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Wednesday, May 13, 2015
3:00 PM - 4:00 PM
MPA-CMMS Conference Room, TA-3, Bldg 32, Rm 134

CMS Colloquium

Investigations of topological states in electron wavefunctions and magnetization

Ben McMorran
University of Oregon, Eugene

We use transmission electron microscopy (TEM) to produce and investigate topological states in coherent free electron wavefunctions, and to image topological spin texture in magnetic materials. Electron vortex beams are composed of helical free electron wavefunctions that carry quantized orbital angular momentum (OAM). To produce such free electron states, we use nanofabricated diffraction gratings to holographically imprint a phase vortex with a prescribed topological charge onto free electron matter waves. We investigate the dynamics and properties of these free electron topological states inside a transmission electron microscope (TEM). We are developing methods to use these beams to probe magnetic features in surfaces and materials. We also use Lorentz microscopy in an aberration-corrected TEM to observe magnetic Skyrmions in FeGd thin films. We are investigating the stability of these features under a range of temperatures and applied magnetic fields, including at room temperature. The capabilities of the Lorentz TEM technique will be discussed.

Host: Marc Janoschek