Unconventional hysteretic transition in a charge density wave

TL;DR

This study reports an unprecedented hysteretic transition in EuTe4, a quasi-2D material, characterized by a record-wide temperature hysteresis and a unique phase switching mechanism within the charge-density-wave state.

Contribution

It reveals an unconventional hysteretic transition driven by interlayer CDW phase switching, challenging existing theories on metastability in density wave systems.

Findings

Hysteresis loop width exceeds 400 K, a record among crystalline solids.

Transition occurs without change in CDW periodicity.

Hysteresis involves switching of CDW phases between layers.

Abstract

Hysteresis underlies a large number of phase transitions in solids, giving rise to exotic metastable states that are otherwise inaccessible. Here, we report an unconventional hysteretic transition in a quasi-2D material, EuTe4. By combining transport, photoemission, diffraction, and x-ray absorption measurements, we observed that the hysteresis loop has a temperature width of more than 400 K, setting a record among crystalline solids. The transition has an origin distinct from known mechanisms, lying entirely within the incommensurate charge-density-wave (CDW) phase of EuTe4 with no change in the CDW modulation periodicity. We interpret the hysteresis as an unusual switching of the relative CDW phases in different layers, a phenomenon unique to quasi-2D compounds that is not present in either purely 2D or strongly-coupled 3D systems. Our findings challenge the established theories on metastable states in density wave systems, pushing the boundary of understanding hysteretic transitions in a broken-symmetry state.