Room-temperature multistage metastability in a moir\'e superstructure

TL;DR

This study demonstrates room-temperature, electrically driven metastable states in EuTe4 with a moiré superstructure, revealing potential for high-temperature multi-bit memory applications through electric-field-induced phase switching.

Contribution

It reports the discovery of stable, nonvolatile metastable states at room temperature in EuTe4, driven by electric fields, a significant advancement over low-temperature metastability in charge density wave systems.

Findings

Discrete resistivity plateaus observed under electric fields

Metastable states induced across a wide temperature range

Metastability characterized by suppression of CDW amplitude and correlation length

Abstract

Metastability is fundamental not only to phase ordering and transitions, but also to a broad range of modern technologies, from memory devices to metallic glasses. In condensed-matter physics, 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 EuTe$_4$, a recently discovered compound that hosts an innate moir\'e 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 do not stem from conventional mechanisms such as the emergence of new ordered phases or changes in incommensurate periodicity. Instead, they 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 moir\'e superstructure. Our findings not only provide critical insights into metastable phenomena in moir\'e systems with stacked electronic orders but also establish EuTe$_4$ as a promising platform for developing room-temperature, multi-bit memory devices.