• Physics 16, s39
Two atom-thick layers of the identical crystalline materials will be stacked on prime of one another in ways in which yield ferroelectricity.
A ferroelectric crystal snaps between two reverse and secure polarizations in response to an electrical discipline. The states’ robustness and the truth that voltage—quite than a extra unwieldy magnetic discipline—performs the switching make ferroelectrics engaging for nonvolatile reminiscence and different purposes. In precept, crystalline monolayers are ideally suited ferroelectrics. Their thinness reduces each the requisite switching discipline energy and the amount that the fabric occupies in a tool. However monolayers’ lack of a 3rd dimension lessens their alternative to exhibit a vital property of ferroelectric supplies: a structural asymmetry alongside the out-of-plane axis. Now Changsong Xu and Hongjun Xiang of Fudan College in China and their collaborators have developed a mannequin that predicts how this vital asymmetry will be engineered by stacking two monolayers with misalignments between their crystal buildings .
Classifying 3D crystal buildings by their symmetries dates again to the 1830s. Within the case of 2D monolayers, the potential buildings occupy 80 mathematically outlined teams. The stacking and shifting of monolayers to kind bilayers creates and destroys symmetries. Lately, researchers proposed that the symmetry discount obtained by inserting one monolayer on prime of one other of the identical materials and shifting it will create a bilayer with ferroelectric properties. Xu, Xiang, and their colleagues present that every one the potential sorts of monolayers and all of the potential sorts of stacking (rotations and shifts) will be analyzed inside a single group principle framework. By making use of the strategies of group principle, they will determine which buildings and which stackings yield ferroelectricity. The crew’s predictions match the modest variety of stacked bilayer ferroelectrics created within the lab to date, whereas their normal principle portends the invention of many extra.
Charles Day is a Senior Editor for Physics Journal.
- J. Ji et al., “Common principle for bilayer stacking ferroelectricity,” Phys. Rev. Lett. 130, 146801 (2023).