Chiral phonons possessing valley pseudo angular momentum (PAM) underlie a diversity of quantum phenomena of fundamental and applied importance, but are challenging to probe directly. We show that deficiencies of typical momentum-resolved electron energy loss measurements that make it impossible to distinguish the PAM of chiral phonons can be overcome by introducing pinwheel free electron states with well-defined PAM. Transitions between such states generate 2D periodic arrays of in-plane field vortices with polarization textures tailored to selectively couple to desired chiral mode symmetries.
@article{arxiv.2405.01826,
title = {Strategy for Direct Detection of Chiral Phonons with Phase-Structured Free Electrons},
author = {Marc R. Bourgeois and Andrew W. Rossi and David J. Masiello},
journal= {arXiv preprint arXiv:2405.01826},
year = {2024}
}