where the corresponding
result was recently reported by Andergassen et al. in Phys. Rev. B 84, 241107
(2011). For several regimes we provide simplified analytical expressions. In
the Kondo regime, the dependence of the spin-Seebeck coefficient on the
temperature and the magnetic field is explained in terms of the shift of the
Kondo resonance due to the field and its broadening with the temperature and
the field. We also consider the influence of breaking the particle-hole
symmetry and show that a pure spin current can still be realized provided a
suitable electric voltage is applied across the dot. Then, except for large
asymmetries, the behavior of the spin-Seebeck coefficient remains similar to
that found in the particle-hole symmetric point.

View original: http://arxiv.org/abs/1109.3066