NSLS-II Friday Lunchtime Seminar

Circularly polarized light with spin angular momentum (SAM) is one of the most valuable probes of magnetism. We demonstrate that light beams with orbital angular momentum (OAM), or vortex beams, can also couple to magnetic excitations exhibiting dichroisms in a magnetized medium. In our recent experiments with coherent THz beams we observed that resonant optical absorption in a ferrimagnetic crystal of Dy3Fe5O12 depends strongly on both the handedness of the vortex and direction of the beam propagation with respect to the sample magnetization. This effect exceeds the conventional dichroism for conventional circularly polarized light. Our results demonstrate the potential of the vortex beams with OAM as a new spectroscopic probe of magnetism in matter. A possibility to convert synchrotron radiation at the 22-IR-2 MET beamline into a vortex beam and use it for materials spectroscopy will be also discussed in this talk. In collaboration with T. N. Stanislavchuk1, P. Marsik2, C. Bernhard2, V. Kiryukhin3, S-W. Cheong3, and G. L. Carr4 1 Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 2 Department of Physics, University of Fribourg, Switzerland. 3 Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University 4 NSLS-II, Brookhaven National Lab