New Publication: Tunable pseudo-magnetic fields for polaritons in strained metasurfaces

Congratulations to final year PhD student Charlie-Ray Mann whose theory paper, entitled ‘Tunable pseudo-magnetic fields for polaritons in strained metasurfaces’, has been published in the prestigious journal Nature Photonics.

The work has also been featured on the University of Exeter’s news website.

Charlie-Ray Mann, the lead scientist and author of the study, explains:

Charlie-Ray Mann- lead scientist and author of the paper published in Nature Photonics

The interaction between charged particles and magnetic fields gives rise to some of the most fascinating phenomena in physics, ranging from the beautiful Aurora Borealis to the famous quantum-Hall effect. Unfortunately, because photons do not have an electric charge they are inert to real magnetic fields as they do not experience a Lorentz force.

Taking inspiration from graphene physics, we have shown that you can generate `artificial’ magnetic fields for light by distorting honeycomb metasurfaces in a specific way. These distortions generate a ‘synthetic’ Lorentz force which can deflect the surface polaritons into effective cyclotron orbits, and for larger distortions one can also observe Landau quantization of the polaritons — phenomena once thought to be exclusive to charged particles.

However, the main drawback with this approach is that to change the artificial magnetic field one is usually required to modify the distortion in the lattice. This is extremely challenging, if not impossible to do with photonic structures, hindering our ability to tune the artificial magnetic field after the structure has been fabricated — that is, the artificial magnetic fields are usually fixed by design.

In this theoretical work we have proposed an alternative mechanism to tune the artificial magnetic fields, which requires no change to the metasurface distortion. By exploiting the hybrid light-matter character of the surface polaritons, we show that one can tune the artificial magnetic field by modifying the real electromagnetic environment surrounding the metasurface.

Specifically, we’ve shown that by embedding the metasurface inside a photonic cavity or waveguide, one can tune the artificial magnetic field by modifying a single external parameter: the cavity width. In fact, we’ve even demonstrated that you can switch off the artificial magnetic 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 new mechanism you can bend the trajectory of the polaritons using a tunable Lorentz-like force that can be switched on/off, and you can drastically reconfigure the polariton Landau level spectrum by simply changing the cavity width.

Earlier this year, Charlie-Ray Mann was awarded a £5,000 prize from the Rank Prize Funds 2020.

Charlie-Ray Mann awarded £5,000 prize from the Rank Prize Funds 2020

Charlie-Ray Mann pictured with 1985 Nobel Prize winner Klaus von Klitzing at the 69th Lindau Nobel Laureate Meeting

Congratulations to final year PhD student Charlie-Ray Mann who has been awarded a £5,000 prize from the Rank Prize Funds.


The Trustees of the Rank Prize Funds decided to offer a number of awards, each worth £5,000, for final year PhD students in UK universities who have a major commitment to teaching and research in optoelectronics, and who are likely to embark on a successful research career.  The scheme was set up to support students through the disruptions caused by the coronavirus pandemic. Every university in the UK was invited to nominate up to two final year PhD students from different departments or schools.


The University of Exeter nominated Charlie-Ray Mann as the candidate from the School of Physics and Astronomy, and he was awarded the prize by the Optoelectronics Advisory Committee. His PhD work, under the supervision of Dr Eros Mariani and Prof Bill Barnes, focuses on the theoretical investigation of novel Dirac and topological polaritons supported by metasurfaces embedded in photonic cavities. Charlie’s research has been published in several top-level journals, including Nature Photonics (2020) and Nature Communications (2018).

Henry Fernández gives talk at Nanometa 2019

Fourth year CDT PGR Henry Fernández gave a talk at the prestigious Nanometa 2019 conference in Seefield, Austria on 5th January 2019.  Nanometa aims to bring together the international Nanotechnology, Photonics and Materials research communities where most recent and challenging results and plans are discussed in the informal setting on a glorious mountaineering resort.

As the conference is very competitive, it is unusual for PhD students to give a talk. Henry spoke on “Electrical control of the Rabi splitting in a strongly coupled semiconductor microcavity”.

Fourth years PGRs Carlota Ruiz de Galarreta, Charlie-Ray Mann and Tom Collier also attended.

Henry has also been invited to give a talk in a symposium organised by the Rank Prize Funds, on the topic of two dimensional semiconductors for optoelectronics- watch this space!