Physicists ‘trick’ photons behaving like electrons using a ‘synthetic’ magnetic field


Filtering a honeycomb metasurface produces an artificial magnetic field for light that can be tuned by embedding the metasurface inside a cavity waveguide. Sincerely: University of Exeter

Scientists have discovered an elegant way of manipulating light using a ‘synthetic’ Lorentz force – which is responsible for many fascinating phenomena including aurora borealis in nature.


A team of theoretical physicists from the University of Exeter has pioneered a new technique to create tunable artificial magnetic fields, which enable photons to mimic the dynamics of charged particles in real magnetic fields.

The team believes that the new research has been published in the leading journal Nature photonics, May have important implications for future photonic devices as it provides a new way of manipulating light below the diffraction limit.

When charged particles, like electrons, pass through a magnetic field, they feel a Lorentz force due to their electric charge, which bends their trajectory around the magnetic field lines.

This Lorentz force is responsible for many fascinating events, ranging from the beautiful Northern Lights to the famous quantum-hall effect whose discovery was awarded the Nobel Prize.

However, because photons do not carry an electric charge, they cannot be directly controlled using real magnetic fields because they do not experience a Lorentz force; A serious limitation that is set by the fundamental laws of physics.

Research teams have shown that it is possible to create artificial magnetic fields for light by distorting honeycomb metasurfaces — ultra-thin 2-D surfaces, which are engineered to create structures at a much smaller scale than the wavelength of light.

The Exeter team was inspired by a remarkable discovery ten years ago where it was shown that electrons circulating through a precipitated graphene membrane behaved as if they were subjected to a large magnetic field.

The major drawback with this strain engineering approach is that to tune the artificial magnetic field the strain pattern needs to be modified with precision, which is extremely challenging, if not impossible, to do with photonic structures.

Exeter physicists have proposed an elegant solution to overcome this fundamental lack of tunability.

The study’s lead scientist and author, Charlie-Ray Mann, explains: “These metasurfs support hybrid light-matter stimuli, called polaritons, that are trapped on the metasurface.

“They are then deflected by deformations in the metasurface in a similar way to how magnetic fields deflect charged particles.

“By exploiting the hybrid nature of polaritons, we show that you can tune the artificial magnetic field by modifying the actual electromagnetic environment around the metasurface.”

For the study, researchers referred to the metasurface as a photo-cavity between two mirrors — and demonstrated that the individual could only tune the artificial magnetic field by changing the width of the photonic cavity, thereby modifying the distortion in the metasurface. Is required. .

Charlie said: “We have also demonstrated that you can completely switch the artificial magnetic field to the width of a critical cavity without removing distortion in the metasurface, something that is simulated by graphene or graphene This is impossible to do in any system.

“Using this mechanism you can bend the trajectory of polarization using a tunable Lorentz-like force and observe Landau quantification of polarity cyclotron orbitals, in direct analogy with what happens to charged particles in real magnetic fields. Huh.

“Furthermore, we have shown that you can change the Polariton Landau level spectrum significantly by simply changing the cavity width.”

The principal supervisor of the study was Dr. Eros Mariani said: “To be able to simulate phenomena with photons that are generally considered exclusive to charged particles is attractive from a fundamental point of view, but it can also have significant implications for photonics. Applications. .

“We are excited to see how far this discovery goes, as it contains many intriguing questions that can be explored in many different experimental platforms in the electromagnetic spectrum.”


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more information:
Mann, C., Horsley, SAR & Mariani, E. Tunable pseudo-magnetic fields for polar regions in strained metasurfs. met. Photonics (2020). doi.org/10.1038/s41566-020-0688-8, www.nature.com/articles/s41566-020-0688-8

Provided by the University of Exeter

Quotes: Physicists ‘move to behave like electrons using’ synthetic ‘magnetic fields (2020, 14 September)’ Photons on 14 September 2020 https://phys.org/news/2020-09-physicists-photons-eetrons -synthetic- retrieved from magnetic.html

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