Exploring neutron Orbital Angular Momentum (OAM) as a future probe of topological materials

It has been known for some time that light can carry orbital angular momentum (OAM) in addition to the more familiar spin angular momentum that is manifested in the polarization of the light wave. Optical OAM expands the arsenal of tools available to explore matter though light-matter interactions. More recently, experiments have demonstrated x-ray OAM and there are indications that beams of quantum particles with non-zero mass (such as neutrons) may also exhibit this phenomenon. We plan to measure neutron scattering from forked diffraction gratings, made using electron-beam lithography by our collaborators at the Center for Nanophase Materials Science at Oak Ridge Lab. Gratings of this type have been shown to produce "vortex light" (i.e. waves with specific values of OAM) when exposed to electromagnetic radiation. Our experiment will be a first step in exploring whether neutron OAM can be added to the neutron scattering toolbox to probe materials and, in particular, to characterize topological structures such as skyrmions that have been proposed for next generation electronic components.