(Funded by the U.S. Department of Energy)
Scientists from the Massachusetts Institute of Technology, Arizona State University, the U.S. Department of Energy’s Brookhaven National Laboratory, Sorbonne University in Paris, France, and Utrecht University in the Netherlands have reported new insights into exotic particles that are key to a form of magnetism that originates from ultrathin materials only a few atomic layers thick. The scientists identified the microscopic origin of these particles, known as excitons, and showed how they can be controlled by chemically “tuning” the material, which is primarily composed of nickel. Also, the scientists found that the excitons propagate throughout the bulk material instead of being bound to the nickel atoms.

(Funded by the National Science Foundation and the U.S. Department of Energy)
Researchers from Florida State University, the University of California Santa Barbara, Tsinghua University in China, Leipzig University in Germany, and Stuttgart University in Germany have identified, for the first time, the existence of local collective excitations of #electrons, called #plasmons, in a #Kagome metal – a class of materials whose atomic structure follows a hexagonal pattern that looks like a traditional Japanese basket weave – and found that the wavelength of those plasmons depends upon the thickness of the metal. The researchers also found that changing the frequency of a #laser shining at the metal caused the plasmons to spread through the material rather than staying confined to the surface. “[O]ur research reveals how electron interactions can create these unique waves at the nanoscale,” said Guangxin Ni, the scientist who led this study. “This breakthrough is key for advancing technologies in nano-optics and nano-photonics.”

(Funded by the National Science Foundation and the U.S. Department of Energy)
Researchers from Penn State and the National Institute for Materials Science in Japan have created a switch that turns on and off the presence of “kink states” – electrical conduction pathways at the edge of semiconducting materials. By controlling the formation of the kink states, researchers can regulate the flow of electrons in a quantum system. Kink states exist in a quantum device built with a bilayer graphene, which comprises two layers of atomically thin carbon stacked together, in such a way that the atoms in one layer are misaligned to the atoms in the other. “The amazing thing about our devices is that we can make electrons moving in opposite directions not collide with one another … even though they share the same pathways,” said Ke Huang, one of the scientists involved in this study.

(Funded by the U.S. Department of Energy)
Researchers from the U.S. Department of Energy’s National Renewable Energy Laboratory have developed a trilayer of semiconductors to enable the dissociation of electron-hole pairs, also called excitons – a fundamental process for the performance of photovoltaic systems. The trilayer, which consists of single-walled carbon nanotubes sandwiched between two semiconductors, enables a photo-induced charge transfer cascade, in which electrons move in one direction, while holes move in the other direction. The trilayer architecture appears to facilitate ultrafast hole transfer and exciton dissociation, resulting in a long-lived charge separation.

(Funded by the U.S. Department of Energy, the National Science Foundation, and the National Aeronautics and Space Administration)
For the first time, researchers from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), Dartmouth College, Penn State, the University of California, Merced, and Université Catholique de Louvain in Belgium have demonstrated an approach that combines high-throughput computation and atomic-scale fabrication to engineer high-performance quantum defects. The researchers developed state-of-the-art, high-throughput computational methods to screen and accurately predict the properties of more than 750 defects in a two-dimensional material called tungsten disulfide. Then, working at the Molecular Foundry, a user facility at Berkeley Lab, the researchers developed and applied a technique that enables the creation of vacancies in tungsten disulfide and the insertion of cobalt atoms into these vacancies.