קולוקוויום בפיזיקה: SlideTronics: Switching Crystalline Symmetries by Interfacial Superlubricity
Dr. Moshe Ben Shalom, TAU
The crystalline matter is defined as a tiny unit cell made of a few atoms only that repeat periodically on macroscopic scales. Its properties are determined by the particular atomic composition and the unit cell's symmetries under different geometrical transformations. Perhaps one of the most significant achievements of the past century is the accurate control of these properties in tiny crystalline structures, allowing each of us to switch their response more than a billion times every second in every technology we face.
Still, it is challenging to separately explore the impact of a unit cell's symmetry versus its atomic composition, let alone control. Quantum mechnics couple the two factors together to optimize the stability of the structure. Recently, however, we discovered a unique van der Waals (vdW) sliding mechanism that switches between meta-stable stacking configurations of identical atoms with different crystalline symmetries. By applying external electric fields or shear stress, we showed that the domain walls between crystalline polytypes could propagate in a "super-lubric" manner and switch the local meta-stable stacking and its symmetry. In particular, we could break and restore the local mirror symmetry of the structure and measure the internal charge redistribution in an ultimately two-atom-thin polar unit cell. The talk will discuss our first steps into this emerging field of "SlideTronics": our recent conclusions on the competing responses of polar charge distribution versus conductivity and of distinct ladder-like polarization steps that accumulate in a co-aligned/anti-aligned orientation with each extra atomic layer depending on the stacking symmetry.
"Interfacial ferroelectricity by van-der-Waals sliding"
"Cumulative Polarization in Conductive Interfacial Ferroelectrics"
מארגן האירוע: פרופ' רנן ברקנא (http://wise-obs.tau.ac.il/~barkana/colloq.html)