(Funded by the U.S. Department of Energy)
Stacking single layers of sub-nanometer-thick semiconductor materials, known as transition metal dichalcogenides, can generate a moiré potential – a “seascape” of potential energy with regularly repeating peaks and valleys. These peaks and valleys were previously thought to be stationary, but now, researchers from the Molecular Foundry, a user facility at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, and the University of California, Berkeley, along with international collaborators, have shown that the moiré potentials that emerge when transition metal dichalcogenides are stacked are constantly moving, even at low temperatures. Their discovery contributes to foundational knowledge in materials science and holds promise for advancing the stability of quantum technologies, because controlling moiré potentials could help mitigate decoherence in qubits and sensors. (Decoherence occurs when interference causes the quantum state and its information to be lost.)

(Funded by the U.S. National Science Foundation and the U.S. Department of Energy)
Scientists from the U.S. Department of Energy’s (DOE) Argonne National Laboratory (ANL) and SLAC National Accelerator Laboratory; the University of Chicago; the University of Vermont; Middlebury College; Brown University; Stanford University; and Northwestern University have observed that when semiconductor nanocrystals called quantum dots were exposed to short bursts of light, the symmetry of the crystal structure changed from a disordered state to a more organized one. The return of symmetry directly affected the electronic properties of the quantum dots by causing a decrease in the bandgap energy, which is the difference in energy that electrons need to jump from one state to another within a semiconductor material. This change can influence how well quantum dots conduct electricity and respond to electric fields. Part of this work was conducted at the Center for Nanoscale Materials, a DOE Office of Science user facility at ANL.

(Funded by the U.S. Department of Defense, the U.S. Department of Energy and the U.S. National Science Foundation)
Researchers at Caltech have developed an on-chip transducer that converts microwave photons to optical photons. The device involves a tiny silicon beam that vibrates at 5 gigahertz and couples to a microwave resonator – essentially a nanoscale box in which photons bounce around, also at 5 GHz. Using a technique called electrostatic actuation, a microwave photon is converted within that box to a mechanical vibration of the beam, and that mechanical oscillation, with the help of laser light, gets converted by the resonator into an optical photon. Such a conversion could enable the construction of large-scale distributed superconducting quantum computers.

(Funded by the U.S. Department of Energy and the National Institutes of Health)
Researchers at Cornell University have, for the first time, identified what happens when bacteria receive electrons from quantum dots. Using fluorescence lifetime imaging microscopy with two-photon excitation on a quantum dot and bacteria, the researchers identified a distinct halo surrounding the bacteria, which suggested the charge transfer was receiving some peripheral assistance. It turned out that an electron could either move directly from the quantum dot to the bacterium or be transferred from the bacterium via shuttle molecules. Photosynthetic biohybrids of this sort could potentially convert carbon dioxide into value-added chemical products, such as bioplastics and biofuels, and control other microbial processes.

(Funded by the U.S. Department of Defense and the U.S. Department of Energy)
Researchers from the Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab); the University of California, Berkeley; and Northwestern University have developed a way to engineer pseudo-bonds in materials. Instead of forming chemical bonds – which is what makes epoxies and other composites tough – the chains of molecules entangle in a way that is fully reversible. The researchers attached polystyrene chains to 100-nanometers-diameter silica particles to create “hairy particles.” These hairy particles self-assembled into a crystal-like structure, and the space available to each polystyrene chain depended on its position in the structure. While some chains became rigid under confinement, others ultimately disentangled and stretched. The result was a strong, tough, thin-film material, held firmly together by pseudo bonds of tangled polystyrene chains. The research was conducted, in part, at the Molecular Foundry, a DOE Office of Science user facility at Berkeley Lab.