Volume 14 Issue 8, August 2018

David Hilbert famously argued that infinity cannot exist in physical reality. The consequence of this statement — still under debate today — has far-reaching implications.

The physicist Giancarlo Ghirardi passed away on 1 June 2018, after a life devoted to the foundations of quantum mechanics.

The ideas of topology are breaking ground in origami-based metamaterials. Experiments now show that certain shapes — doughnuts included — exhibit topological bistability, and can be made to click between different topologically stable states.

Magnetic tweezer measurements have revealed the forces associated with a star-shaped structure responsible for moving the sperm nucleus to the centre of the egg cell following fertilization.

The first campaign of the largest stellarator ever built, Wendelstein 7-X, has been successful, achieving high electron temperatures and minimal self-generated plasma current. This is very encouraging for future long-pulse, full-power operation.

An off-resonant radiofrequency modulation scheme applied to a strongly interacting superfluid Fermi gas reveals the presence of a Higgs mode — an oscillation of the amplitude of the superconducting order parameter.

α-RuCl₃, a promising candidate to realize the Kitaev model, has attracted great interest recently. Two types of fractional excitation—gauge fluxes and Majorana fermions—are observed, which contribute to the spin excitation gap in different ways.

Long-range ferromagnetic order in co-doped topological insulator thin films and their typical ferromagnetic domain behaviour is directly evidenced by low-temperature magnetic force microscopy.

A phase of strongly interacting electrons that has a spontaneous dipole moment is seen for the first time using an approach that images the electron's wavefunction through interference at an impurity.

A new type of exciton is observed in transition-metal dichalcogenide heterobilayers that is indirect in both real space and momentum space. It consists of a paired electron in MoS₂ at the K point and hole spread across MoS₂ and WSe₂ at the Γ point.

A superlattice consisting of SrIrO₃ and SrTiO₃ is shown to display a giant response to sub-tesla external magnetic fields—a direct consequence of its antiferromagnetic nature.

Origami-inspired metamaterial design gives rise to structures with kinematic properties dictated by the topology of their configuration space. The approach allows for well-defined metamaterial properties even in the presence of unpredictable forces.

The angle of Cherenkov radiation in one-dimensional photonic crystals can be controlled by making use of constructive interference. This feature allows new design of particle detectors with improved performance.

Years of data from atomic clocks around the world allow estimation of the variation of their rates with the spatial change of the solar potential. This allows the most precise null test of the local position invariance principle of general relativity.

The entanglement spectrum of a many-body quantum system encodes several of its properties. The construction of an artificial Hamiltonian that encodes the spectrum offers the possibility to probe it via quantum simulation or spectroscopy.

A Lorentz transmission electron microscopy study of a thin iron germanium film reveals the aggregation dynamics of skyrmions when pushed out of equilibrium.

Superconductivity is studied in the molecular solid K₃C₆₀ when it is pressurized and illuminated with short laser pulses. Similarities with the non-illuminated case show that superconductivity exists at higher temperatures than previously thought.

Non-equilibrium physics grants access to equilibrium free energies from the work performed on fluctuating systems—but only when the work itself is measurable. Relaxation fluctuation spectroscopy provides an alternative route to these energies.

To perform key processes like division, many cells use star-shaped polymeric aster structures to find their centre. Force measurements now reveal that an active spring mechanism regulates this process, suppressing noise to ensure precise centration.

Results from the first experimental campaign of the Wendelstein 7-X stellarator demonstrate that its magnetic-field design grants good control of parasitic plasma currents, leading to long energy confinement times.

Inspired to methods developed for the study of complex systems, a framework for predicting gross domestic product growth outperforms the accuracy of the five-year forecast of the International Monetary Fund.

Richard Davis refreshes our memory on the venerable metre.