Volume 10 Issue 9, September 2014

Volume 10 Issue 9

How do flocks of birds remain cohesive while dodging predators? A study tracking up to 400 starlings reveals that information propagates in a linear fashion and with no attenuation, meaning that the language of phase transitions in correlated materials can be used to describe flocking behaviour.Article p691 IMAGE: EDWARD SHEN AND COBBS LAB, ISC-CNR, ROME COVER DESIGN: ALLEN BEATTIE

Editorials

  • Editorial |

    If Scotland votes to leave the United Kingdom, will the independent nation maintain its level of science funding?

  • Editorial |

    As the ninth year of Nature Physics draws to a close, we say goodbye to our launching Chief Editor, Alison Wright, and welcome her successor, Andrea Taroni, to the team.

Commentary

  • Commentary |

    Discoveries in astronomy — or, in fact, any branch of science — can only happen when people are open-minded and willing to take risks.

    • Abraham Loeb

Thesis

  • Thesis |

    • Mark Buchanan

Books and Arts

  • Books & Arts |

    • Andreas Trabesinger

Research Highlights

News and Views

  • News & Views |

    Detection of coherent energy transport has fuelled claims that quantum effects make photosynthesis more efficient. Experiments now show that the interplay between electronic and vibrational motion also sustains coherence in the subsequent charge-separation process.

    • Susana F. Huelga
    •  & Martin B. Plenio
  • News & Views |

    Frustration in spin systems can emerge geometrically in the absence of intrinsic energetic degeneracy — a topologically induced state that can be visualized in terms of a lattice walk. Now, evidence confirms that the exotic 'shakti' lattice gives rise to such a topology.

    • Robert L. Stamps
  • News & Views |

    Probing an unknown quantum state is a resource-intensive endeavour. Now, it is shown that it may be faster to record observations that are themselves quantum superpositions, rather than classical data.

    • Yi-Kai Liu
  • News & Views |

    A cable-like ring of biopolymers helps to pull cells together across the site of a wound. Widely thought to be homogeneous, the traction forces involved are actually remarkably heterogeneous — revealing an unexpected pattern of force generation during wound repair.

    • Miranda V. Hunter
    •  & Rodrigo Fernandez-Gonzalez
  • News & Views |

    Liquid–liquid phase separation is counted among the peculiar phenomena attributed to pure water, but rapid crystallization has rendered its existence hard to prove. Evidence of a 'naked' liquid–liquid transition in a system unencumbered by crystallization encourages us to keep searching.

    • Francis W. Starr

Letters

  • Letter |

    Characterizing an unknown quantum state typically relies on analysing the outcome of a large set of measurements. Certain quantum-processing tasks are now shown to be realizable using only approximate knowledge of the state, which can be gathered with exponentially fewer resources.

    • Seth Lloyd
    • , Masoud Mohseni
    •  & Patrick Rebentrost
  • Letter |

    High-Tc superconducting cuprates exhibit gap nodes. Recent experiments have revealed the existence of a node-free superconducting-like energy gap in deeply underdoped cuprates. Now it is argued that such systems are topological superconductors with antiferromagnetic order.

    • Yuan-Ming Lu
    • , Tao Xiang
    •  & Dung-Hai Lee
  • Letter |

    Majorana fermions, which are their own antiparticles, are expected to exist in topological superconductors. A study using superconducting leads in contact with a quantum well reveals the presence of supercurrents along one-dimensional sample edges of a quantum spin Hall state. These edge supercurrents are topological.

    • Sean Hart
    • , Hechen Ren
    • , Timo Wagner
    • , Philipp Leubner
    • , Mathias Mühlbauer
    • , Christoph Brüne
    • , Hartmut Buhmann
    • , Laurens W. Molenkamp
    •  & Amir Yacoby
  • Letter |

    In a Josephson junction, a current flows from one superconductor to another through a barrier without any voltage being applied. SQUIDs, for example, are based on this phenomenon. Now, an iron-based multi-band superconductor shows signs of intrinsic Josephson junctions, opening up prospects for applications.

    • Philip J. W. Moll
    • , Xiyu Zhu
    • , Peng Cheng
    • , Hai-Hu Wen
    •  & Bertram Batlogg
  • Letter |

    Under certain conditions electrons in confined systems can solidify into Wigner crystals. Nuclear magnetic resonance is used to probe the local electron density of a two-dimensional system in quantum Hall regimes, revealing the role of quantum and thermal fluctuations in Wigner crystallization.

    • L. Tiemann
    • , T. D. Rhone
    • , N. Shibata
    •  & K. Muraki
  • Letter |

    Fetching an object by means of sending a wave—impossible? Not necessarily. As now demonstrated experimentally, generating waves on a water surface using a set of plungers can cause a floating particle to move counter to the general direction of wave propagation. The effect originates from vorticity creation by steep 3D waves.

    • Horst Punzmann
    • , Nicolas Francois
    • , Hua Xia
    • , Gregory Falkovich
    •  & Michael Shats

Articles

  • Article |

    The conducting surface states of 3D topological insulators are two-dimensional. In an analogous way, the edge states of 2D topological insulators are one-dimensional. Direct evidence of this one-dimensionality is now presented, by means of scanning tunnelling spectroscopy, for bismuth bilayers—one of the first theoretically predicted 2D topological insulators.

    • Ilya K. Drozdov
    • , A. Alexandradinata
    • , Sangjun Jeon
    • , Stevan Nadj-Perge
    • , Huiwen Ji
    • , R. J. Cava
    • , B. Andrei Bernevig
    •  & Ali Yazdani
  • Article |

    The shakti lattice describes a new type of frustration not found in naturally occurring materials. Fabrication of the first artificial spin-ice array displaying shakti dynamics confirms the locally ordered, globally degenerate nature of these exotic lattice structures.

    • Ian Gilbert
    • , Gia-Wei Chern
    • , Sheng Zhang
    • , Liam O’Brien
    • , Bryce Fore
    • , Cristiano Nisoli
    •  & Peter Schiffer
  • Article |

    Two-dimensional electronic spectroscopic data and theoretical simulations provide the most convincing evidence so far that organisms exploit quantum coherence for efficient energy conversion during photosynthesis.

    • Elisabet Romero
    • , Ramunas Augulis
    • , Vladimir I. Novoderezhkin
    • , Marco Ferretti
    • , Jos Thieme
    • , Donatas Zigmantas
    •  & Rienk van Grondelle
  • Article |

    Wound repair is thought to involve cell migration and the contraction of a tissue-level biopolymer ring—invoking analogy with the pulling of purse strings. Traction-force measurements now show that this ring engages the tissue's surroundings to steer migration, prompting revision of the purse-string mechanism.

    • Agustí Brugués
    • , Ester Anon
    • , Vito Conte
    • , Jim H. Veldhuis
    • , Mukund Gupta
    • , Julien Colombelli
    • , José J. Muñoz
    • , G. Wayne Brodland
    • , Benoit Ladoux
    •  & Xavier Trepat
  • Article |

    How do flocks of birds remain cohesive while dodging predators? A study tracking up to 400 starlings reveals that information propagates in a linear fashion and with no attenuation, meaning that the language of phase transitions in correlated materials can be used to describe flocking behaviour.

    • Alessandro Attanasi
    • , Andrea Cavagna
    • , Lorenzo Del Castello
    • , Irene Giardina
    • , Tomas S. Grigera
    • , Asja Jelić
    • , Stefania Melillo
    • , Leonardo Parisi
    • , Oliver Pohl
    • , Edward Shen
    •  & Massimiliano Viale

Futures

Correction