The ground state of electrons in undoped graphene at high magnetic field is still not fully known. Measurements of thermal conductance could help to differentiate between the various theoretically proposed candidates. Delagrange et al. report such measurements and find that the thermal conductivity is vanishingly small, in contradiction to many of the predictions.

See Delagrange et al.

How cells manage the internal energetic budget to drive mechanical and chemical dynamics is still an open question. Sheng Chen and collaborators show that the allocation of energy depends on how far the cell is from thermodynamic equilibrium.

See Sheng Chen et al.

Charge density waves are wave-like patterns in a material’s electron density that can behave collectively. Shaoxiang Sheng et al. show a direct real-space observation of these collective dynamics at the atomic scale in the transition metal dichalcogenide 2H-NbSe2. Their technique utilizes a terahertz pulse that is enhanced at the tip of a scanning tunnelling microscope to excite oscillations of the charge density wave that vary in magnitude and frequency on the scale of individual atomic impurities. Measuring the current through the tip reveals overlapping phase excitations originating from randomly distributed atomic defects in the surface and creates a spatially structured response of the charge density wave.

See Shaoxiang Sheng et al.

Anyons are particles that do not follow either Bose or Fermi statistics and can be found in quantum many-body systems that have a non-Abelian topological order. They can be used to encode and manipulate quantum information in a topologically protected manner, meaning that they are robust against some types of noise. Shibo Xu et al. have used a superconducting quantum processor to simulate non-Abelian topologically ordered states of the Fibonacci string-net model and demonstrate both braiding and fusion of Fibonacci anyons — operations that are required to implement quantum gates.

See Xu et al.

The formation of holes in epithelial tissue is important for development but can also lead to problems, including cancer, if the process does not work smoothly. Jian-Qing Lv and collaborators have tracked the nucleation, coalescence, and eventual formation of a network of holes in monolayer epithelioid tissues. In particular, they found a fracture–slip mechanism that takes place during hole coalescence and enables the breaking of multicellular bridges without deforming cells too strongly. These results show that the mechanics of living tissues are coordinated across multiple length scales so that holes can form with minimal risk of mechanical damage.

See Jian-Qing Lv et al.

Cells can pair up and form a rotating doublet. Linjie Lu and collaborators have shown that these rotations are spontaneously caused by an uneven distribution of myosin within cell cortices. This polarized distribution breaks the mirror symmetry of the doublet. These results highlight how active mechanical forces drive collective cell motion.

See Lu et al.

The existence of fluctuations in the metric of spacetime induced by quantum gravity would have an impact on neutrinos produced in cosmic-ray air showers. They would lose their quantum coherence, causing their flavour oscillations to change. The IceCube collaboration reports a search for this effect but finds no evidence for it, thus constraining the magnitude of anomalous decoherence from quantum gravity.

See IceCube Collaboration

Quantum devices need to be linked together in such a way that entanglement can be shared between them. Meesala et al. demonstrate a step towards this goal by developing a transducer capable of generating microwave-optical photon pairs that can be used to share non-classical correlations between an optical link and a superconducting quantum device.

See Meesala et al.

The way in which glassy materials age can be difficult to describe. The concept of material time allows for the description of this physical ageing in a linear way. Multispeckle dynamic light scattering experiments now provide experimental access to material time and show that intensity fluctuations become statistically reversible when referenced in this way.

See Böhmer

The dynamics of isolated quantum many-body systems far from equilibrium is a field of study that pertains to many situations, including ultracold atoms, quantum spin magnets, and quark–gluon matter. Here, magnetization measurements in a spinor atomic gas show a way to classify universal dynamics based on symmetry and topology.

See Huh et al. and Prüfer

The dynamics of complex systems are often modelled using low-rank matrices, but the formal validity of this method has not yet been confirmed. Thibeault et al. present an analysis of random networks and real-world data that sheds light on this low-rank hypothesis and its implications.

See Thibeault et al. and Gao

Non-Hermitian physics enables dynamic control of optical behaviour in real time, such as reflectionless scattering modes, which have now been demonstrated in a chaotic photonic microcavity.

See Jiang et al. and Stone