The interaction between organic cations and inorganic metal halide octahedral units strongly affects the properties of organic–inorganic hybrid metal halides. The “soft” property of the lattice provides the possibility of its strong exciton–phonon interaction. Here we report one-dimensional (1D) lead-free chiral organic–inorganic hybrid metal halide single crystals of (R/S)-methylbenzylamine bismuth iodide (R/S-MBA)2Bi2I8, which exhibits a high level of octahedral bond distortion. The introduction of chiral amines leads to a strong chiroptical response in the range of 200–600 nm. The strong exciton–phonon coupling can be observed through the coherent oscillation spectrum of transient absorption dynamics at room temperature. The coherent phonon oscillation frequencies are ∼97 and ∼130 cm–1, corresponding to the symmetrical stretching or bending of the Bi–I octahedron. Our work provides new insights for the study of exciton–phonon coupling in 1D chiral hybrid metal halides.

Strong light-matter interactions in two-dimensional transition metal dichalcogenides (TMDCs) with robust spin-valley degrees of freedom open up the prospect of valleytronic devices. A thorough understanding on the dynamics of the valley polarizations in the strong coupling regime is urgently required. Here, multiple polarized TMDCs-SPPs hybrid systems were constructed by combining monolayer WS2 flakes to linear, circular, and spiral Ag gratings, resulting in linear and circular polarized modulation on the coherent hybrid states, respectively. Particularly, valley polaritons can be tailored asymmetrically by chiral strong coupling regime. Furthermore, the dynamics of the polarized polaritons were directly analyzed by transient absorption (TA) measurement. Both of the linear and circular polarization difference in the TA spectra can be retained for a remarkable long time, leading to a polarized PL even at room temperature. More importantly, in the chiral strong coupled WS2-spiral Ag grating devices, the mechanism of the asymmetrical valley-polarized PL (p σ+ = 14.9% and p σ- = 10.8%) is proved by the opposite valley polarization dynamics in the circularly polarized TA spectra. The multiple polarization modulation in monolayer TMDCs-SPPs strong coupling devices could provide a viable route toward multiple polarization polaritonic devices.

Half-light and half-matter exciton polaritons have demonstrated profound impacts on coherent quantum phenomena. Two-dimensional (2D) organic−inorganic perovskite semiconductors, exhibiting large exciton binding energy and spin-based behavior, are an excellent platform for the study of exciton polaritons at room temperature. However, the implementation of these fascinating coherent phenomena is still constrained by the lack of an understanding of the crucial polariton-polariton interaction effects. Here, an experimental observation of spin-dependent polariton-polariton interactions in a prototype 2D organic−inorganic perovskite microcavity by circularly polarization-resolved transient absorption (TA) measurements is reported. A power-dependent blue shift of the lower polariton bands with the same spin is clearly revealed, whereas the energy band of the polariton bands with the opposite spin is almost not changed. Spectacularly, it is found that the energy band blue shift mainly takes place before the spin depolarization, which provides accurate evidence for the spin-dependent polariton-polariton interactions. Furthermore, the strong coherent polariton-phonon coupling of perovskite microcavity has also been detected firstly in ultrafast TA dynamics. These results demonstrate that microcavity polaritons inheriting the matter properties from their excitonic constituents exhibit strong nonlinear interactions and pave the way for realizing coherent quantum phenomena at room temperature.