Researchers used angle-resolved photoemission spectroscopy (ARPES) at the Advanced Light Source (ALS) to demonstrate the existence of dark—state electrons in solids for the first time, providing insights into complex phenomena in physics, such as high-temperature superconductivity and optoelectronics.
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ALS Work Using ARPES
Angle-resolved photoemission spectroscopy (ARPES) is a technique in which a highly focused beam of x-rays is used to kick electrons out of the sample. By analyzing the ejected electrons' direction and energy, the researchers can obtain the material's band structure—a map of the electrons' behavior in the material.
Not All Gaps Are Created Equal
Researchers found that charge density waves (CDWs) in topological materials induce unconventional spectral gaps in the materials’ electronic structure. The finding that CDWs in topological materials can be essentially different from that in other materials should be carefully considered when designing quantum devices. Read more »
Lattice-Dependent Spin Textures in High-Tc Superconductors
Researchers found that in bismuth-based cuprate superconductors, charge imbalances caused by lattice distortions generate persistent and universal patterns of spin polarization. The results supply a previously missing but essential ingredient in efforts to understand the mechanisms driving the electronic behavior of high-temperature superconductors. Read more »
Strategic ALS Projects Reach Key Milestones
Thanks to the hard work and dedication of multidisciplinary teams from groups across the ALS, a spate of important milestones occurred over the past month, for projects involving the new QERLIN beamline, the MERLIN beamline upgrade, and a new chamber for computer-chip metrology in Sector 12. Read more »
Stabilizing Pristine α-Sn Thin Films for Topological Investigation
Researchers developed a recipe for the room-temperature stabilization of thin films of α-Sn, a form of elemental tin that exhibits a variety of topologically nontrivial phases, but only at low temperatures. By dramatically reducing contamination from the film’s substrate, the recipe greatly simplifies electronic structure studies. Read more »
Room-Temperature 2D Magnet: Electronic-Structure Insights
Researchers found that small changes in how electron spins interact with each other can make a big difference in the magnetic transition temperatures of 2D magnets. Understanding such factors can help create better magnetic materials for information storage, sensors, medical imaging, and energy-efficient computing. Read more »
Big Twist Leads to Tunable Energy Gaps in a Bilayer Stack
Researchers found that twisting 2D layers at atypically large angles opens up potentially useful energy gaps in the material’s band structure. The results suggest a new way to tune materials for optoelectronic applications and provide a platform for exploring novel “moiré” phenomena beyond those observed at small twist angles. Read more »
Flat Bands Signal Electrons Trapped in 3D
Researchers found flat electronic band structures—known hallmarks of electrons trapped in two dimensions—but in a material that extends this phenomenon to three dimensions. The work opens up a material framework for exploring superconductivity and other exotic states in three dimensions for advanced electronic applications. Read more »
Building a Two-Dimensional Magnet One Atom at a Time
Researchers synthesized a new two-dimensional ferromagnet and measured how its electronic and magnetic properties evolve with increasing thickness and temperature. Such atomically thin magnetic materials with tunable magnetic properties would be very useful in next-generation microelectronic and spintronic applications. Read more »
Excitons Dance the Two-Step in a 2D Material
Excitonic insulators are a rare form of macroscopic quantum state that can be realized at a high temperature, which can be useful for quantum information science. At the ALS, researchers found that in a 2D material, a novel two-step “folding” behavior in the ARPES data signals the existence of an intermediate exciton gas state. Read more »
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