Ultrafast imaging of polariton propagation and interactions

• Published in: Nature communications Vol. 14; no. 1; p. 3881
• Main Authors: Xu, Ding, Mandal, Arkajit, Baxter, James M., Cheng, Shan-Wen, Lee, Inki, Su, Haowen, Liu, Song, Reichman, David R., Delor, Milan
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30.06.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 140/125; 639/301; 639/624; Diagnostic Imaging; Diffusion; Energy flow; Excitons; Humanities and Social Sciences; Hybridization; Hybridization, Genetic; Light microscopy; Microcavities; Momentum; Motion; multidisciplinary; Optical microscopy; Perovskites; Phonons; Photons; Polaritons; Propagation; Room temperature; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-39550-x

Semiconductor excitations can hybridize with cavity photons to form exciton-polaritons (EPs) with remarkable properties, including light-like energy flow combined with matter-like interactions. To fully harness these properties, EPs must retain ballistic, coherent transport despite matter-mediated interactions with lattice phonons. Here we develop a nonlinear momentum-resolved optical approach that directly images EPs in real space on femtosecond scales in a range of polaritonic architectures. We focus our analysis on EP propagation in layered halide perovskite microcavities. We reveal that EP–phonon interactions lead to a large renormalization of EP velocities at high excitonic fractions at room temperature. Despite these strong EP–phonon interactions, ballistic transport is maintained for up to half-exciton EPs, in agreement with quantum simulations of dynamic disorder shielding through light-matter hybridization. Above 50% excitonic character, rapid decoherence leads to diffusive transport. Our work provides a general framework to precisely balance EP coherence, velocity, and nonlinear interactions. Exciton-polaritons are part-light part-matter states in semiconductors. Here the authors leverage momentum-resolved optical microscopy to image ballistic and diffusive propagation of exciton-polaritons on femtosecond scales.