Field-orientation dependence of the Zeeman spin splitting in (In,Ga)As quantum point contacts

We study the Zeeman spin splitting in a quantum point contact (QPC) etched into an InGaAs/InP heterostructure for three orthogonal magnetic field orientations with respect to the QPC. For the two in-plane orientations we observe an isotropic Zeeman spin splitting, which becomes stronger as the system is made more one dimensional. The Lande g factor is enhanced by up to a factor of two compared to two-dimensional electron systems in InGaAs/InP. A much larger Zeeman splitting is observed when the field is oriented perpendicular to the heterostructure, resulting in a g factor of 15.7 in the one-dimensional limit.