Emergent Cooperative Superstructures via Order-Disorder Kinetics in Molecule-Intercalated NbSe2

TL;DR

This paper discovers a cooperative superstructure in molecule-intercalated NbSe2, where molecular ordering induces a superlattice in the host, with slow order-disorder kinetics enabling thermally programmable heterointerface engineering.

Contribution

It reveals a new cooperative superstructure phase driven by molecular ordering in NbSe2, highlighting slow kinetics as a key factor for thermally controllable superlattice formation.

Findings

Molecular ordering induces a superstructure in NbSe2.

The transition exhibits slow order-disorder kinetics.

The superstructure can be thermally programmed.

Abstract

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.