Catálogo de publicaciones - revistas

<jats:title>Exotic topology on the surface</jats:title> <jats:p> Analyzing the spatial symmetries of three-dimensional (3D) crystal structures has led to the discovery of exotic types of quasiparticles and topologically nontrivial materials. Wieder <jats:italic>et al.</jats:italic> focus on the symmetry groups of 2D surfaces of 3D materials—the so-called wallpaper groups—and find that some of them allow for an additional topological class. This class hosts a single fourfold-degenerate Dirac fermion on the surface of the material and, on the basis of the authors' calculations, is expected to occur in the compound Sr <jats:sub>2</jats:sub> Pb <jats:sub>3</jats:sub> . </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6399" page="246" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aan2802">246</jats:related-article> </jats:p>

<jats:title>Changing emission with charge states</jats:title> <jats:p> The fluorescence of electrochromic molecules changes with their charge state. Doppagne <jats:italic>et al.</jats:italic> studied the optical emission of single zinc-phthalocyanine molecules excited by electron injection from a scanning tunneling microscope tip. The molecules were adsorbed on salt layers grown on a gold surface, so that the cationic and neutral molecules could both be observed. The primary emission shifted to lower energy for the cation, and, in addition, vibrational side bands were observed. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6399" page="251" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aat1603">251</jats:related-article> </jats:p>

<jats:title>A balance between motion and cooperation</jats:title> <jats:p> In active matter systems, the infusion of energy and motion drives ordering processes. Huber <jats:italic>et al.</jats:italic> present a combination of experiments and numerical simulations on an active matter system consisting of actin filaments propelled across a surface by surface-attached myosin motor proteins. Adding a depletion agent—polymer chains that weakened interactions between the actin filaments—drove the system between ferromagnetic (polar) and nematic (liquid crystal) ordering. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6399" page="255" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aao5434">255</jats:related-article> </jats:p>

<jats:title>An atom-coupling cavity</jats:title> <jats:p> Ensembles of atoms have emerged as powerful simulators of many-body dynamics. Engineering controllable interactions between the atoms is crucial, be it direct or through a mediator. Norcia <jats:italic>et al.</jats:italic> developed a flexible alternative to existing atomic simulators in a system consisting of strontium atoms placed in an optical cavity. Two atomic states connected by a clock transition each served as an effective spin, with long-range spin-exchange interactions mediated by the cavity photons. With improvements, the setup is expected to be amenable to simulating nonequilibrium quantum dynamics and to have applications in metrology. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6399" page="259" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aar3102">259</jats:related-article> </jats:p>

<jats:title>Oscillating one-dimensional chains</jats:title> <jats:p> The confinement of materials to nanoscale dimensions often reveals properties not seen in bulk materials. Pham <jats:italic>et al.</jats:italic> confined NbSe <jats:sub>3</jats:sub> within carbon nanotubes (a conductor) or boron nitride nanotubes (an insulator). Transmission electron microscopy revealed an oscillatory motion of the confined chains not observed in bulk crystals. Electronic structure calculations showed that charge transfer drives the torsional wave instability, and the limited covalent bonding between the chains and the nanotube sheath allows unhindered dynamics. Application of an external potential applied to the nanotube should directly affect the torsion and thus lead to different optical and electron transport properties. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6399" page="263" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aat4749">263</jats:related-article> </jats:p>

<jats:title>Fault-tolerant quantum coding</jats:title> <jats:p> Noise and imperfections in a quantum system can result in the presence and propagation of errors through the system. A reliable quantum processor will need to be able to correct for these errors and error syndromes. Rosenblum <jats:italic>et al.</jats:italic> used higher quantum states of a superconducting-based quantum circuit to demonstrate a method for the fault-tolerant measurement of an error-correctable logical qubit. Such fault-tolerant measurements will allow more frequent interrogations of the state of the logical qubit, ultimately leading to the implementation of more quantum operations and more complex entangled quantum circuits. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6399" page="266" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aat3996">266</jats:related-article> </jats:p>

<jats:title>South Asian monsoon and pollution</jats:title> <jats:p> Air pollution is growing fastest in monsoon-impacted South Asia. During the dry winter monsoon, the fumes disperse toward the Indian Ocean, creating a vast pollution haze. The fate of these fumes during the wet summer monsoon has been unclear. Lelieveld <jats:italic>et al.</jats:italic> performed atmospheric chemistry measurements by aircraft in the Oxidation Mechanism Observations campaign, sampling the summer monsoon outflow in the upper troposphere between the Mediterranean and the Indian Ocean. The measurements, supported by model calculations, show that the monsoon sustains a remarkably efficient cleansing mechanism in which contaminants are rapidly oxidized and deposited on Earth's surface. However, some pollutants are lofted above the monsoon clouds and chemically processed in a reactive reservoir before being redistributed globally, including to the stratosphere. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6399" page="270" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aar2501">270</jats:related-article> </jats:p>