Impurity effects on the spin-polarized transport through armchair carbon nanotubes contacted by ferromagnetic leads are investigated theoretically. The length of the nanotube can cause on-resonance and off-resonance behaviors of the spin-coherent transport. The impurity suppresses the...

The supercurrent through an Aharonov-Bohm interferometer containing two parallel quantum dots connected with two superconductor leads is investigated theoretically. The possibility of controlling the supercurrent is explored by tuning the quantum dot energy levels and the total magnetic flux. By...