Breathing mode of relativistic twisted electron beams under periodic magnetic field

Abstract

Transmission electron microscopy typically works with relativistic electron beams of energy 200–300 keV whose wavelength is on the picometer scale. Here, we study theoretically the relativistic dynamics of twisted Dirac-electron beams driven by a time-oscillating magnetic field. The spatial density distribution and the spinor wave-functions of twisted electron beams at each instant time t are obtained. It is demonstrated that the spatial density distribution of electrons can be changed periodically by the external field, whose change is very similar to the “Breathing”. Correspondingly, the azimuthal component of the current changes periodically with the magnetic field. The central “spot size” of spatial distribution of is directly related to the magnitude of the magnetic field. Our results suggest that twisted electron beams are promising for testing the magnitude and frequency of ac magnetic fields created by microsources.