Soliton disentangling and ferroelectric hysteresis in reconstructed moire superlattices

TL;DR

This paper investigates the lattice dynamics and ferroelectric properties of reconstructed moire superlattices, revealing phonon splitting, hysteresis, and demonstrating a ferroelectric tunneling junction with high electroresistance, advancing optoelectronic memory technology.

Contribution

It uncovers phonon splitting and ferroelectric hysteresis in moire superlattices and demonstrates a ferroelectric tunneling junction, providing new insights into lattice symmetry and potential memory devices.

Findings

Phonon splitting at strain soliton networks is tunable by displacement field.

Ferroelectric hysteresis loops are observed in phonon evolution.

A moire ferroelectric tunneling junction with ~10^4 tunneling electroresistance is demonstrated.

Abstract

Moire materials, created by lattice-mismatch or/and twist-angle, have spurred great interest in excavating novel quantum phases of matter. Latterly, emergent interfacial ferroelectricity has been surprisingly found in spatial inversion symmetry broken systems, such as rhombohedral-stacked bilayer transition metal dichalcogenides (TMDs). However, the evolution of moire superlattices corresponding to polarization switching and hysteresis is still unclear, which is crucial for giving insight into the interplay between lattice symmetry and band topology, as well as developing optoelectronic memory devices. Here we report on the observation of phonon splitting at strain soliton networks in reconstructed moire superlattices, arising from the twisting and relaxing induced strong three-fold rotational symmetry (C3) breaking. The interval of phonon splitting is tunable by a perpendicular displacement field and exhibits ferroelectric-related hysteresis loops. These phonon evolution features are attributed to the contribution of moire solitons disentangling and lattice viscosity during the motion of domain walls. Moreover, we demonstrate a proof-of-principle moire ferroelectric tunneling junction, whose barrier is modified by net polarization with a tunneling electroresistance of ~10^4. Our work not only reveals the lattice dynamics of moire solitons but also presents a potential pathway for future ferroelectric-based optoelectronic memory devices.