Letters in 2020

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  • 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
    Letter
  • 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
    Letter
  • 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
    Letter
  • 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
    Letter
  • 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
    Letter
  • The coherence of a close-to-ideal laser beam can be quadratically better than what was believed to be the quantum limit. This new Heisenberg limit could be attained with circuit quantum electrodynamics.

    • Travis J. Baker
    • Seyed N. Saadatmand
    • Howard M. Wiseman
    Letter
  • Recently, a framework was introduced to model three-dimensional physical networks, such as brain or vascular ones, in a way that does not allow link crossings. Here the authors combine concepts from knot theory and statistical mechanics to be able to distinguish between physical networks with identical wiring but different layouts.

    • Yanchen Liu
    • Nima Dehmamy
    • Albert-László Barabási
    Letter
  • Transport measurements show that spontaneous symmetry breaking plays a crucial role in the correlated insulating and metallic states in twisted double bilayer graphene.

    • Minhao He
    • Yuhao Li
    • Matthew Yankowitz
    Letter
  • Bacteria live in heterogeneous environments, so it is important to investigate their behaviour in porous media. Here the authors show that flow disorder enhances the effect of chemical gradients in micropockets in a porous medium, which then aid the transport of bacteria.

    • Pietro de Anna
    • Amir A. Pahlavan
    • Ruben Juanes
    Letter
  • By incorporating a ferromagnetic layer in their superconductor–semiconductor nanowire hybrid device, Vaitiekėnas et al. show that zero-bias peaks—potential Majorana bound states—can be induced without an external magnetic field.

    • S. Vaitiekėnas
    • Y. Liu
    • C. M. Marcus
    Letter
  • Electrons and holes in doped quantum wells cannot form bound states from usual Coulomb interaction. However, when the system is embedded in a cavity, the exchange of photons provides an effective attraction, leading to the creation of bound excitons.

    • Erika Cortese
    • Ngoc-Linh Tran
    • Simone De Liberato
    Letter
  • Composite fermions can be tuned to very low effective density in a clean two-dimensional electron gas, which allows the formation of a Bloch ferromagnet.

    • Md Shafayat Hossain
    • Tongzhou Zhao
    • M. Shayegan
    Letter