Anomalous charge density wave in a two-dimensional superatomic superconductor

The spatial modulation of electron density into a wave-like pattern, known as charge density wave (CDW), represents a fundamental quantum state that often coexists with superconductivity, quantum Hall states and axion insulating phases. Conventional CDWs are mediated by longitudinal acoustic phonons, exhibit picometer-scale lattice distortions (10^-12-10^-11m), and typically vanish upon approaching the atomic limit. Here, we report a series of anomalous CDW behaviors in the 2D superatomic superconductor Au₆Te₁₂Se₈. Remarkably, its CDW is governed by transverse phonons and exhibits a real-space displacement of ~ 4 Ångström, which is an order of magnitude larger than that in conventional CDW. Furthermore, we observe a dimensional response persisting up to micrometer-scale thickness, a regime where other materials are already considered as bulk. Through liquid helium-temperature transmission electron microscopy, ultrafast pump-probe spectroscopy and transport measurements, we demonstrate a prominent enhancement of the CDW transition temperature (T_CDW) from < 2 K in the bulk to 110 K upon approaching the "superatomic limit". Our findings not only reveal anomalous facets of both CDW and superatomic materials, but the competition between this anomalous CDW and superconductivity opens avenues for exploring unconventional electron-phonon interactions.