Volume 15 Issue 8, August 2019

Availability of the source code should soon become the minimum standard for academic software. In addition, culture should shift to embrace code review and appropriate credit for the developers of reusable software.

The transport properties of many two-dimensional systems are strongly affected by the proximity of a periodic pattern. Colloidal particles are now shown to have preferred sliding routes due to competing symmetries between two unmatched crystalline surfaces.

A demonstration that Michael Berry’s legacy can inform our understanding of Lamb waves in stratified fluids serves as a reminder of the reach of topological thinking — as well as its potential utility.

A theoretical analysis of exotic superconductors suggests that it is possible to manipulate the state of their order parameter with light. This will help engineer devices from topological superconductors by patterning regions with different orders.

The measurement of the charge density wave energy gap in high-temperature superconducting cuprates uncovers new links between competing states.

A deterministic violation of the Bell inequality is reported between two superconducting circuits, providing a necessary test for establishing strong enough quantum entanglement to achieve secure quantum communications.

Strong quantum correlations in an ultracoherent optomechanical system are used to demonstrate a displacement sensitivity that is below the standard quantum limit.

A collective excitation behaving as a single emergent entity, known as a quasiparticle, often becomes unstable when encountering a continuum of many-body excited states. However, under certain conditions, the result can be totally different.

The Kondo effect—the screening of a magnetic impurity’s local moment by the electron Fermi sea in a metal—has been observed in a charge-insulating quantum spin liquid material, where the spinon excitations take the role of electrons.

AlPt is shown to be a chiral topological material with four-fold and six-fold degeneracies in the band structure. Fermi arc edge states span the whole Brillouin zone and their dispersion enables identification of the handedness of the chiral material.

This study presents a proposal for an all-optical method for manipulating chiral superconductors. Light pulses can switch the handedness of the chirality, potentially enabling controlled local writing of domain walls and associated Majorana modes.

The authors show that the energy gap of the charge density wave is strongly linked to that of the superconducting and pseudogap in several cuprates. This indicates that the same microscopic physics may drive all three phases.

Colloidal clusters are shown to undergo directional locking when driven across a patterned surface. The role of the Fourier components of the particle–surface interaction suggests a means of leveraging this behaviour for nanoscale manipulation.

A prediction of the existence of trapped acoustic-gravity waves in stratified fluids provides a platform for probing topological phenomena in the lab—with possible implications for astrophysical and geophysical flows.

According to the Unruh effect, for an accelerating observer the vacuum is filled with thermal radiation. Experiments now simulate this effect, recreating the statistics of Unruh radiation in the matter-wave field of a Bose–Einstein condensate.

Machine learning techniques have latterly gained currency in condensed-matter physics, for example by identifying phase transitions. An unsupervised machine learning algorithm that identifies topological order is now demonstrated.

Renormalization group calculations incorporate band structure and interaction effects on an equal footing. Applying this methodology to Ge-doped Pb₃Bi shows that this material is a chiral topological superconductor and hosts Majorana fermions.

The principle of gauge invariance in quantum electrodynamics may be violated by approximate models in the presence of strong light–matter interactions. A general approach solves gauge ambiguities and offers a way to construct gauge-invariant Hamiltonians.

A unified theory for the conduction of heat in materials is derived and shown to account for both the limiting regimes of periodic crystals and aperiodic glasses.

The long spin lifetimes observed in polymeric semiconductors hold promise for potential applications. A careful study untangles the main mechanism behind them.

The structural integrity of a cell’s nucleus is maintained by a polymer network known as the nuclear lamina. A simple biophysical theory reveals two regimes by which this network can rupture, depending on the structure of the nuclear envelope.

Microtubules vary their length by gaining and shedding tubulin dimers dynamically at both ends. But evidence now suggests that dimers may also be incorporated into the middle of the shaft—calling into question existing models of growth dynamics.

Stress relaxation in cell monolayers shows remarkable similarities with that of single cells, suggesting the rheology of epithelial tissues is mediated by the actomyosin cortex—with dynamics reminiscent of those on a cellular level.

A study of how migrating cells optimize their search efficiency in the absence of directional cues reveals a self-organizing system that mediates superdiffusive motion—and sheds light on how cells navigate noisy environments.

Cells migrating within a collective naturally have restricted access to their surroundings. Experiments on micropatterned substrates now show that this confinement can regulate epithelial migration—governing cell morphology, forces and velocity.

Superconducting quantum interference devices can accurately measure temperatures even below 1 mK, but there’s more to them — as Thomas Schurig explains.