<p>Non-Hermitian physics has recently transformed our understanding of topology by uncovering a range of effects that are unique to systems with gain and loss. The realization of non-Hermitian topology in strongly coupled light–matter systems not only offers degrees of freedom for the enhanced manipulation of topological phenomena, but is also promising for developing on-chip active photonic devices. Exciton–polaritons—strongly coupled quasiparticles from excitons and photons—emerge as a promising candidate with intrinsic non-Hermitian features. However, limited by the challenges in achieving non-reciprocity, the experimental observation of non-Hermitian topology and its associated transport features has remained elusive. Here we experimentally demonstrate the non-Hermitian topology of exciton–polaritons induced by a twist degree of freedom in a liquid-crystal-filled CsPbBr<sub>3</sub> perovskite microcavity at room temperature. The geometric twist between birefringent perovskites and liquid crystals acts as a degree of freedom to tailor the polaritonic complex spectra, leading to non-Hermitian bands with spectral winding topology and non-reciprocity. Furthermore, the induced non-Hermitian topology gives rise to the non-Hermitian exciton–polariton skin effect in real space, manifesting as polariton accumulation at open boundaries. Our findings open new perspectives on tunable non-Hermitian phenomena and the development of on-chip polaritonic devices with enhanced functionalities.</p>

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Twist-induced non-Hermitian topology of exciton–polaritons

  • Jie Liang,
  • Hao Zheng,
  • Feng Jin,
  • Ruiqi Bao,
  • Kevin Dini,
  • Jiahao Ren,
  • Yuxi Liu,
  • Mateusz Król,
  • Elena A. Ostrovskaya,
  • Eliezer Estrecho,
  • Baile Zhang,
  • Timothy C. H. Liew,
  • Rui Su

摘要

Non-Hermitian physics has recently transformed our understanding of topology by uncovering a range of effects that are unique to systems with gain and loss. The realization of non-Hermitian topology in strongly coupled light–matter systems not only offers degrees of freedom for the enhanced manipulation of topological phenomena, but is also promising for developing on-chip active photonic devices. Exciton–polaritons—strongly coupled quasiparticles from excitons and photons—emerge as a promising candidate with intrinsic non-Hermitian features. However, limited by the challenges in achieving non-reciprocity, the experimental observation of non-Hermitian topology and its associated transport features has remained elusive. Here we experimentally demonstrate the non-Hermitian topology of exciton–polaritons induced by a twist degree of freedom in a liquid-crystal-filled CsPbBr3 perovskite microcavity at room temperature. The geometric twist between birefringent perovskites and liquid crystals acts as a degree of freedom to tailor the polaritonic complex spectra, leading to non-Hermitian bands with spectral winding topology and non-reciprocity. Furthermore, the induced non-Hermitian topology gives rise to the non-Hermitian exciton–polariton skin effect in real space, manifesting as polariton accumulation at open boundaries. Our findings open new perspectives on tunable non-Hermitian phenomena and the development of on-chip polaritonic devices with enhanced functionalities.