Volume 16 Issue 5, May 2020

Astrophysical neutrinos could originate from blazars, but their modelling is challenging. Instead, the source of cosmic neutrinos could be a special yet unidentified class in which jets burrow through stellar material and produce neutrinos.

Pioneer of condensed-matter physics.

Single rare-earth ions are hard to observe and even harder to use as qubits. However, with the help of coupling to an optical cavity and clever engineering of selection rules, a big step has been taken to establish their new role in the quantum world.

Despite the wide use of mode-locked lasers, no general theory for mode-locking exists. An attractor dissection approach provides some intuitive understanding of the complex dynamics in one type of mode-locking.

An ultra-cold atomic gas is used to image a phase transition in an iron pnictide with micrometre resolution.

Spin ice is known as the magnetic analogue of ordinary ice, where the behaviour of its spins closely mirrors that of protons in water ice. It now has a sibling based on higher-order magnetic octupoles.

The choice of the physical system that represents a qubit can help reduce errors. Encoding them in the quadrature space of a superconducting resonator leads to exponentially reduced bit-flip rates, while phase-flip errors increase only linearly.

A trapped quantum gas and optical microscopy are simultaneously employed to measure the nematicity of an iron-based superconductor. This demonstrates the potential of quantum gases to be used for scanning microscopy of quantum materials.

Placing two Bernal-stacked graphene bilayers on top of each other with a small twist angle gives correlated states. As the band structure can be tuned by an electric field, this platform is a more varied setting to study correlated electrons.

One way of producing Majorana fermions for topological quantum computing is to induce superconductivity in other topological states. Here, the proximity effect does this for the quantum spin Hall effect state in a 2D material.

Small-angle neutron scattering measurements show that the vortices of the heavy-fermion compound UPt₃ possess an internal degree of freedom in one of its three superconducting phases, implying the breaking of time-reversal symmetry in the bulk.

Bound states at zero energy are observed at the ends of a line defect formed of atomic vacancies on the surface of a high-temperature superconductor. This indicates the possible presence of Majorana modes.

Spectroscopic study of the low-energy excitations in magnetite Fe₃O₄ shows the signatures of its charge-ordered structure involved in the metal–insulator transition, whose building blocks are the three-site small polarons, termed trimerons.

A detailed neutron-scattering study reveals a quantum spin liquid behaviour in Ce₂Sn₂O₇ originating from its higher-order magnetic multipolar moments acting on the geometrically frustrated pyrochlore lattice.

An imaging study of planarian flatworm brains demonstrates that densely packed neural tissues seem to have packing configurations commensurate with a jammed state.

The Double Chooz collaboration reports the neutrino oscillation parameter θ₁₃ from a measurement of the disappearance of reactor anti-electron neutrinos with the total neutron capture technique.

Mode-locking of lasers can be understood as self-organization, and the three-dimensional case of spatiotemporal mode-locking can described using attractor dissection theory, which helps develop an intuition for this complex case.

The modes of the radiation field generated from an emitter are usually determined by the eigenstates of the surrounding environment. However, this scenario breaks down in a non-Hermitian system, at the spectral degeneracy known as an exceptional point.

At high temperature, the heat diffusion in an insulator is expected to be dominated by entirely classical phonon dynamics. But theoretical study shows that the transport lifetime is subject to a quantum-mechanical bound related to the sound velocity.

Experiments on the deformation and bursting of elastic capsules impacting rigid walls are reported, revealing an analogy to the impact of liquid drops. The developed model for macroscopic objects could potentially be expanded to microscopic scales.

The mathematical modelling of how information spreads in social networks has latterly gained fresh urgency. A study of realistic structured populations now identifies the threshold at which the propagation of rumours becomes contagious, thereby inducing a phase transition.

The tool of choice to measure optical frequencies with extremely high precision is the optical frequency comb. Camille-Sophie Brès explains what makes this technique so powerful.