Ian McNulty
The realisation by Allen in 1992 that light can carry quantized orbital angular momentum (OAM) opened a floodgate of new research. Generation, detection and utilization of OAM with electromagnetic waves (from radio to x-rays), matter waves (electrons, neutrons, atoms, and molecules), and even sound have been explored extensively in the years since. The quantum aspects of beams carrying OAM is relevant to processes involving superposition of multiple quantum states and where one or more units of h-bar are exchanged. OAM states now appear to be ubiquitous when wavefunctions are disturbed by discontinuities and more complex topologies in materials. Conversely, possibilities for coupling OAM to quantum materials are of growing fascination, as they could provide a unique handle on both topology and quantum behavior. This talk gives an introduction to research in this area, focusing on x-ray beams carrying OAM and their coupling to material lattice, spin and orbital states. The new generation of high brightness sources is compelling for previously unimaginable OAM experiments with x-rays.