  Magnetic focussing of charge carriers in two-dimensional systems provides a
solid state version of a mass spectrometer. In the presence of a spin-orbit
interaction, the first focussing peak splits into two spin dependent peaks,
allowing focussing to be used to measure spin polarisation and the strength of
the spin-orbit interaction. In hole systems, the k^3 dependence of the Rashba
spin-orbit term allows the spatial separation of spins to be changed in-situ
using a voltage applied to an overall top gate. Here we demonstrate that this
can be used to control the splitting of the magnetic focussing peaks.
Additionally, we compare the focussing peak splitting to that predicted by
Shubnikov-de Haas oscillations and k.p bandstructure calculations. We find that
the focussing peak splitting is consistently larger than expected, suggesting
further work is needed on understanding spin dependent magnetic focussing.

Mesoscale and Nanoscale Physics