Sliding vdW Polytypes

Electric field control of structural transitions is typically impractical due to the large energy re-quired for breaking solid bonds. Recently, however, structural switching between different lattice orientations of layered materials was demonstrated owing to relatively weak van der Waals (vdW) attraction between successive layers. In response to external electric fields, the layers slide along vdW interfaces to switch between meta-stable configurations with distinct properties. These so-called 2D vdW polytypes exhibit substantial interlayer band hybridizations and diverse electronic, optical, and magnetic responses that switch via super-lubricant sliding of incommensurate boundary strips.<br/>The talk outlines the many possible vdW polytypes in mono and binary compounds, their typical stacking energies, orbital inter-layer overlaps, and discrete symmetries. The distinct response of each polytype, its internal charge redistribution, electric polarization, and underlying band structure are further discussed with emphasis on our recent reports of interfacial ferroelectricity [1], ladder-like cumulative polarization [2,3], doping-dependent polarization in elemental graphitic polytypes [4], and the microscopic switching dynamics between polytypes. Lastly, I will describe our efforts to extend this conceptual "Slide-Tronics" switching mechanism to practical devices.<br/><br/>[1] "Interfacial ferroelectricity by van-der-Waals sliding"<br/>https://www.science.org/doi/10.1126/science.abe8177<br/>[2] "Cumulative Polarization in Conductive Interfacial Ferroelectrics"<br/>https://www.nature.com/articles/s41586-022-05341-5<br/>[3] “Polarization Saturation in Multilayered Interfacial Ferroelectrics”<br/>https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202400750<br/>[4] "Spontaneous Electric Polarization in Graphene Polytypes"<br/>https://onlinelibrary.wiley.com/doi/full/10.1002/apxr.202300095