Zeeman splitting and subband spacing in ballistic Ga$_{0.25}$In$_{0.75}$As/InP quantum point contacts

Spin-resolved transport in low-dimensional, solid state systems is a leading area of research at the nanoscale, due to potential device applications that combine quantization with the spin degree of freedom. The realization of such devices requires both a well-resolved energy level spectrum and a large splitting of the spin-degeneracy. Here we investigate the transport properties of a ballistic quantum point contact (QPC) etched into a high indium content strained GaInAs/InP heterostructure, a system with strong spin-orbit coupling and large 1D subband spacings. We have measured the 1D subband spacing using two independent methods, and find it to be $\sim $10 meV, with a very steep confining potential. We also present data studying the Zeeman splitting of the 1D subbands for different magnetic field orientations.