Filtering Spin with Tunnel-Coupled Hole Quantum Wires

Creating spin-polarized currents in nonmagnetic semiconductors is one of the key prerequisites for realizing spintronics devices. We have shown previously that the k-linear Rashba spin splitting present in two-dimensional (2D) electron systems can be utilized in a momentum-selective tunneling geometry to design a spin filter without using magnetic fields or ferromagnetic contacts. Motivated by the fact that spin–orbit effects are typically much stronger in 2D hole systems, we consider quantum wires formed by additional confinement of the lowest (heavy-hole) 2D valence subband. Its k ³-type Rashba term gives rise to a k-linear spin splitting for holes in the quantum wire. Implementation of the spin-filter design is then analogous to the electron case but, in the hole system, requires less momentum selectivity and should therefore be easier to realize.