Volume 10 Issue 7, July 2014

Volume 10 Issue 7

A cosmological model treating dark matter as a coherent quantum wave agrees well with conventional dark-matter theory on an astronomical scale. But on smaller scales, the quantum nature of wave-like dark matter can explain dark-matter cores that are observed in dwarf galaxies, which standard theory cannot.Letter p496; News & Views p477 IMAGE: HSI-YU SCHIVE COVER DESIGN: ALLEN BEATTIE

Editorials

  • Editorial |

    Helium has become a precious resource and its supply must be managed with care.

  • Editorial |

    Datasets can now be published, shared — and cited — in Scientific Data.

Commentaries

  • Commentary |

    Iranian scientists are growing increasingly isolated because of political tensions between Iran and the West. We attempt to alleviate this problem through science diplomacy.

    • Warren E. Pickett
    • , Anthony J. Leggett
    •  & Paul C. W. Chu

Thesis

Research Highlights

News and Views

  • News & Views |

    The ALPHA collaboration has provided the clearest evidence yet that antihydrogen is charge neutral. Attention now turns to research that could replace a universe dominated by dark matter and dark energy with one containing both matter and antimatter.

    • Thomas J. Phillips
  • News & Views |

    A surface made from an array of widely spaced tapered posts enables water drops that hit it to bounce off with a pancake-like shape. This finding provides new strategies for reducing the contact time of drops impacting on surfaces.

    • Doris Vollmer
    •  & Hans-Jürgen Butt
  • News & Views |

    Determining the sequence of events following photon absorption by a molecule can be a surprisingly challenging task. An innovative use of time-resolved X-ray spectroscopy has revealed an important insight into the ultrafast excited-state dynamics of a well-known inorganic chromophore.

    • James K. McCusker
  • News & Views |

    Despite the many successes of the cold dark matter cosmological model, observational challenges on subgalactic scales motivate researchers to consider alternatives, including a model in which dark matter is a quantum wave with an astronomically large wavelength.

    • Lawrence M. Widrow
  • News & Views |

    Quantum cryptographic schemes ensure security by sacrificing data to detect tampering. Now, an approach shows that monitoring disturbance is not essential because the limit on leaked information can be known in advance.

    • Marcos Curty
  • News & Views |

    Because of near-instant screening, photoexcited electron–hole pairs in metals are hard to investigate experimentally. Femtosecond spectroscopy is now shown to be a viable tool for studying them — and reveals the existence of 'transient excitons'.

    • Thomas Miller
  • News & Views |

    The X-ray light curve of the debris from a star torn apart by a supermassive black hole provides the best evidence yet for two such black holes orbiting close to each other.

    • Martin Gaskell

Review

  • Review Article |

    The superconducting energy gap is perhaps the best-known of the spectral gaps in a superconductor, but there are many other types, including density waves and the mysterious pseudogap. This Review Article surveys what angle-resolved photoemission spectroscopy has revealed about the various gaps.

    • Makoto Hashimoto
    • , Inna M. Vishik
    • , Rui-Hua He
    • , Thomas P. Devereaux
    •  & Zhi-Xun Shen

Letters

  • Letter |

    A cosmological model treating dark matter as a coherent quantum wave agrees well with conventional dark-matter theory on an astronomical scale. But on smaller scales, the quantum nature of wave-like dark matter can explain dark-matter cores that are observed in dwarf galaxies, which standard theory cannot.

    • Hsi-Yu Schive
    • , Tzihong Chiueh
    •  & Tom Broadhurst

    Nature Outlook:

  • Letter |

    Feshbach resonances provide a powerful tool for engineering interactions in ultracold atomic gases. The strong exciton–photon coupling in semiconductor microcavities facilitates the demonstration of a polaritonic Feshbach resonance with promising implications for manipulating polariton quantum fluids.

    • N. Takemura
    • , S. Trebaol
    • , M. Wouters
    • , M. T. Portella-Oberli
    •  & B. Deveaud
  • Letter |

    Excitons — electron–hole pairs held together by the Coulomb force — are quasiparticles that are created when light interacts with matter. In metals, exciton generation is hard to detect; indeed, holes are usually not associated with metals. Now, using femtosecond laser pulses triggering three-photon photoemission processes, excitonic response is reported for silver surfaces.

    • Xuefeng Cui
    • , Cong Wang
    • , Adam Argondizzo
    • , Sean Garrett-Roe
    • , Branko Gumhalter
    •  & Hrvoje Petek
  • Letter |

    Developing a theory that describes rotating turbulence has so far proved challenging. Now, experiments show signatures of inertial waves in rotating turbulence, implying that such flow can be thought of as resulting from interacting inertial waves—solutions of the linearized rotating Navier–Stokes equation.

    • Ehud Yarom
    •  & Eran Sharon
  • Letter |

    When a water drop bounces back from a hydrophobic surface, its initial, spherical shape is usually restored. Now, experiments with a specially engineered superhydrophobic surface made from micrometre-sized tapered pillars covered with copper oxide ‘nanoflowers’ show that droplets can bounce back with a flat, pancake-like shape.

    • Yahua Liu
    • , Lisa Moevius
    • , Xinpeng Xu
    • , Tiezheng Qian
    • , Julia M. Yeomans
    •  & Zuankai Wang
  • Letter |

    The origin of the large magnetic fields observed in the interior of the supernova remnant Cassiopeia A is still unclear. Laboratory experiments of laser-produced shocks provide new insights into the mechanisms of magnetic field amplification.

    • J. Meinecke
    • , H. W. Doyle
    • , F. Miniati
    • , A. R. Bell
    • , R. Bingham
    • , R. Crowston
    • , R. P. Drake
    • , M. Fatenejad
    • , M. Koenig
    • , Y. Kuramitsu
    • , C. C. Kuranz
    • , D. Q. Lamb
    • , D. Lee
    • , M. J. MacDonald
    • , C. D. Murphy
    • , H-S. Park
    • , A. Pelka
    • , A. Ravasio
    • , Y. Sakawa
    • , A. A. Schekochihin
    • , A. Scopatz
    • , P. Tzeferacos
    • , W. C. Wan
    • , N. C. Woolsey
    • , R. Yurchak
    • , B. Reville
    •  & G. Gregori

Articles

  • Article |

    Graphene on boron nitride gives rise to a moiré superlattice displaying the Hofstadter butterfly: a fractal dependence of energy bands on external magnetic fields. Now, by means of capacitance spectroscopy, further aspects of this system are revealed—most notably, suppression of quantum Hall antiferromagnetism at particular commensurate magnetic fluxes.

    • G. L. Yu
    • , R. V. Gorbachev
    • , J. S. Tu
    • , A. V. Kretinin
    • , Y. Cao
    • , R. Jalil
    • , F. Withers
    • , L. A. Ponomarenko
    • , B. A. Piot
    • , M. Potemski
    • , D. C. Elias
    • , X. Chen
    • , K. Watanabe
    • , T. Taniguchi
    • , I. V. Grigorieva
    • , K. S. Novoselov
    • , V. I. Fal’ko
    • , A. K. Geim
    •  & A. Mishchenko
  • Article |

    Frequency changes in the partial tones of a sound can affect the way we perceive it, a phenomenon generally understood to be cortical in origin. A mesoscopic model now attributes perceived pitch to a physical mechanism linked to the presence of the cochlear fluid.

    • Florian Gomez
    •  & Ruedi Stoop

Futures