Sliding ferroelectricity arises from non-centrosymmetric stacking in van der Waals layered materials, where out-of-plane polarization can be reversed by in-plane sliding between adjacent layers. A key open question is how a vertical electric field drives such interlayer sliding and whether polarization reversal is governed by coherent layer motion or by domain-wall motion. Recently, Professor Xiaoxiang Xi’s group at School of Physics, Nanjing University reported shear-mode Raman imaging as a device-scale structural probe of sliding ferroelectric switching in multilayer 3R-MoS₂. By exploiting the sensitivity of interlayer shear modes to layer number and stacking order, they directly tracked the electric-field-driven evolution of stacking configurations and domain structures in dual-gated devices. The measurements show that ferroelectric switching is dominated by pre-existing domain walls. Mechanically segmented regions within a single flake switch independently, follow distinct pathways, and may reach partially polarized end states depending on the number and distribution of active domain walls. The work also reveals the influence of defect pinning and superlubric domain-wall motion on switching dynamics, and identifies characteristic domain-wall and boundary orientations beyond existing models. The results are reported in Physical Review Letters, under the title “Shear-Mode Raman Imaging of Ferroelectric Switching in Multilayer 3R-MoS₂”.

Publication link: https://doi.org/10.1103/2xv1-t31x