We study the thermoelectric transport through a double-quantum-dot system with spin-dependent interdot cou- pling and ferromagnetic electrodes by means of the non-equilibrium Green＇s function in the linear response regime. It is found that the thermoelectric coefficients are strongly dependent on the splitting of the interdot coupling, the relative magnetic configurations, and the spin polarization of leads. In particular, the thermoelectric efficiency can reach a considerable value in the parallel configuration when the effective interdot coupling and the tunnel coupling between the quantum dots and the leads for the spin-down electrons are small. Moreover, the thermoelectric efficiency increases with the intradot Coulomb interaction increasing and can reach very high values at appropriate temperatures. In the presence of the magnetic field, the spin accumulation in the leads strongly suppresses the thermoelectric efficiency, and a pure spin thermopower can be obtained.
We investigate the strongly interacting lattice Bose gases on a lattice with two-body interaction of nearest neighbors characterized by pair tunneling. The excitation spectrum and the depletion of the condensate of lattice Bose gases are investigated using the Bogoliubov transformation method and the results show that there is a pair condensate as well as a single particle condensate. The various possible quantum phases, such as the Mott-insulator phase （MI）, the superfluid phase （SF） of an individual atom, the charge density wave phase （CDW）, the supersolid phase （SS）, the pair-superfluid （PSF） phase, and the pair-supersolid phase （PSS） are discussed in different parametric regions within our extended Bose-Hubbard model using perturbation theory.
We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction （RSOI）, coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two ferromagnetic leads and two quantum dots form a ring threaded by Aharonov-Bohm （AB） flux. This device possesses normal quasiparticle transmission between the two ferromagnetic leads, and normal and crossed Andreev reflections providing conductive holes. For the appropriate spin polarization of the ferromagnetic leads, RSOI and AB flux, the pure spin-up （or spin-down） current without net charge current in the right lead, which is due to the equal numbers of electrons and holes with the same spin-polarization moving along the same direction, can be obtained by adjusting the gate voltage, which may be used in practice as a pure spin-current injector.
