Heat current and spin current through a carbon-nanotube-based molecular quantum pump

Abstract

We investigate the heat current and spin current through a carbon-nanotube-based molecular quantum pump. We have derived a general expression for the heat current at finite frequency so that the heat current can be calculated order by order in pumping amplitudes. We have applied our theory to a carbon-nanotube-based quantum pump. The heat current generated during the parametric pumping has been calculated at small frequencies for finite pumping amplitude. At finite frequencies, we have calculated the heat current to the second order in pumping amplitudes. The photon assisted process is clearly observed in the heat current. In the presence of magnetic field, the carbon-nanotube-based quantum pump can function as a spin pump, a molecular device by which a dc pure spin current without accompanying charge current is generated at zero bias voltage via a cyclic deformation of two device parameters. The pure spin current is achieved when the Fermi energy is near the resonant level of the quantum pump. We find that the pure spin current is sensitive to system parameters such as pumping amplitude, external magnetic field, and gate voltage.