The thermoelectric transport properties in strongly correlated single quantum dot with splitting spin

We study properties of thermocurrent through a single quantum dot (QD) system, which has an energy difference between levels of the spin-up and the spin-down as well as a Coulomb interaction between them under the temperature settings both with and without the Kondo effect. Two additional sign-changings of the thermocurrent with changing the energy level of QD is observed. Due to the Coulomb interaction between the electrons with different spins, only changing the energy level of one spin will cause significant variations for the thermocurrent of the two spins. Depending on the temperature, namely, whether the Kondo effect takes place, the Coulomb interaction exhibits different influences on thermocurrent. At high temperatures, the thermocurrent simply changes from positive to negative as the energy level of one spin increases. The lower temperatures trigger the Kondo effect and make the influence of the Coulomb interaction stand out. In this case, the thermocurrent undergoes extra multiple sign-changings and it can be explained by the changing of the electron states and hole states within the temperature bias window. Meanwhile, the splitting of energy levels leads to an obvious spin-polarized thermocurrent in the system. The spin-polarized thermocurrent changes from positive to negative as the energy level of one spin increases and the changing behavior depends on the temperature. In addition, the Coulomb interaction between two spins also profoundly affects the sign-changing phenomenon of thermocurrent at low temperatures.