A spin filter with a quantum point contact in a dilute magnetic semiconductor

Within the context of the suggested quantum-mechanical description of hole transport in the ballistic mode, the feasibility of using a quantum point contact as a spin filter in dilute magnetic semiconductors is analyzed. By studying the example of a dilute ferromagnetic GaxMn1−xAs semiconductor, it is established that even smoothing the potential shape does not allow one to attain a 100% spin polarization of the current; in particular, at a constriction width of 3.5 nm, the polarization is 82%. It is shown that the operation region of such a spin filter lies in the narrow range of constriction widths ∼3.5–4.0 nm, and, at large constriction widths, damped oscillations of the spin polarization of the current occur. The spin-orbit splitting in GaxMn1−xAs is sufficient for real operation of a quantum point contact as a spin filter in this material. An increase in the splitting does not produce a substantial increase in the degree of polarization of the incoming current.