Reviews & Analysis

Simple models have given us surprising insight into how animals flock, but most assume they do so through a homogeneous landscape. Colloidal experiments now suggest that a little disorder can have unexpected — and spectacular — effects.

Insights from the emerging field of branched flow are directing us towards a way of anticipating the effects of tsunamis. A framework linking bathymetric fluctuations to wave physics marks a promising step forward.

Reshaping network theory to describe the multilayered structures of the real world has formed a focus in complex networks research in recent years. Progress in our understanding of dynamical processes is but one of the fruits of this labour.

A milestone for quantum hydrodynamics may have been reached, with experiments on a black hole-like event horizon for sound waves providing strong evidence for a sonic analogue of Hawking radiation.

Going around an exceptional point in a full circle can be a non-adiabatic, asymmetric process. This surprising prediction is now confirmed by two separate experiments.

Dendritic cells use components of their cytoskeleton to both move and ingest pieces of infected cells. This competition for protein resources can give rise to a complex set of states that may be understood with an advection–diffusion model.

Due to their chirality, the massless fermions inside Weyl semimetals can take unusual paths that are governed by chiral dynamics, potentially providing a direct method to explore their topological nature.

Owing to the extreme sensitivity of a microscopic cantilever to optical forces, it is possible to uncover the fine structure of optical momenta and associated mechanical effects in evanescent fields.

Signatures of many-body localization have been observed in a one-dimensional chain of trapped ions, heralding new studies of the interplay between localization and long-range interactions.

The physical properties of ice are governed by its tetrahedral network of hydrogen bonds and the ice rules that determine the distribution of the protons. Deviations from the tetrahedral structure and violations of these rules can lead to surprising phenomena, such as the ferroelectric state now reported for thin films of epitaxial ice.

A wire moving at constant speed through superfluid helium can considerably exceed the Landau critical velocity.

Neutrinos from deep space can be used as astronomical messengers, providing clues about the origin of cosmic rays or dark matter. The IceCube experiment is leading the way in neutrino astronomy.

When it comes to star formation, dwarf galaxies perform very poorly. A possible explanation for this behaviour involves photoelectric electrons heating the star-forming gas.

Using optical lattices to trap ultracold atoms provides a powerful platform for probing topological phases, analogues to those found in condensed matter. But as these systems are highly tunable, they could be used to engineer even more exotic phases.

Although Dirac fermions in graphene can tunnel through potential barriers without reflection, two experiments show how they can temporarily be trapped inside nanoscale graphene quantum dots.

Chiral symmetry breaking is imaged in graphene which, through a mechanism analogous to mass generation in quantum electrodynamics, could provide a means for making it semiconducting.

Rashba spin–orbit coupling has already provided fertile physics and applications in spintronics but real-space imaging shows how the strength of this interaction varies on the nanoscale.

A renaissance of interest in a numerical technique known as the conformal bootstrap is surveyed, and its implications for the determination of critical exponents in a range of spin models is discussed.

The experimental observation of superconductivity that breaks spin-rotation symmetry in copper-doped Bi₂Se₃ provides a qualitatively distinct kind of unconventional superconducting behaviour — one that brings the importance of the spin–orbit interaction to the fore.