Spin filtering and spin accumulation in an electron stub waveguide with spin-orbit interaction

We investigate spin-dependent transport properties of a two-terminal electron waveguide, attached with a side arm, with Rashba spin-orbit interaction (SOI). The interference between the bound states in the side arm and the continuous states in the straight channel gives rise to broad valleys in the conductance spectrum. At these Fano antiresonances, a large transverse spin polarization can be created by the SOI-induced effective magnetic field. The magnitude of the spin polarization in this waveguide structure can be electrically tuned by variation of the stub length or the SOI strength, suggesting that the SOI-modulated stub waveguide structure can be used as an electrically tunable spin filter. It is also found that highly polarized spin-density islands can form inside the stub. Thus the stub waveguide structure could also be utilized to create local magnetic moments and for information storage.