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arXiv · 2308.03195

Terahertz chiral sub-wavelength cavities breaking time-reversal symmetry via ultra-strong light-matter interaction

Johan Andberger·Lorenzo Graziotto·Luca Sacchi·Mattias Beck·Giacomo Scalari·Jérôme Faist
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Abstract

We demonstrate terahertz chiral sub-wavelength cavities that break time-reversal symmetry by coupling the degenerate linearly polarized modes of two orthogonal sets of nano-antenna arrays using the inter-Landau level transition of a two-dimensional electron gas in a perpendicular magnetic field, realizing normalized light-matter coupling rates up to $\Omega_R/\omega_{\mathrm{cav}} = 0.78$ with a dispersion that is modified by the parasitic capacitive coupling between the orthogonal antennas. The deep sub-wavelength confinement of the nano-antennas means that the ultra-strong coupling regime can be reached even with a small number of carriers compared to Fabry-Perot cavities, making it viable to be used with a variety of 2D materials. The non-degenerate circularly polarized ground state was only obtained after carefully optimizing the optical design to minimize the parasitic coupling to linearly polarized light.

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Johan Andberger, Lorenzo Graziotto, Luca Sacchi, Mattias Beck, Giacomo Scalari, Jérôme Faist. 2023-08-06. Terahertz chiral sub-wavelength cavities breaking time-reversal symmetry via ultra-strong light-matter interaction. https://doi.org/10.1103/physrevb.109.l161302

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