Volume 13 Issue 10, October 2017

The two-way symmetry of electromagnetic wave propagation can be broken effectively in optomechanical systems, enabling new devices that route photons in unconventional ways.

Vast beds of 'hair' coat many living systems, and usually exhibit shear-thinning behaviour — their flow resistance lessens with speed. But with geometric tweaks, such beds can also show shear-thickening and asymmetric ratchet-like behaviour.

A crystalline organic semiconductor that combines the long spin-relaxation times of organic semiconductors with the high charge-carrier mobilities typically found in inorganic semiconductors provides unprecedented prospects for organic spintronics.

With diverse polymorphisms and phase transitions that can be triggered using many methods, layered transition metal dichalcogenides are attractive materials for realizing novel topological states, as well as for a range of other applications.

Atomic interferometry measurements of the gravitational force on free-falling atoms provide improved constraints on certain scalar field theories trying to explain dark energy.

Bragg spectroscopy shows the evolution of gapless Goldstone modes and single-particle-like excitations in an atomic Fermi superfluid as it crosses from a Bardeen–Cooper–Schrieffer superfluid to the Bose–Einstein condensate regime.

In different applications the Gouy phase is used to describe broadband lasers, but new 3D measurements of the spatial dependence of a focused laser pulse show serious deviations from the Gouy phase.

Ultrahigh-resolution resonant inelastic X-ray scattering shows how dispersive charge density wave excitations influence the charge and lattice degrees of freedom in a high-T_c cuprate, pointing to a connection to the mysterious pseudogap state.

A hidden stripe-type charge ordering in multilayer iron selenide films on strontium titanate, resembling that in high-temperature cuprate superconductors, could help to explain the complex behaviour of this unusual iron-based superconductor.

A detailed neutron scattering study of the Shastry–Sutherland material SrCu₂(BO₃)₂ verifies the existence of a 4-spin plaquette singlet phase in this system.

An experimental study of the rare-earth intermetallic system LuPt₂In reveals a strong enhancement of superconductivity near the charge density wave quantum critical point. This represents an unusual counter-example to cuprates, in which superconductivity and charge density waves tend to compete.

Triggering and sustaining fusion reactions — with the goal of overall energy production — in a tokamak plasma requires efficient heating. Radio-frequency heating of a three-ion plasma is now experimentally shown to be a potentially viable technique.

In three-dimensional metals, topological objects known as Weyl nodes can arise from a crossing of the conduction and valence bands. Experiments under high magnetic fields show how Weyl nodes of opposite chiralities can move together to annihilate.

A demonstration of long-distance spin transport through an amorphous magnetic insulator shows that magnetic order is not required, and may not even be desirable, in materials for magnonic and spintronic applications.

A linear relationship between spin and momentum relaxation shows that the spin relaxation in an organic semiconductor crystal that has ultra-long spin lifetimes and coherent band-like transport is governed by the Elliott–Yafet mechanism.

Interactions between cells can affect the way they migrate, impacting processes like cancer invasion and wound healing. Experiments on cell colonies of moderate density show that these interactions can enhance motility by increasing persistence.

Cells rely on their proteins being positioned correctly for processes such as cell division and migration. A model based on Turing patterns provides an active mechanism for establishing this precise control in bacteria.

A bed of deformable hairs is shown to exhibit a nonlinear response to fluid flows. The biomimetic system suggests that hair-covered surfaces in living systems may function to reduce fluid drag as a means of minimizing excessive stresses.

Lubricated surfaces are known to display extreme liquid repellency. Such behaviour is now confirmed to be due to the formation of a film between the surface and the repelled liquid, with a thickness profile following the Landau–Levich–Derjaguin law.

Dimensional analysis is a powerful tool for assessing physical problems, reaffirms Tina Hecksher