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Volume 578 Issue 7794, 13 February 2020

Triangular momentum

Electrically driven semiconductor lasers are one of the most common types of laser and are widely used in our daily lives, from optical-fibre communication to laser printing and barcode readers. But the performance of these lasers is affected by semiconductor defects — damage or imperfections introduced during fabrication and packaging. In this week’s issue, Qi Jie Wang, Yidong Chong, Baile Zhang and their colleagues present a terahertz laser based on a quantum cascade laser that suggests such problems might be solved by taking advantage of the topological properties of light. By creating a triangular interface between two differently oriented photonic crystal lattices (as shown on the cover), the authors create topological edge states that can emit terahertz radiation even if there are sharp corners and defects present. As the laser is driven electrically, it could open the way for topological systems to find practical applications.

Cover image: Songdi Technology (Beijing) Co, Ltd.

This Week

News in Focus

Books & Arts




    News & Views

  • News & Views |

    Devices known as quantum cascade lasers produce useful terahertz radiation, but are typically highly sensitive to fabrication defects. This limitation has now been overcome using a property called topological robustness.

    • Sunil Mittal
    • Edo Waks
  • News & Views |

    Prussian blue analogues are archetypes of coordination solids, in which metal ions are bridged by ligands to form extended network structures. An analysis reveals a surprising ordering of the gaps found in their crystal lattices.

    • Adam Jaffe
    • Jeffrey R. Long
  • News & Views |

    Healthy cells in smokers’ lungs have a high burden of mutations, similar to the mutational profile of lung cancer. Surprisingly, ex-smokers’ lungs have a large fraction of healthy cells with nearly normal profiles.

    • Gerd P. Pfeifer
  • News & Views Forum |

    Does time spent using digital technology and social media have an adverse effect on mental health, especially that of adolescents? Here, two scientists discuss the question, and how digital devices might be used to improve well-being.

    • Jonathan Haidt
    • Nick Allen
  • Reviews

  • Articles

  • Article |

    The three-dimensional structure of all cloud complexes in the solar neighbourhood is revealed, showing a narrow and coherent 2.7-kpc arrangement of dense gas, in disagreement with the Gould Belt model.

    • João Alves
    • Catherine Zucker
    • Gregory M. Green
  • Article |

    A topological laser based on the valley degree of freedom in a compact photonic crystal can be pumped electrically, bringing topological physics concepts closer to real-life applications.

    • Yongquan Zeng
    • Udvas Chattopadhyay
    • Qi Jie Wang
  • Article |

    The growth of single-crystal Prussian blue analogues and their analysis using X-ray diffuse scattering reveals diverse, non-random vacancy arrangements and information about the micropore-network characteristics of these materials.

    • Arkadiy Simonov
    • Trees De Baerdemaeker
    • Andrew L. Goodwin
  • Article |

    This analysis of the exchange of air pollution amongst the contiguous United States finds that, on average, around half of the early deaths caused by a state’s air pollution occurs outside that state, with different contributions by different emission sectors and chemical species.

    • Irene C. Dedoussi
    • Sebastian D. Eastham
    • Steven R. H. Barrett
  • Article |

    Whole-genome sequencing of normal bronchial epithelium from 16 individuals shows that tobacco smoking increases genomic heterogeneity, mutational burden and driver mutations, whereas stopping smoking promotes replenishment of the epithelium with near-normal cells.

    • Kenichi Yoshida
    • Kate H. C. Gowers
    • Peter J. Campbell
  • Article |

    In a mouse model, aryl hydrocarbon receptor signalling in enteric neurons is revealed as a mechanism that helps to maintain gut homeostasis by integrating the luminal environment with the physiology of intestinal neural circuits.

    • Yuuki Obata
    • Álvaro Castaño
    • Vassilis Pachnis
  • Article |

    A silkworm model recapitulates key steps of Zucchini-mediated cleavage of pre-pre-piRNA and provides insights into Zucchini-mediated and -independent pathways that generate pre-piRNAs, which converge to a common piRNA maturation step.

    • Natsuko Izumi
    • Keisuke Shoji
    • Yukihide Tomari
  • Article |

    A combination of optical tweezers and fluorescent-particle tracking is used to dissect the dynamics of the Hsp100 disaggregase ClpB, and show that the processive extrusion of polypeptide loops is the mechanistic basis of its activity.

    • Mario J. Avellaneda
    • Kamila B. Franke
    • Sander J. Tans
  • Article |

    Crystal structure of the Plasmodium falciparum hexose transporter PfHT1 reveals the molecular basis of its ability to transport multiple types of sugar as efficiently as the dedicated mammalian glucose and fructose transporters.

    • Abdul Aziz Qureshi
    • Albert Suades
    • David Drew
  • Matters Arising

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