The design of quantum states at heterointerfaces has enabled a variety of emergent phenomena. Among them, molecular intercalation superlattices have attracted attention as tunable hybrid materials, formed by inserting organic molecules into van der Waals crystals, where molecular structure and chemistry provide new degrees of freedom. Traditionally, the intercalated molecules have been regarded as inactive spacers, while possible molecular ordering and its impact on the host lattice have remained largely unexplored. Here, we report the discovery of a cooperative superstructure (CSS) phase in molecule intercalated NbSe2, where ordering of the guest molecules induce a concomitant superstructure in the NbSe2 host lattice, characterized by a moir\'e structure due to incommensurability between the molecular layer and the inorganic lattice. Synchrotron X-ray diffraction reveals the emergence of CSS phase, accompanied by crystal symmetry lowering. Complementary resistivity and thermal-quench measurements show that the transition is governed by unusually slow order-disorder kinetics, so that the CSS phase can be selectively accessed under standard laboratory cooling rates. This kinetic behavior arises from slow molecular dynamics coupled to the host lattice, contrasting with fast charge or magnetic ordering in inorganic solids. Our findings establish molecular ordering as a route for engineering heterointerfaces, enabling thermally programmable superstructures.
@article{arxiv.2601.07216,
title = {Emergent Cooperative Superstructures via Order-Disorder Kinetics in Molecule-Intercalated NbSe2},
author = {Taiga Ueda and Hideki Matsuoka and Shungo Aoyagi and Shunsuke Kitou and Yijin Zhang and Fumihiko Kimura and Kenta Hagiwara and Masato Sakano and Takahiro Iwagaki and Yuiga Nakamura and Kyoko Ishizaka and Tomoki Machida and Masayuki Suda and Taka-hisa Arima and Naoya Kanazawa},
journal= {arXiv preprint arXiv:2601.07216},
year = {2026}
}