Discrete and local responses of crystalline matter structures serve as pivotal elements facilitating the ongoing information revolution. A direct way to switch the properties and response of a given structure is to modify its crystalline symmetries by changing the relative atomic positions. Structural rearrangements, however, are challenging due to the solid interatomic bonds involved, which limits current technologies to alternating electronic orders without moving the atoms.
Interestingly, recent experiments suggest efficient control of atomic scale shifts in layered 2D crystals along their van der Waals (vdW) interfaces. The layers exhibit discrete sliding steps between meta-stable crystalline configurations in response to external electric fields or stress. These 2D vdW polytypes include periodic configurations that preserve substantial interlayer band hybridizations with distinct structural symmetries and diverse electronic/optical/magnetic properties. Their local switching occurs via mobile incommensurate partial dislocations lines, free to slide in a super-lubricant manner to replace one polytype with another.
The talk will outline the many possible polytypes in mono and binary compounds, their typical stacking energies, orbital inter-layer overlaps, and discrete symmetries. Following that, I will discuss the corresponding response of each polytype, including its internal charge redistribution, electric polarization, and underlying band structure. I will emphasize our recent reports of interfacial ferroelectricity [1], ladder-like cumulative polarization [2], doping-dependent polarization in elemental graphitic polytypes [3], and the microscopic details of dislocation boundary lines' dynamics between polytypes. Finally, we will discuss opportunities to extend this conceptual "slide-tronics" switching mechanism to efficient swapping between structural symmetries and orientations that should turn Sliding vdW Polytypes into a vast field of research.
[1] "Interfacial ferroelectricity by van-der-Waals sliding"
https://www.science.org/doi/10.1126/science.abe8177
[2] "Cumulative Polarization in Conductive Interfacial Ferroelectrics"
https://www.nature.com/articles/s41586-022-05341-5
[3] "Spontaneous Electric Polarization in Graphene Polytypes"