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Efficient Fizeau drag from Dirac electrons in monolayer graphene
Wenyu Zhao1, Sihan Zhao1, Hongyuan Li1,2,3
1Department of Physics, University of California, Berkeley, Berkeley, CA, USA.
Nature
|June 24, 2021
Summary
Scientists observed Fizeau drag, a speed modification of light in moving media, in graphene. This plasmonic Doppler effect shows enhanced plasmon polariton speed with electron flow, enabling electrical control.
Area of Science:
- Condensed Matter Physics
- Quantum Optics
- Materials Science
Background:
- Fizeau's 1850 experiment demonstrated light speed modification in moving media.
- Achieving efficient light speed control in fast-moving electron media via electrical current has been challenging.
- The strong coupling between electrons and light suggests Fizeau drag in electron flow systems may manifest as a plasmonic Doppler effect.
Purpose of the Study:
- To experimentally observe Fizeau drag of plasmon polaritons in a fast-drifting electron medium.
- To investigate the plasmonic Doppler effect in monolayer graphene under strong electrical bias.
- To demonstrate electrical control of non-reciprocal surface plasmon polaritons.
Main Methods:
- Utilized strongly biased monolayer graphene with high electron mobility and slow plasmon propagation.
- Employed cryogenic near-field infrared nanoscopy to image plasmon polariton modes.
- Measured Doppler-shifted plasmon wavelengths at low temperatures.
Main Results:
- Directly observed Fizeau drag of plasmon polaritons in graphene.
- Demonstrated non-reciprocal plasmon propagation due to fast-drifting Dirac electrons.
- Measured a plasmon wavelength difference of up to 3.6% between plasmons moving with and against the electron drift.
Conclusions:
- The plasmonic Doppler effect was successfully observed in electronic systems, specifically in biased graphene.
- This work overcomes previous challenges related to fast plasmon speeds in conventional metals.
- Findings offer pathways for electrical control of non-reciprocal surface plasmon polaritons in non-equilibrium systems.
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