Spin-polarized transport in Rashba quantum point contacts

Two types of quantum point contacts (QPCs), side-gate quantum wire and split-gate QPCs, were fabricated at high In-content InGaAs/InAlAs single heterojunction which confines two-dimensional electron gas revealing strong Rashba spin–orbit interaction. In the side-gate quantum wire QPC, the conductance quantization in unit of 0.5(2e2/h) was mostly observed in the various samples with different dimensions. This is in contrast to the result in the split-gate QPC, where we confirmed usual (2e2/h) conductance quantization. Since those results were observed under zero magnetic field, the 0.5(2e2/h) quantization could be attributed not to the spin splitting but to the possible spin polarized transport due to the mode coupling between the one-dimensional subbands expected in sufficiently narrow adiabatic constrictions.