Spin - orbit pendulum: the microscopic Stern - Gerlach effect

Abstract

We are studying the propagation of a wavepacket in a spherical harmonic potential to which is added a spin - orbit potential. The conditions are such that the wavepacket would be coherent and centred on a circular orbit in the absence of spin - orbit coupling. This additional term splits the wavepacket into two components which are approximately coherent states and which move in an opposite sense. The interference of these wavepackets produces the phenomenon of collapse and revival well known in the Jaynes - Cummings model; it can also be interpreted as a microscopic Stern - Gerlach effect. The spin density exhibits an interesting continuous evolution in time. The oscillations of a fraction of average angular momentum between the spin and ordinary subspaces justify the name of spin - orbit pendulum.