Materials development is the foundation for many technology innovations. Often, when one material is integrated with another, new properties and functionalities can emerge. That’s the case with 2D quantum materials or sheets of material just one atom thick. When certain materials are engineered to these dimensions, they can display enhanced electrical, magnetic and quantum properties.
Even more exciting, when these materials are layered on top of one another, they can take on surprising and useful properties such as ferroelectricity, or the capacity of certain materials to reverse polarity when exposed to an external electric field. However, the interplay of ferroelectricity and other quantum properties is a significant yet underexplored topic because most current 2D quantum materials are nonpolar.
Jun Xiao, an assistant professor of materials science and engineering at the University of Wisconsin-Madison, will use a National Science Foundation CAREER Award to overcome this obstacle. Recent discoveries, including his previous work, indicate it is possible to design ferroelectrics out of the vast majority of 2D materials with parent nonpolar compounds by certain layer stacking engineering. The resulting ferroelectricity can be switched via interlayer sliding.
To achieve this, Xiao will implement rational design and precise stacking engineering of nonpolar magnetic monolayers into polar stacking sequences. Xiao and his students are using an in-house automatic exfoliation and transfer station that can efficiently exfoliate the 1-atom-thick layers and stack the materials on top of one another at precise angles. “This precise stacking engineering approach will unlock the exciting interplay of sliding ferroelectricity, magnetism and strong electron correlation that was previously inaccessible,” says Xiao.
To fully understand the new quantum orderings and coupling physics, Xiao and his students have developed an in-house multimodal optical, electrical and magnetic characterization platform. It will enable simultaneous access to ferroelectricity, magnetism and electron correlation at various spatial, temporal and energy scales. “With this multimodal characterization system, with one shot, we can unlock all the information simultaneously,” says Xiao.
These advances will allow the researchers to create and characterize these new layered 2D structures much more quickly and efficiently, hopefully accelerating discovery of new ways of controlling their quantum states. Xiao expects the research will benefit society by enabling energy-efficient and high-speed memory and logic devices as well as compact and programmable quantum simulators to address growing information and energy demands.
For the outreach element of his CAREER Award, Xiao is collaborating with the UW-Madison Materials Research Science and Engineering Center to develop an enrichment program called “2D ferroelectrics for energy-efficient future.” The program includes modules to reach undergraduates at non-research colleges and universities, as well as high school teachers, to introduce them to 2D and ferroelectric materials and their potential uses in information processing and energy harvesting. The team will also participate in on-campus outreach events, such as the annual UW-Madison Engineering Expo, to get K-12 students interested in nanoscale information devices.
Featured image caption: Jun Xiao, an assistant professor of materials science and engineering, working in his lab. Credit: Joel Hallberg.