Thermospin effects in a quantum dot connected to normal leads

• The thermospin effects in a quantum dot connected to normal leads have been investigated.
• We obtain a tunable pure spin current and highly spin-polarized current.
• A pure spin Seebeck coefficient is found.
• The spin and charge current can be controlled by the amplitude of microwave fields.
• We can modulate both amplitude and direction of the spin current by the phase of microwave fields.

We study thermospin effects through a quantum dot (QD) with a magnetic field attached to normal leads. In the stationary case, we obtain a tunable pure spin current and highly spin-polarized current. The spin Seebeck coefficient can be as large as the charge counterpart and a pure spin Seebeck coefficient is found. In the presence of microwave (MW) fields, the spin and charge current can be controlled by the amplitude of MW fields. Due to the photon-assisted tunneling, the behavior of current spin polarization SP becomes complicated and we can find a large SP   in a larger range of the QD level VgVg. At zero VgVg, we can modulate both amplitude and direction of the spin current by the phase ϕ of MW fields. More peaks and valleys appear in the Seebeck coefficient owing to more sub-channels opened by the photons. Like the current, the spin Seebeck coefficient can be also tuned by ϕ.