Volume 9 Issue 4, April 2013

Volume 9 Issue 4

Linking two smoke rings or tying a single ring into a knot is no easy feat. Now, however, such topological vortices are created in water using 3D-printed hydrofoils. High-speed imaging shows how the linked rings spontaneously separate, and the knots are able to free themselves. Similar fluid dynamics may also be relevant in plasmas, quantum fluids and optics. Article p253; News & Views p207 IMAGE: DUSTIN KLECKNER AND WILLIAM IRVINE COVER DESIGN: ALLEN BEATTIE

Editorial

  • Editorial |

    Millions of dollars of prize money are up for grabs in fundamental physics, through an entrepreneur-funded scheme that should complement, rather than challenge, the Nobel awards.

Commentary

  • Commentary |

    A class of two-terminal passive circuit elements that can also act as memories could be the building blocks of a form of massively parallel computation known as memcomputing.

    • Massimiliano Di Ventra
    •  & Yuriy V. Pershin

Thesis

Research Highlights

News and Views

  • News & Views |

    A reworking of the theory of particle interactions — the same theory but rendered in a new form based on twistor geometry — is likely to have wide implications for physics, including the reformulation of gravity.

    • Andrew Hodges
  • News & Views |

    Linking two smoke rings or tying a single ring into a knot is no easy feat. Such topological vortices are now created in water with the aid of specially printed hydrofoils.

    • Daniel P. Lathrop
    •  & Barbara Brawn-Cinani
  • News & Views |

    Recently developed experimental and theoretical tools uncover the complex and unexpected behaviour of impurities propagating through an ensemble of ultracold atoms.

    • Patrick Windpassinger
  • News & Views |

    A snapshot of electrons crossing a metal/organic interface provides a better understanding of spin filtering and hints at new directions for designing spintronic devices.

    • Valentin Alek Dediu
  • News & Views |

    Introducing connections between two distinct networks can tip the balance of power — at times enhancing the weaker system. The properties of the nodes that are linked together often determine which network claims the competitive advantage.

    • Raissa M. D'Souza

Letters

  • Letter |

    When CaFe2As2 is lightly doped with Co an electronic liquid-crystalline state emerges, which becomes the ‘parent’ state of high-temperature superconductivity in this ferropnictide. A spectroscopic imaging study shows that the ‘nematic’ order is likely to be an artefact of the doping itself.

    • M. P. Allan
    • , T-M. Chuang
    • , F. Massee
    • , Yang Xie
    • , Ni Ni
    • , S. L. Bud’ko
    • , G. S. Boebinger
    • , Q. Wang
    • , D. S. Dessau
    • , P. C. Canfield
    • , M. S. Golden
    •  & J. C. Davis
  • Letter |

    Electrons can travel though very pure materials without scattering from defects. In this ballistic regime, magnetic fields can manipulate the electron trajectory. Such magnetic electron focusing is now observed in graphene. Although the effect has previously been seen in metals and semiconductors, it is evident in graphene at much higher temperatures—including room temperature.

    • Thiti Taychatanapat
    • , Kenji Watanabe
    • , Takashi Taniguchi
    •  & Pablo Jarillo-Herrero
  • Letter |

    Networks competing for limited resources are often more vulnerable than isolated systems, but competition can also prove beneficial—and even prevent network failure in some cases. A new study identifies how best to link networks to capitalize on competition.

    • J. Aguirre
    • , D. Papo
    •  & J. M. Buldú

Articles

  • Article |

    Understanding the propagation of spin excitations is a difficult problem in quantum magnetism. Using site-resolved imaging in a one-dimensional atomic gas, it is possible to track the dynamics of a moving spin impurity through the Mott-insulator and superfluid regimes.

    • Takeshi Fukuhara
    • , Adrian Kantian
    • , Manuel Endres
    • , Marc Cheneau
    • , Peter Schauß
    • , Sebastian Hild
    • , David Bellem
    • , Ulrich Schollwöck
    • , Thierry Giamarchi
    • , Christian Gross
    • , Immanuel Bloch
    •  & Stefan Kuhr
  • Article |

    Understanding the origin of spin filtering in metal/organic interfaces is important for the control of spin injection in organic semiconductors. A time-resolved photoemission experiment shows that spin filtering can be explained by the trapping of electrons in spin-dependent potentials at the interface.

    • Sabine Steil
    • , Nicolas Großmann
    • , Martin Laux
    • , Andreas Ruffing
    • , Daniel Steil
    • , Martin Wiesenmayer
    • , Stefan Mathias
    • , Oliver L. A. Monti
    • , Mirko Cinchetti
    •  & Martin Aeschlimann
  • Article |

    The efficiency of carrier–carrier scattering in graphene is now experimentally demonstrated. The dominance of this mechanism over phonon-related scattering means that a single high-energy photon could create two or more electron–hole pairs in graphene; an effect useful for optoelectronic applications.

    • K. J. Tielrooij
    • , J. C. W. Song
    • , S. A. Jensen
    • , A. Centeno
    • , A. Pesquera
    • , A. Zurutuza Elorza
    • , M. Bonn
    • , L. S. Levitov
    •  & F. H. L. Koppens
  • Article |

    Linking two smoke rings or tying a single ring into a knot is no easy feat. Now, however, such topological vortices are created in water using 3D-printed hydrofoils. High-speed imaging shows how the linked rings spontaneously separate, and the knots are able to free themselves. Similar fluid dynamics may also be relevant in plasmas, quantum fluids and optics.

    • Dustin Kleckner
    •  & William T. M. Irvine