Thermal spin current through a double quantum dot molecular junction in the Coulomb blockade regime

Based on non-equilibrium Green's function methods, we investigate the thermal spin current through a double quantum dot (DQD) molecular junction in the Coulomb blockade regime. An external magnetic field and a temperature difference are utilized to manipulate the electron spin degree of freedom in the DQD device. When the chemical potentials are aligned with the electron-hole symmetry point, a very steady pure-spin-current thermal generator is achieved. This is because the transmission nodes of different spin channels relative to chemical potentials have a perfect mirror symmetry configuration. In addition, the pure spin current also appears near resonant regions induced by the molecular states. Particularly interesting is that the sign of the pure spin current in the electron-hole symmetry point is opposite to those appearing near resonant regions in the strong Coulomb interaction regime.