Physicists "trick" photons into behaving like electrons using a "synthetic" magnetic field

September 14, 2020

Scientists have discovered an elegant way of manipulating light using a "synthetic" Lorentz force -- which in nature is responsible for many fascinating phenomena including the Aurora Borealis.

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

The team believe the new research, published in leading journal Nature Photonics, could have important implications for future photonic devices as it provides a novel 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 curves their trajectory around the magnetic field lines.

This Lorentz force is responsible for many fascinating phenomena, 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 straightforwardly controlled using real magnetic fields since they do not experience a Lorentz force; a severe limitation that is dictated by the fundamental laws of physics.

The research team have shown that it is possible to create artificial magnetic fields for light by distorting honeycomb metasurfaces -- ultra-thin 2D surfaces that are engineered to have structure on a scale much smaller than the wavelength of light.

The Exeter team were inspired by a remarkable discovery ten years ago, where it was shown that electrons propagating through a strained graphene membrane behave 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 one is required to modify the strain pattern with precision, which is extremely challenging, if not impossible, to do with photonic structures.

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

Charlie-Ray Mann, the lead scientist and author of the study, explains: "These metasurfaces, support hybrid light-matter excitations, called polaritons, which are trapped on the metasurface.

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

"By exploiting the hybrid nature of the polaritons, we show that you can tune the artificial magnetic field by modifying the real electromagnetic environment surrounding the metasurface."

For the study, the researchers embedded the metasurface between two mirrors -- known as a photonic cavity -- and show that one can tune the artificial magnetic field by changing only the width of the photonic cavity, thereby removing the need to modify the distortion in the metasurface.

Charlie added: "We have even demonstrated that you can switch off the artificial magnetic field entirely at a critical cavity width, without having to remove the distortion in the metasurface, something that is impossible to do in graphene or any system that emulates graphene.

"Using this mechanism you can bend the trajectory of the polaritons using a tunable Lorentz-like force and also observe Landau quantization of the polariton cyclotron orbits, in direct analogy with what happens to charged particles in real magnetic fields.

"Moreover, we have shown that you can drastically reconfigure the polariton Landau level spectrum by simply changing the cavity width."

Dr Eros Mariani, the lead supervisor of the study, said: "Being able to emulate phenomena with photons that are usually thought to be exclusive to charged particles is fascinating from a fundamental point of view, but it could also have important implications for photonics applications.

"We're excited to see where this discovery leads, as it poses many intriguing questions which can be explored in many different experimental platforms across the electromagnetic spectrum."

University of Exeter

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to