Friday 25 Febuary; Leiden, Jo Verbeek "Electrons with a twist: vortex electron beams in the electron microscope"



Joan van der Waals Colloquium
Location: De Sitterzaal/ Oortgebouw

Time: 16:00 - 17:00 hrs

AbstractElectron microscopists are used to work with the concept of spherical and plane waves to describe the wave function of the accelerated electrons in the microscope column. In this talk I will demonstrate that also electron waves with helical wavefronts are possible. Such waves are labelled with a so-called topological charge and carry angular momentum. Their counterpart in optics was only discovered in the nineties while first demonstrations of electron vortex waves only appeared in 2010. Experimental realisation of such electron vortex waves will be demonstrated as well as first applications in electron energy loss spectroscopy. The helicity of the vortex beam breaks time reversal symmetry and changes the selection rules that are present in EELS experiments. As a consequence, magnetic information of atoms in a sample becomes available. The potential to combine this newly obtained magnetic information with
atomic resolution is discussed as well as other potential applications