Transport Through Magnetic Quantum Point Contacts

Hybrid magnetic quantum point contacts were fabricated in the plane of a high mobility AlGaAs/GaAs quantum well structure. The hybrid gates are magnetized in an applied in-plane magnetic field and generate both magnetic fringe fields and an electrostatic confining potential. Low-temperature electrical characterization yielded well-resolved conductance plateaus and a strong 0.7-structure in the absence of an applied field. However, the well-known spin polarization effect of a quantum point contact in an applied magnetic field was absent, possibly due to suppressed electron-electron interactions. In addition, a sharply magnetic field dependent washout of the conductance plateaus suggested evidence of a significant effect of the local fringe field on electron transport in the QPC region.