Electronics, computing, and information technology

Researchers at the University of Illinois Urbana-Champaign, Seoul National University in South Korea, and the National Institute for Materials Science in Tsukuba, Japan, have developed a method to visualize the thermally induced rearrangement of two-dimensional (2D) materials, atom-by-atom, from twisted to aligned structures, using transmission electron microscopy. The researchers observed a new and unexpected mechanism for this rearrangement process. "People usually think of the two layers like having two sheets of paper twisted 45° to each other.

Researchers from the University of Wyoming, Pennsylvania State University, Northeastern University, the University of Texas at Austin, Colorado State University, and the National Institute for Materials Science in Tsukuba, Japan, have created an innovative method to control tiny magnetic states within ultrathin, two-dimensional (2D) van der Waals magnets – a process akin to how flipping a light switch controls a bulb.

Researchers led by Cornell University have discovered an unusual phenomenon in Mott insulators, a metal-insulating material, providing valuable insights for the design of materials with new properties by way of faster switching between states of matter. Mott insulators are not fully understood, partly due to the challenging task of imaging the material's nanostructures in real space and capturing how these nanostructures undergo phase changes in as fast as a trillionth of a second. 

Researchers from the U.S. Naval Research Laboratory and Kansas State University have discovered slab waveguides based on the two-dimensional material hexagonal boron nitride. "We knew using hexagonal boron nitride would lead to outstanding optical properties in our samples; none of us expected that it would also act as a waveguide," said Samuel Lagasse, one of the scientists involved in the study. The slabs of hexagonal boron nitride were carefully tuned in thickness so that the emitted light would be trapped within the hexagonal boron nitride and waveguided.

Physicists from the Massachusetts Institute of Technology have found that when five sheets of graphene are stacked like steps on a staircase, the resulting structure provides the right conditions for electrons to pass through as fractions of their total charge, with no need for any external magnetic field. The results are the first evidence of the "fractional quantum anomalous Hall effect" (the term "anomalous" refers to the absence of a magnetic field) in crystalline graphene, a material that physicists did not expect to exhibit this effect.

An international team of researchers from Princeton University, the University of Texas at Dallas, the National High Magnetic Field Laboratory in Tallahassee, FL, the Beijing Institute of Technology, and the University of Zurich in Switzerland has observed long-range quantum coherence effects in a topological insulator-based device, which may enable the development of efficient topological electronic devices.

Researchers at the Massachusetts Institute of Technology (MIT), using facilities at MIT and Harvard University’s Center for Nanoscale Systems (part of the National Nanotechnology Coordinated Infrastructure network), have demonstrated current-controlled, non-volatile magnetization switching in an atomically thin van der Waals magnetic material at room temperature. Magnets composed of atomically thin van der Waals materials can typically only be controlled at extremely cold temperatures, so the fact that the researchers were able to control these materials at room temperature is key.

Researchers from North Carolina State University, Arizona State University, Jeonbuk National University in South Korea, and Sungkyunkwan University in South Korea have discovered that liquid metal composites can spontaneously grow over four times in volume when exposed to water, while retaining metallic conductivity similar to their starting material. This growth occurs because water infiltration promotes oxidation reactions that generate porous gallium oxyhydroxide while freeing hydrogen gas.

Researchers from the U.S. Department of Energy's Argonne National Laboratory and Oak Ridge National Laboratory and Pusan National University in Busan, South Korea, have examined the changes that occur in the structure of a specific nanomaterial as it changes from conducting an electrical current to not. The material, strontium cobalt oxide, easily switches between conducting and insulating phases. The researchers used a technique, called X-ray photon correlation spectroscopy, that can directly measure how fast the material fluctuates between these two phases at the atomic scale.

By wrapping a carbon nanotube with a ribbon-like polymer, researchers from Duke University, the University of Pittsburgh, and the University of North Carolina, Chapel Hill, were able to create nanotubes that conduct electricity when struck with low-energy light. The approach takes a metallic nanotube, which always lets current through, and transforms it into a semiconducting form that can be switched on and off.