Unconventional charge density wave in Kagome metal BaFe2Al9

Liucheng Chen; Mingwei Ma; Xiaohui Yu; Fang Hong

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arXiv · 2507.16325

Unconventional charge density wave in Kagome metal BaFe2Al9

Liucheng Chen·Mingwei Ma·Xiaohui Yu·Fang Hong

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Abstract

The charge density wave (CDW) is a macroscopic quantum state characterized by long-range lattice distortion and modulated charge density. Conventionally, CDWs compete with other electronic orders (e.g. superconductivity) and are suppressed under hydrostatic pressure. Intriguingly, the Kagome-variant metal BaFe2Al9, crystallized in a three-dimensional structure, exhibits pressure-enhanced CDW ordering, where the transition temperature (TCDW) rises from ~110 K to room temperature near 3.6 GPa. The lattice structure was checked by both powder and single crystal x-ray diffraction (XRD). The XRD data reveals an abnormal lattice expansion along a axis near 4-5 GPa upon compression. The strongly suppressed diffraction intensity and splitting diffraction spots from single crystal indicates cracking and breakdown to smaller pieces, indicative of an intrinsic first-order transition character. This anomalous response implies a CDW mechanism dominated by electron-electron and/or electron-phonon correlations, distinct from Fermi-surface nesting in conventional systems. Concomitant dome-shaped pressure-dependent resistance suggests competing electronic phases. Our work establishes BaFe2Al9 as a 3D Kagome platform with unconventional CDW behavior and strong electron-phonon coupling, which provides an alternative platform to explore the electron correlation induced exotic electronic states and other potential emergent quantum phenomenon.

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Liucheng Chen, Mingwei Ma, Xiaohui Yu, Fang Hong. 2025-07-22. Unconventional charge density wave in Kagome metal BaFe2Al9. https://arxiv.org/abs/2507.16325

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