Spin filtering in four-terminal wire networks with spin-orbit coupling

We propose that spin filtering devices could be based on 4-terminal networks made of quantum wires with Rashba spin-orbit coupling, in the absence of magnetic field. For unpolarized injected electrons in the two input terminals spin polarization is obtained in the two output terminals for the finite network geometries: (i) two-bar ladder (ii) ice-tray lattice (iii) mixture of ladder and ice-tray lattice, and (iv) square lattice of finite width. The obtained spin polarizations oscillate by varying the length of the network and for case (iv) larger values are found, closer to 100%, with the maximum increasing with the increase of lattice width. We also obtain a nearly binary spin conductance output by adjusting the bias voltages in input leads. The physical origin of spin filtering based on quantum interference in such networks and the prospects for creating effective spin filter devices is discussed