Photon-Selective Spin-Dependent Transport Through a Quantum Dot Driven by Electrical and Thermal Biases

Abstract

Impacts of both the electrical and thermal biases on the spin-dependent transport through a quantum dot are studied by using the nonequilibrium Green’s function technique. Due to the Zeeman splitting of the dot level, the spin polarization of the current approaches to ± 1 at some photon-induced transport channels when the spin-split dot levels locate in between the conduction window opened by the electrical bias. While under zero electrical bias but finite thermal bias, a totally 100% spin-polarized current emerges at some photon frequencies, where spin-up and spin-down electrons are selected with the help of the photon field. Moreover, for several photon frequencies, the currents of different spin components may tunnel through the dot in opposite directions, resulting in a pure spin current. We find that in both cases the intensity and the position of the resonant peaks of the spin-polarized currents are sensitive to the intradot Coulomb interaction. When the two biases coexist in the system, the intensity and the spin-polarization of the currents can be effectively adjusted by changing their relative strengthes.