PHYSICAL REVIEW APPLIED 18, 014079 (2022) Mie Exciton-Polariton in a Perovskite Metasurface Khalil As’ham , 1 Ibrahim Al-Ani , 1 Wen Lei, 2 Haroldo T. Hattori , 1 Lujun Huang , 1, * and Andrey Miroshnichenko 1, † 1 School of Engineering and Information Technology, University of New South Wales at Canberra, Northcott Drive, Canberra, Australian Capital Territory 2610, Australia 2 Department of Electrical Engineering, School of Engineering, University of Western Australia, 35 Stirling Highway, Perth, Washington 6009, Australia (Received 2 April 2022; revised 16 May 2022; accepted 25 May 2022; published 29 July 2022) Exciton-polariton arising from strong light-matter interaction between exciton and optical cavity has attracted considerable attention due to its potential applications in Bose-Einstein condensation, low- threshold lasing, and slow light. In recent years, two-dimensional lead halide perovskite has emerged as an ideal candidate for realizing exciton polariton at room temperature because it has large exciton binding energy and quantum yield. Here, we demonstrate that strong coupling could be enabled with a perovskite metasurface that supports multipolar Mie resonance, including magnetic quadrupole dominant, anapole, and toroidal resonances. For an array of perovskite nanodisks, the strong coupling behavior between these resonances and exciton is confirmed by the anticrossing features in absorption spectra mapping, while the Rabi splitting is increased from 230.7 meV in magnetic quadrupole-exciton strong coupling to 253 meV in both anapole-exciton and toroidal-exciton strong coupling. The enhanced Rabi splitting is attributed to the stronger field localization within the perovskite instead of within the air gap. In addition, we find that the Rabi splitting depends on the oscillatory strength of the exciton mode and can then be boosted to 362 meV in anapole-exciton strong coupling. Our results provide promising ways to improve the performance of optoelectronic devices such as low-threshold lasers and slow-light devices. DOI: 10.1103/PhysRevApplied.18.014079 I. INTRODUCTION Exciton polaritons, formed by the interaction between excitons and light, are critical quasiparticles used in different applications such as Bose-Einstein condensa- tion, superfluidity, quantum vortices, low-threshold lasing, sensing, and slow light [1–5]. So far, most studies on exciton polaritons focus on conventional inorganic semi- conductors such as gallium arsenide (GaAs) and cadmium telluride (CdTe) [6]. However, observing exciton polari- tons in inorganic materials at room temperature is chal- lenging because of their small excitonic energy, weak oscillator strength, and large size [7,8]. Although efforts to implement such devices that operate at room temper- ature have been made with inorganic and organic mate- rials with high excitonic binding energy such as gallium nitride (GaN), zinc oxide (ZnO), and organic semiconduc- tors, they still suffer from mismatched thermal expansion coefficients, require high-temperature epitaxial techniques, and have large sizes [6–9]. Recently, pushing the inter- action between the exciton and electromagnetic waves down to the nanoscale at room temperature has drawn * ljhuang@mail.sitp.ac.cn † andrey.miroshnichenko@adfa.edu.au much attention due to its various applications that lead to the implementation of unconventional nanophotonic devices [10]. In principle, surface plasmon polariton nanostructures have the ability to confine light in tiny volumes, potentially being an ideal platform to explore the strong-coupling regime [11]. Of note, the interaction between plasmon modes and exciton in molecules, quantum dots, and transi- tion metal dichalcogenides (TMDCs) have been observed at room temperature at the nanoscale [12–18]. However, both molecules and quantum dots can hardly control the excitonic orientation [17]. Moreover, the metallic plas- monic structures suffer from high absorption and large Ohmic losses [10,19], which may degrade the device’s performance operating at considerable pumping power. In recent years, hybrid organic-inorganic lead halide perovskites materials have emerged as an excellent plat- form to realize photonic and optoelectronic devices with superior performance due to their salient properties, such as high optical absorption efficiency, broad resonance tun- ability, large excitonic binding energy, cheap fabrication techniques, and low rates of nonradiative recombina- tion compared with conventional semiconductor materials [2,3,20–25]. These features make it possible to observe the strong-coupling regime at room temperature and have led 2331-7019/22/18(1)/014079(10) 014079-1 © 2022 American Physical Society