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arXiv · 2610.28877

Ultrafast and Anisotropic Exciton Transport in Layered NbOI$_2$

Salman Ahsanullah·Neema Rafizadeh·Hui Zhao
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Abstract

Ferroelectric layered semiconductors provide a unique platform for exploring coupled excitonic and electronic phenomena in reduced dimensions. Here, exciton transport in layered NbOI$_2$ is investigated using transient absorption microscopy. Ultrafast and strongly anisotropic exciton diffusion is observed. The diffusion coefficient of about 160 cm$^2$ s$^{-1}$ along the nonpolar crystal axis is among the highest reported for van der Waals semiconductors. The transport exhibits an approximately twofold in-plane anisotropy between the polar and nonpolar directions, reflecting the intrinsic low-symmetry crystal structure of NbOI$_2$. The environmental stability of NbOI$_2$ is further investigated, and fabrication and encapsulation conditions required to achieve long-term sample stability are identified. These results establish NbOI$_2$ as a promising platform for studying anisotropic exciton transport and highlight the critical role of interface protection in air-sensitive van der Waals materials.

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Salman Ahsanullah, Neema Rafizadeh, Hui Zhao. 2026-10-20. Ultrafast and Anisotropic Exciton Transport in Layered NbOI$_2$. https://arxiv.org/abs/2610.28877

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