Achieving Single-Electron–Single-Photon Interaction in a Transmission Electron Microscope Using 2D Cherenkov Radiation

Yuval Adiv^a, Ido Kaminer^a, Guy Bartal^a, Shai Tsesses^a, Raphael Dahan^a, Kangpeng Wang^a, Yaniv Kurman^a, Hao Hu^b, Xiao Lin^c, Hongsheng Chen^c, Alexey Gorlach^a

^aTechnion - Israel Institute of Technology, Electrical Engineering Department, Haifa, Israel

^bNovitas, Nanoelectronics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore, Singapore

^cInterdisciplinary Center for Quantum Information, State Key Laboratory of Modern Optical Instrumentation, ZJU-Hangzhou Global Science and Technology Innovation Center

Proceedings of Electron Beam Spectroscopy for Nanooptics 2021 (EBSN2021)

Online, Spain, 2021 June 14th - 15th

Organizers: Mathieu Kociak and Nahid Talebi

Poster, Yuval Adiv, 031
Publication date: 8th June 2021

ePoster:

Over 80 years of research into free-electron radiation have not yet changed its popular description as a three-dimensional, classical electromagnetic wave^1–5, best exemplified by the Cherenkov effect – the radiation of charged particles exceeding the speed of light in a medium^1,6. Free-electron radiation was predicted to fundamentally change in reduced dimensionality^7–9 and to exhibit novel phenomena due to the quantized nature of the electromagnetic field^10–12. However, neither has been demonstrated experimentally.

Here, we present the first observation of the two-dimensional Cherenkov effect, wherein free electrons emit narrow-bandwidth surface polaritons and shift their energy following the Cherenkov condition. The dimensionality and bandwidth of the effect enable a quantum coupling strength over two orders of magnitude larger than in previous experiments^13–20, leading to a single-electron–single-polariton interaction. This observation brings us to the regime of ultrastrong coupling between a free electron and a polariton, which is manifested by several quantized emission events in the electron energy loss spectrum (EELS).

To reach the regime of single-electron–single-photon interaction, we combined a dispersion-engineered structure^21,22 supporting surface polariton modes, with the high electron beam quality of a transmission electron microscope. Our results show the first example of electromagnetic field quantization in a coherent cathodoluminescence process, where the EELS measurement is directly correlated to emission of a polariton Fock state.

As a future outlook our findings pave the way to discovering previously-unexplored phenomena in free-electron quantum optics^12,23, facilitating the use of free electrons for quantum information applications^24,25 and as bright quantum emitters for heralded single- and multi-photon states^26–29.

References:

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[21] Mechel, C. et al. Quantum correlations in electron microscopy. Optica 8, 70–78 (2021).

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[25] Talebi, N. A directional, ultrafast and integrated few-photon source utilizing the interaction of electron beams and plasmonic nanoantennas. New J. Phys. (2014).

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