  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.
