Periodic Reporting for period 4 - STRAIN2EXTREME (Straining electromechanical coupling in layered crystals to new extremes)
Reporting period: 2024-04-01 to 2024-09-30
At the core of the electronic revolution is a tiny "transistor" device controlled rapidly and efficiently in a nearly perfect crystalline structure. Today, after decades of research and developments, it is possible to switch the response of crystals as small as 100x100x100 atoms by applying local electromagnetic fields. We use billions of millions of them in every computer, sensor, medical tool, and nearly all technology around us. Thus, efforts to better observe, understand, and control these tiny crystalline structures have an enormous impact beyond fundamental curiosity.
STRAIN2EXTREME developed new methods to manipulate the electronic response in ultimately thin layered materials by engineering the layers' stacking arrangements and structural symmetries. By assembling these artificial "van der Waals Polytypes" in the lab into metastable crystals that break the symmetry, we found that electrons jump between the layers and create internal electric polarizations that are absent in the natural crystals. We further showed that external electric fields are sufficient to slide the layers between distinct stacking configurations that revert the polarization orientation. We termed this response as "Interfacial Ferroelectricity" and pointed to numerous novel responses available by the new electric control of these structural transitions. In the following steps, we showed that this concept applies to a wide range of layered materials including graphitic polytypes, and expanded the microscopic understanding of the switching dynamics. We called it "SlideTronics" and founded a company "SlideTro LTD" that aims to bring these devices closer to practical applications.
STRAIN2EXTREME developed new methods to manipulate the electronic response in ultimately thin layered materials by engineering the layers' stacking arrangements and structural symmetries. By assembling these artificial "van der Waals Polytypes" in the lab into metastable crystals that break the symmetry, we found that electrons jump between the layers and create internal electric polarizations that are absent in the natural crystals. We further showed that external electric fields are sufficient to slide the layers between distinct stacking configurations that revert the polarization orientation. We termed this response as "Interfacial Ferroelectricity" and pointed to numerous novel responses available by the new electric control of these structural transitions. In the following steps, we showed that this concept applies to a wide range of layered materials including graphitic polytypes, and expanded the microscopic understanding of the switching dynamics. We called it "SlideTronics" and founded a company "SlideTro LTD" that aims to bring these devices closer to practical applications.
After optimizing the methods to assemble and measure these ultimately thin crystals with a mono-layer thickness resolution and minute relative twists, we detected the electric potential variations at the surface of the various polytypes. It allowed us to reveal the microscopic structural switching mechanism. The external field imposes efficient sliding motion of boundary dislocations strips between the crystalline phases (Science 2021). Later, we found that with each extra layer the electric potential accumulates in a linear fashion and that we can increase the planar conductivity while maintaining the vertical polarization (Nature 2022). Both effects are unavailable in typical 3D ferroelectric materials. We also identifies the egergy gap of the crystal as the limit of this potential accumulation (ADMAT 2024). We believe that adding more layers to cross this potential limit results is conductive surface states of charged electrons and holes at the two opposite surfaces of the crystal. Finaly, we discovered a finite room temperature polarization even in graphitic polytypes made of graphene layers and carbon atoms only (ADRP 2023). The rich family of van der Waals materials and the numerous “SlideTronic” opportunities arising by switching from one polytype to another are summarized in our recent perspective paper (Nature Review Physics 2024).
Currently, we expand the fundamental aspects of this novel structural control mechanism in a new "SlideTronics" ERC project.