The Waltz of Atoms: Detecting Circularly Polarized Phonons in Vibrational STEM-EELS

This proposal aims to develop a novel technique for imaging the rotational motion of atoms using Electron Energy Loss Spectroscopy (EELS) in a Scanning Transmission Electron Microscope (STEM).

Such rotational motion of atoms occurs in circularly polarized phonons, which carry angular momentum and play a crucial role in phenomena like inter-valley scattering and the phonon angular momentum Hall effect, with potential applications in technologies such as spintronics, orbitronics, and valleytronics.

Currently, there is no method to probe these phonons locally at the atomic scale.The project will combine theoretical modeling and experimental approaches to demonstrate the feasibility of this detection using phase-shaped electron beams, such as electron vortex beams or aberrated beams.

Theoretical simulations will identify optimal beam shapes and experimental conditions to enhance sensitivity to the rotational motion of atoms.

The experimental component will be conducted based on these findings using a state-of-the-art monochromated STEM at the University of Washington capable of vibrational spectroscopy.Through this proof-of-concept experiment for detecting rotational motion of atoms, this research seeks to contribute to advancing our understanding of the flow of angular momentum in materials and to the development of next-generation quantum devices.