Short Introduction of a Vortex Beam of Electrons

In the present textbook, a plane wave and a wave packet formed from the plane waves are used for explanation of electron microscopy and diffraction. How about other solutions of Schrodinger’s equation for a free electron? This is a start of understanding of a vortex beamVortex beam of electrons studied since the beginning of the twenty-first century. We have to know about a beam propagating with rotational symmetry along z-direction (optical axis).