Articles in 2020

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  • Manipulating weakly bound helium dimers with ultrafast laser pulses reveals their quantum behaviour. This method opens a route towards studying the low-energy dynamics of other exotic and fragile quantum states.

    • Daniel Rolles
    News & Views
  • Ultrashort laser fields applied to a helium dimer are able to tune the interactions between two helium atoms. A video of the dimer’s response to this localized disturbance shows the effect of dissociation and alignment of the wave packets.

    • Maksim Kunitski
    • Qingze Guan
    • Reinhard Dörner
  • The uncertainty associated with epidemic forecasts is often simulated with ensembles of epidemic trajectories based on combinations of parameters. We show that the standard approach for summarizing such ensembles systematically suppresses critical epidemiological information.

    • Jonas L. Juul
    • Kaare Græsbøll
    • Sune Lehmann
  • A general approach to derive direction-dependent complex refractive indices close to zero produces infinite families of time-reversible and infinite families of time-irreversible electromagnetic materials, without invoking the concept of topology.

    • S. A. R. Horsley
    • M. Woolley
  • A scientist’s legacy is defined not only by their research but also by their teaching. Stronger efforts should be made to preserve and celebrate the exposition of physics at all levels.

  • Within the Hartree atomic unit systems, the Schrödinger equation becomes parameter free. But there’s more to it than making a student’s life easier, as Gordon Drake and Eite Tiesinga recount.

    • Gordon W. F. Drake
    • Eite Tiesinga
    Measure for Measure
  • The interplay of topological properties and non-Hermitian symmetry breaking has been implemented for a range of classical-wave systems. Recent advances, challenges and opportunities are reviewed across the different physical platforms.

    • Corentin Coulais
    • Romain Fleury
    • Jasper van Wezel
  • Three-dimensional structures of vortex loops in a bulk micromagnet GdCo2 have been observed using X-ray magnetic nanotomography. The cross-section of these loops consists of a vortex–antivortex pair stabilized by the dipolar interaction.

    • Claire Donnelly
    • Konstantin L. Metlov
    • Sebastian Gliga
  • A class of biological matter including elongated cells and filaments can be understood in the framework of active nematic liquid crystals. Within these systems, topological defects emerge and give rise to remarkable collective behaviours.

    • M.-A. Fardin
    • B. Ladoux
    News & Views
  • Topological defects in active nematic systems such as epithelial tissues and neural progenitor cells can be associated with biological functions. Here, the authors show that defects can play a role in the layer formation of the soil bacterium Myxococcus xanthus.

    • Katherine Copenhagen
    • Ricard Alert
    • Joshua W. Shaevitz
  • Bacteria are able to move as vast, dense collectives. Here the authors show that slow movement is key to this collective behaviour because faster bacteria cause topological defects to collide together and trap cells in place.

    • O. J. Meacock
    • A. Doostmohammadi
    • W. M. Durham
  • High-harmonic generation up to the seventh harmonic is observed from the intrinsic three-dimensional topological insulator BiSbTeSe2. The parallel components of the even-order harmonics arise directly from the topological surface states.

    • Ya Bai
    • Fucong Fei
    • Peng Liu
  • When molecular model systems, such as polycyclic aromatic hydrocarbons, are ionized by ultrashort extreme ultraviolet pulses, their relaxation path proceeds via electron–phonon scattering, linking molecules to typical solid-state matter behaviour.

    • Laura Cattaneo
    News & Views
  • Spin currents are generated from an antiferromagnet/heavy-metal heterostructure using optical excitation on picosecond timescales. This will have applications in antiferromagnetic spintronics.

    • Hongsong Qiu
    • Lifan Zhou
    • Peiheng Wu