Angular dynamics of small nanoparticles induced by non-vortex electron beams

Area of Science:

• Theoretical physics
• Nanotechnology
• Classical electrodynamics

Background:

• Electron beams can transfer momentum to nanoparticles.
• Understanding angular dynamics is crucial for nanoscale manipulation.

Purpose of the Study:

• Investigate angular dynamics of small nanoparticles induced by fast non-vortex electron beams.
• Obtain general expressions for torque and angular momentum transfer.
• Analyze the nature and directionality of transferred angular momentum.

Main Methods:

• Full-retarded classical electrodynamics approach.
• Small particle limit approximation.
• Analytical and numerical calculations for spherical nanoparticles.

Main Results:

• Derived general expressions for torque and angular momentum transfer.
• Angular momentum transfer is electric in nature and depends on electron trajectory.
• Transfer is two orders of magnitude smaller than with vortex beams for Al and Au nanoparticles.
• A 5nm gold nanoparticle can spin up to 29.3 Hz.

Conclusions:

• Non-vortex electron beams transfer electric angular momentum to nanoparticles.
• This transfer mechanism is less efficient than with vortex beams.
• Potential for controlled nanoscale spinning applications exists.