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Electron Recoil via Sample Momentum Transfer in Optical-Mode Excitation
Akira Yasuhara1, Yamato Kirii2, Takumi Sannomiya2
1JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo, 196-8558, Japan.
Physical Review Letters
|June 22, 2026
Summary
Free electrons transfer momentum to planar samples during optical mode excitation, altering their properties. This momentum exchange, previously overlooked, is significant when samples are tilted, with potential for opposite momentum transfer.
Area of Science:
- Quantum optics
- Nanoscale light-matter interactions
- Electron spectroscopy
Background:
- The interaction between free electrons and optical modes is crucial for quantum and nanoscale phenomena.
- Momentum exchange during these interactions has been largely overlooked.
- Understanding this momentum transfer is key to controlling light-matter interactions at the nanoscale.
Purpose of the Study:
- To experimentally demonstrate and characterize momentum transfer from free electrons to planar samples during optical mode excitation.
- To investigate the influence of this momentum transfer on the sample's properties, such as its dispersion relation.
- To explore conditions under which momentum transfer occurs, including its direction.
Main Methods:
- Utilizing momentum-resolved electron energy-loss spectroscopy (M-EELS).
- Experimentally probing free electron-sample interactions during optical mode excitation.
- Analyzing the modification of the apparent dispersion relation of planar samples.
Main Results:
- Direct experimental evidence of momentum transfer from free electrons to planar samples was obtained.
- The momentum transfer was shown to modify the apparent dispersion relation, especially when the sample was tilted.
- Under specific experimental conditions, the sample was observed to receive momentum in the direction opposite to the incident electron beam.
Conclusions:
- Momentum transfer between free electrons and optical modes in planar samples is a significant, experimentally verifiable phenomenon.
- This momentum exchange impacts the sample's optical properties and can be controlled by sample orientation.
- The findings open new avenues for manipulating light-matter interactions at the nanoscale through electron-sample momentum transfer.
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