Abstract：

　　The tunability of the stacking order in van der Waals materials provides a new and powerful method to engineer their physical properties. In parallel-stacked transition metal dichalcogenides, also known as the rhombohedral stacking order, the equilibrium atomic structure is asymmetric between layers, leading to a spontaneous electrical polarization across the vdW gap. Under an external electric field, the layer configuration and its associated polarization can be switched - a phenomenon recently termed as sliding ferroelectricity. We experimentally measured the polarization strength and its spatial distribution in chemically synthesized rhombohedral MoS₂. We observed that the domain size distribution follows a power-law distribution, suggesting that the shear strain occurring during the mechanical exfoliation can induce an avalanche of domain wall motion. These pre-existing domain walls were found to be crucial for the polarization switching behavior and we leveraged them to achieve a non-volatile control over the optical response of these layered semiconductors.

Personal introduction: 

　　Ziliang Ye is an assistant professor of physics and astronomy at the Quantum Matter Institute at the University of British Columbia, where he also holds the Tier II Canada Research Chair. Ziliang’s expertise is in probing two-dimensional materials using advanced optical spectroscopy techniques. Ziliang received his PhD from the University of California Berkeley in 2013 and worked as a postdoctoral fellow with Tony Heinz at Columbia and Stanford Universities before joining the faculty at UBC in 2018.