Parity–time reversal symmetry (PT symmetry) in non-Hermitian systems realizes spontaneous symmetry breaking, thereby leading to counterintuitive phenomena. A coupled system with antisymmetric gain/loss profiles is required to introduce PT symmetry into photonics. As photons are intrinsically non-interactive, selection of two-photonic components is inevitable to mediate indirect coupling via near-fields. Remarkably, exciton–polaritons (the hybrid nature of excitons and photons) are directly interactive via excitonic components; however, the features of direct coupling between exciton–polariton modes have not been investigated so far. Here we demonstrate that such direct coupling can remodel conventional photonic platforms of non-Hermitian systems into polaritonic platforms with a single component; thus improving the degrees of freedom of both integration and design for the coupled system. We focused on the sixfold-symmetric microcavity to exploit degenerated photonic modes. By employing direct coupling with loss modulation, we observed room-temperature polaritonic PT symmetry with a phase transition from unbroken to broken, revealing the lowest threshold of polariton condensates in non-Hermitian degeneracies despite increasing loss.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.
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We thank LG Innotek for providing the wire samples. This work was supported by the National Research Foundation (grant nos. 2019R1A2B5B03070642 and 2020M3E4A1080112) of the Korean government, and the Samsung Science and Technology Foundation under project no. SSTF-BA1602-05.
The authors declare no competing interests.
Peer review information Nature Photonics thanks Zheng Sun and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Song, H.G., Choi, M., Woo, K.Y. et al. Room-temperature polaritonic non-Hermitian system with single microcavity. Nat. Photon. 15, 582–587 (2021). https://doi.org/10.1038/s41566-021-00820-z