Room-temperature multistage metastability in a moiré superstructure

Charge density waves (CDWs) offer versatile platforms for accessing metastable states due to their sensitivity to external stimuli. However, most metastable CDW states are stabilized only at low temperatures, limiting their practical utility. In this study, we report the observation of electrically driven, room-temperature, nonvolatile metastable states in the bulk form of EuTe4, a recently discovered compound that hosts an innate moiré superlattice characterized by the stacking of incommensurate monolayer and bilayer CDWs. Systematic transport measurements reveal discrete resistivity plateaus and strong electric-field sensitivity, with a large number of metastable states readily induced across a wide temperature window within a giant hysteresis loop, making them well-suited for high-temperature, multi-bit memory applications. By integrating photoemission spectroscopy, diffraction, and in-situ transport measurements, we uncover that these metastable states are characterized by a suppression of the original CDW amplitude and a reduction in correlation length, pointing to a unique electric-field-induced switching of out-of-plane CDW phases in the moiré superstructure. Our findings provide critical insights into metastable phenomena in moiré systems with stacked electronic orders and establish EuTe4 as a promising platform for developing room-temperature, multi-bit memory devices. Switchable metastable states, such as charge density waves, could serve as a building block for memory applications. Here, using a suite of transport, photoemission, and diffraction measurements, Lv, Su, Zong and coauthors demonstrate the existence of electrically driven non-volatile metastable states in the bulk form of EuTe4 at room temperature.