Electron-beam formation from spin-orbit interactions in zinc-blende semiconductor quantum wells.

We find a dramatic enhancement of electron propagation along a narrow range of real-space angles from an isotropic source in a two-dimensional quantum well made from a zinc-blende semiconductor. This "electron-beam" formation is caused by the interplay between spin-orbit interaction originating from a perpendicular electric field to the quantum well and the intrinsic spin-orbit field of the zinc-blende crystal lattice in a quantum well, in situations where the two fields are different in strength but of the same order of magnitude. Beam formation is associated with caustics and can be described semiclassically using a stationary phase analysis.