Volume 14 Issue 12, December 2018

Modern physics edged mechanics out into the wilds of engineering. But multidisciplinary interest in pattern formation has moved it back into the mainstream, bringing with it interest from other fields — as this summer’s Solvay Workshop demonstrated.

The Large Hadron Collider has completed its second data-taking period. For the next two years, the accelerator will shut down and the experiments will undergo major upgrades. Here’s a take on our past achievements — and a preview of the future.

The axial symmetry of tokamaks benefits plasma confinement but hinders control. Experiments have now proven that optimized non-axisymmetric magnetic fields can provide much improved control without degrading the plasma confinement.

Mercury isotopes are unique in exhibiting dramatic differences in their nuclear shapes. The analysis of over more than twenty Hg isotopes now shows that this follows from the influence of single-particle effects on the collective properties of a nucleus.

The simulation of strongly correlated quantum phases using ultracold atoms in optical lattices was first proposed 20 years ago. In the wake of that pioneering idea, quantum simulations are now widely pursued in experiments across the world.

Many microorganisms use light-sensitive receptors to migrate. A case in point is the microalga Euglena gracilis, which avoids light intensity increases by swimming in polygonal trajectories — providing an elegant solution to navigational challenges.

Spectroscopy and shell model calculations reveal the ¹⁸¹Hg isotope as the endpoint of the shape-staggering of Hg nuclei, a consequence of neutron removal which arises from the interplay of single-particle and collective degrees of freedom.

Superradiance is reported from an ensemble of nitrogen–vacancy centres coupled to a microwave resonator in the fast cavity limit.

Non-equilibrium Bose–Einstein condensation of 7 ± 2 photons is observed in a sculpted dye-filled microcavity. The small number of particles allows the authors to access and characterize the non-equilibrium dynamics of the bosonic modes.

A periodic pattern of Cooper pairs is observed at the atomic scale and is shown to be correlated with the local strength of the superconductivity. This reveals a new interplay between different ordered states in the cuprates.

A new noise spectroscopy technique shows that charges localized as polarons trapped at impurity sites mediate perpendicular ‘c-axis’ electronic transport in cuprate superconductors.

Water drops placed at rest on flat, hot solids are found to rotate and spontaneously propel themselves in the direction of their rotation. The effect is due to symmetry breaking of the flow inside the drop, which couples rotation to translation.

Suspended clusters of honeybees withstand dynamic mechanical forcing from their environment. Experiments and simulations suggest that collective stability relies on individual bees responding to local variations in strain.

Biexcitons play an important role in determining the optical properties of transition metal dichalcogenide monolayers, but their precise structure is poorly understood. Using a combination of ultrafast spectroscopy and theory, the origin of their fine structure is revealed.

Quantum fluctuations in space and time can now be directly imaged using a scanning superconducting quantum interference device. The technique allows access to the local dynamics of a system close to a quantum phase transition.

A rigid particle moving along a soft wall feels a repulsive force that can reduce its drag. Evidence now suggests that for thin enough walls the particle can be displaced appreciably—a finding that may have implications for biological membranes.

A single-celled organism exhibits complex swimming behaviours in response to changes in light intensity. Modelling and experiments suggest that the swimmer exploits phase relations between its photoreceptor and orientation to enable navigation.

A theoretical and numerical approach, validated by experiments at the KSTAR facility, shows how magnetohydrodynamic instabilities in tokamak plasmas can be efficiently controlled by a small relaxation of the confining field into a 3D configuration.

Bart Verberck reflects on measuring the speed of light, its role in metrology, and special relativity.