(Funded by the U.S. Department of Energy)
Researchers from Penn State; Columbia University; the National Renewable Energy Laboratory in Golden, CO; TUD Dresden University of Technology in Germany; King’s College London; Radboud University in the Netherlands; the University of Chemistry and Technology Prague in the Czech Republic; and the University of Regensburg in Germany have identified a surface exciton – an excited electron and the hole it leaves behind – in chromium sulfide bromide, a layered magnetic semiconductor. Cooling chromium sulfide bromide down to around –223 degrees Fahrenheit brings it to a ground state, or the state of lowest energy. This transforms it into an antiferromagnetic system, in which the magnetic moments – referred to as “spin” – of the system’s particles align in a regular, repeating pattern. This antiferromagnetic ordering ensures that each layer alternates its magnetic alignment. As a result, excitons tend to stay in the layer with the same spin. Like cars on alternating one-way streets, these established boundaries keep excitons confined to the layer with which they share the same spin directions.

(Funded by the U.S. Department of Energy and the U.S. National Science Foundation)
Researchers from the U.S. Department of Energy’s SLAC National Accelerator Laboratory; Villanova University; Northwest Missouri State University; Deutsches Elektronen-Synchrotron DESY in Hamburg, Germany; the Max Planck Institute of Quantum Optics in Garching, Germany; the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany; the Institute for Photonics and Nanotechnologies in Milano, Italy; and Politecnico di Milano in Italy have observed how electrons, excited by ultrafast light pulses, danced in unison around fullerene (C60) molecules. Researchers measured this dance with unprecedented precision, achieving the first measurement of its kind at the sub-nanometer scale. The synchronized dance of electrons, known as plasmonic resonance, can confine light for brief periods of time. While they’ve been studied extensively in systems from several centimeters across to those just 10 nanometers wide, this is the first time researchers were able to break the field’s “nanometer barrier.”

Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have unveiled a new technique that could help advance the development of quantum technology. Their innovation provides an unprecedented look at how quantum materials behave at interfaces. “This technique allows us to study surface phonons — the collective vibrations of atoms at a material’s surface or interface between materials,” said Zhaodong Chu, one of the scientists involved in this study. ​“Our findings reveal striking differences between surface phonons and those in the bulk material, opening new avenues for research and applications.” Some of the research activities were performed at Argonne’s Center for Nanoscale Materials, a DOE Office of Science user facility.

(Funded by the U.S. Department of Energy)
Researchers from Rice University; the Massachusetts Institute of Technology; Carnegie Mellon University; the National University of Singapore; Southern University of Science and Technology in Shenzhen, China; and Osaka University in Japan have found a two-dimensional (2D) carbon material that is tougher than graphene and resists cracking. Carbon-derived materials, such as graphene, are among the strongest on Earth, but once established, cracks propagate rapidly through them, making them prone to sudden fracture. The new carbon material, called a monolayer amorphous carbon, is both strong and tough. Like graphene, this material is also a 2D material, but unlike graphene, in which atoms are arranged in an ordered lattice, this material incorporates both crystalline and amorphous regions. “This unique design prevents cracks from propagating easily, allowing the material to absorb more energy before breaking,” said Bongki Shin, one of the researchers involved in this study.

(Funded by the U.S. Department of Energy)
Scientists from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, SLAC National Accelerator Laboratory, and Lawrence Berkeley National Laboratory; the University of California, Berkeley; Pennsylvania State University; Stanford University; Rice University; the Indian Institute of Science in Bangalore, India; the Japan Synchrotron Radiation Research Institute in Sayo, Japan; RIKEN SPring-8 Center in Sayo, Japan; and the University of Tokyo in Japan are investigating a material with a highly unusual structure – one that changes dramatically when exposed to an ultrafast pulse of light from a laser. At the Center for Nanoscale Materials, a DOE Office of Science user facility at Argonne, the scientists used a technique called transient absorption spectroscopy to detect photocarrier activity within the material. This approach helped them determine how much charge gets released and how quickly the charge decays.