Volume 7 Issue 1, January 2011

Volume 7 Issue 1

An array of nanomagnets in a kagome lattice structure should support the creation and separation of oppositely charged monopoles, which are connected by Dirac strings of flipped dipoles. And indeed, such monopoles and their Dirac strings have now been observed at room temperature. (This image shows a related sevenring kagome spin-ice structure, with colours representing magneticmoment orientations.) Article p68 Cover design by David Shand

Editorial

  • Editorial |

    Around the world, in developed and developing countries, there is reluctance to commit to the alleviation of climate change. But investment in clean energy is growing.

Commentary

  • Commentary |

    The search for the Higgs boson could soon prove successful. Although the particle bears the name of a single physicist, many more were involved in devising the theory behind it — so which of them should share a potential Nobel Prize?

    • Luis Álvarez-Gaumé
    •  & John Ellis

Thesis

Research Highlights

News and Views

  • News & Views |

    Artificial magnetic materials may lead to studies of the thermodynamics of arbitrarily designed lattices. Unfortunately, none of the proposed materials has achieved its ground state through thermodynamic equilibrium as real materials do — until now.

    • John Cumings
  • News & Views |

    Topological insulators have a conducting surface on which spin currents are not easily scattered, although the addition of magnetic impurities does affect electronic behaviour. But is this situation unique? Graphene comes to mind.

    • Eli Rotenberg
  • News & Views |

    In the pseudogap phase of a high-temperature cuprate superconductor, conflicting evidence from different experiments points to a competing state or a precursor-to-superconductivity state. One single experiment now determines that both states exist.

    • Dirk van der Marel
  • News & Views |

    Increasing the power of ultra-high-intensity lasers requires crystal amplifiers and metre-scale optical compression gratings that are ever more difficult to build. Simulations suggest that Raman amplification in a plasma could permit the generation of laser intensities many orders of magnitude higher than currently possible.

    • Szymon Suckewer

Letters

  • Letter |

    Quantum information is often thought of in terms of manipulating discrete qubits. But continuous variables can also carry data. A method for storing continuous-variable states of light for up to a millisecond in room-temperature memories is now demonstrated.

    • K. Jensen
    • , W. Wasilewski
    • , H. Krauter
    • , T. Fernholz
    • , B. M. Nielsen
    • , M. Owari
    • , M. B. Plenio
    • , A. Serafini
    • , M. M. Wolf
    •  & E. S. Polzik
  • Letter |

    The absorption of one photon of an entangled pair by a lone trapped atom is identified by a correlation between the atomic absorption process and the detection of the second photon.

    • N. Piro
    • , F. Rohde
    • , C. Schuck
    • , M. Almendros
    • , J. Huwer
    • , J. Ghosh
    • , A. Haase
    • , M. Hennrich
    • , F. Dubin
    •  & J. Eschner
  • Letter |

    The pseudogap state in the cuprate superconductors shows signs of electronic pair formation above the superconducting temperature. Is it just a ‘precursor’ state or a separate (and competing) state? In fact, both interpretations seem to be correct.

    • Takeshi Kondo
    • , Yoichiro Hamaya
    • , Ari D. Palczewski
    • , Tsunehiro Takeuchi
    • , J. S. Wen
    • , Z. J. Xu
    • , Genda Gu
    • , Jörg Schmalian
    •  & Adam Kaminski
  • Letter |

    In magnetic nanostructures, the core of a vortex points either up or down, and the polarity can be reversed by alternating-field pulses. An experiment now demonstrates deterministic and coherent control of vortex-core polarity using sequences of resonant microwave pulses and highlights routes to optimizing the technique, which might find application in magnetic-storage devices.

    • Benjamin Pigeau
    • , Grégoire de Loubens
    • , Olivier Klein
    • , Andreas Riegler
    • , Florian Lochner
    • , Georg Schmidt
    •  & Laurens W. Molenkamp
  • Letter |

    Topological insulators are bulk insulators beneath conducting surface states with very special properties. By doping these surface states with iron, the surface band structure can be explored and controlled.

    • L. Andrew Wray
    • , Su-Yang Xu
    • , Yuqi Xia
    • , David Hsieh
    • , Alexei V. Fedorov
    • , Yew San Hor
    • , Robert J. Cava
    • , Arun Bansil
    • , Hsin Lin
    •  & M. Zahid Hasan
  • Letter |

    Graphene has a random edge structure. According to theory, this dirty and random edge affects the topological nature of bilayer graphene, which accounts for measurement discrepancies across different experimental probes.

    • Jian Li
    • , Ivar Martin
    • , Markus Büttiker
    •  & Alberto F. Morpurgo
  • Letter |

    By varying the voltage on an isolated gate electrode beneath a graphene sheet, the ionization state of cobalt atoms on its surface can be controlled. This enables the electronic structure of individual ionized atoms, and the resulting cloud of screening electrons that form around them, to be obtained with a scanning tunnelling microscope.

    • Victor W. Brar
    • , Régis Decker
    • , Hans-Michael Solowan
    • , Yang Wang
    • , Lorenzo Maserati
    • , Kevin T. Chan
    • , Hoonkyung Lee
    • , Çağlar O. Girit
    • , Alex Zettl
    • , Steven G. Louie
    • , Marvin L. Cohen
    •  & Michael F. Crommie
  • Letter |

    The rotation of polarized light in certain materials when subject to a magnetic field is known as the Faraday effect. Remarkably, just one atomic layer of graphene exhibits Faraday rotations that would only be measurable in other materials many hundreds of micrometres thick.

    • Iris Crassee
    • , Julien Levallois
    • , Andrew L. Walter
    • , Markus Ostler
    • , Aaron Bostwick
    • , Eli Rotenberg
    • , Thomas Seyller
    • , Dirk van der Marel
    •  & Alexey B. Kuzmenko
  • Letter |

    A three-dimensional periodic structure focuses acoustic waves to a spot size that is one fiftieth of the wavelength—beating the classical diffraction limit by a long way. The device could lead to improved resolution for ultrasound imaging.

    • J. Zhu
    • , J. Christensen
    • , J. Jung
    • , L. Martin-Moreno
    • , X. Yin
    • , L. Fok
    • , X. Zhang
    •  & F. J. Garcia-Vidal
  • Letter |

    The complex wrinkling patterns produced when a sheet or membrane is compressed are often difficult to predict. Observations of unexpected spatial period-doubling bifurcation instability in the wrinkling of a rigid membrane attached to a soft substrate can be described within a framework similar to that used for the parametric resonance of nonlinear oscillators.

    • Fabian Brau
    • , Hugues Vandeparre
    • , Abbas Sabbah
    • , Christophe Poulard
    • , Arezki Boudaoud
    •  & Pascal Damman

Articles

  • Article |

    The Landau–Zener model of a two-state system is a standard method for studying quantum dynamics. This textbook example of single-particle dynamics has now been generalized to a many-body system represented by two coupled ultracold Bose liquids.

    • Yu-Ao Chen
    • , Sebastian D. Huber
    • , Stefan Trotzky
    • , Immanuel Bloch
    •  & Ehud Altman
  • Article |

    An array of nanomagnets in a kagome lattice structure should support the creation and separation of oppositely charged monopoles, which are connected by Dirac strings of flipped dipoles. And indeed, such monopoles and their Dirac strings can be observed at room temperature.

    • Elena Mengotti
    • , Laura J. Heyderman
    • , Arantxa Fraile Rodríguez
    • , Frithjof Nolting
    • , Remo V. Hügli
    •  & Hans-Benjamin Braun
  • Article |

    Tunnelling measurements reveal the emergence of a thickness-dependent in-built potential across LaAlO3 thin films grown on SrTiO3 substrates. As well as being useful for developing novel LaAlO3/SrTiO3 devices, these observations help explain the origin of the two-dimensional electron gas that is known to arise at the interface between these two insulators.

    • Guneeta Singh-Bhalla
    • , Christopher Bell
    • , Jayakanth Ravichandran
    • , Wolter Siemons
    • , Yasuyuki Hikita
    • , Sayeef Salahuddin
    • , Arthur F. Hebard
    • , Harold Y. Hwang
    •  & Ramamoorthy Ramesh
  • Article |

    Raman amplification has been proposed as a means to generate high-power laser pulses without the bulky and expensive components of conventional lasers, but with limited success. Large-scale three-dimensional simulations enable researchers to identify conditions under which these limitations might be overcome.

    • R. M. G. M. Trines
    • , F. Fiúza
    • , R. Bingham
    • , R. A. Fonseca
    • , L. O. Silva
    • , R. A. Cairns
    •  & P. A. Norreys