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arXiv · 2610.30964

Intensity-driven Mott-like transition in a 2D Ruddlesden-Popper perovskite

Koushik Mondal·Amit Haldar·Indrajit Mondal·Arpita Dutta·Himanshu Bhatt·Biswajit Mahata·Soumili Banerjee·Hirendra Nath Ghosh·Satyaprasad P Senanayak·Shovon Pal
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Abstract

Two-dimensional Ruddlesden-Popper-type halide perovskites have emerged as promising cutting-edge nonlinear optical materials due to their strong excitonic effects and carrier-density-dependent optical responses. In this work, we investigate the nonlinear optical properties and ultrafast carrier dynamics of (BA)$_2$PbI$_4$ under infrared excitation, resonant with the two-photon energy of its excitonic transition. Using a nonlinear femtosecond Z-scan measurement with a 1030\,nm pump pulse, we observe a pronounced intensity-dependent evolution of the nonlinear absorption coefficient and the refractive index. With increasing pump intensity, a switch from saturable absorption to reverse saturable absorption emerges, suggesting an intensity-driven Mott-like transition. To elucidate the underlying carrier dynamics, intensity-dependent transient absorption spectroscopy was performed under the same excitation intensities. This reveals a long-lived charge carrier population above the estimated Mott density, reflecting a clear phase transition from an exciton-dominated regime to a dense electron-hole plasma regime. Moreover, such an intensity-driven, high, and switchable nonlinear optical response, along with a Mott-like transition under infrared pulse excitation, makes the 2D (BA)$_2$PbI$_4$ perovskites suitable for all-optical operation in the infrared regime.

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Koushik Mondal, Amit Haldar, Indrajit Mondal, Arpita Dutta, Himanshu Bhatt, Biswajit Mahata, Soumili Banerjee, Hirendra Nath Ghosh, Satyaprasad P Senanayak, Shovon Pal. 2026-10-22. Intensity-driven Mott-like transition in a 2D Ruddlesden-Popper perovskite. https://arxiv.org/abs/2610.30964

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