Volume 14 Issue 9, September 2018

In praise of the Fields Medal.

Cooling molecules down to their ground state is an ongoing challenge for atomic and molecular physicists. Further steps in this journey have recently been made, with promising implications.

The properties of bismuth have long defied expectation, casting it just outside the bounds of almost every category. Now topology joins the list, as its electronic structure once deemed trivial turns out to have higher-order topology.

The realization of a new topological state using an electrical-circuit approach establishes a flexible scheme that should enable further explorations into uncharted territory and, equally importantly, make experiments with topological states more broadly accessible.

Applications of spintronics often require angular momentum to be moved from place to place. A possible observation of spin superfluidity may point the way toward the transport of spin angular momentum across an insulating sample with no dissipation or energy loss.

Understanding how natural surfaces repel foulants by wrinkling seems like a simple matter of elasticity. But the nonlinear behaviours that emerge from dimensional effects make for some intriguing new physics.

Recent experiments demonstrate that effects arising from quantum geometrical phases and band structure topology can coexist in two-dimensional materials, and can be addressed via optoelectronic experiments.

Magnetically tunable scattering resonances between strontium and rubidium atoms are observed in an ultracold experiment, opening the door to exploring quantum many-body physics with new designed molecules.

By coupling photons in two distinguishable modes to separate transitions of a single atom, strong correlations between photons are created. The technique makes all-optical switching and sensing possible at the single-photon level.

Laser cooling of optically trapped diatomic molecules CaF to sub-Doppler temperatures has been achieved. The technique provides an alternative approach towards the production of ultracold polar molecules.

Calculating the amount of radiation that can ultimately be extracted from free electrons near an arbitrary material structure is a challenge. Now, an upper limit to the spontaneous photon emission of electrons is demonstrated, regardless of geometry.

Optoelectronic experiments show that a monolayer of WTe₂ is a material that simultaneously has topological electronic states and electron wavefunctions with a dipole in their Berry curvature.

Spins are transmitted over a distance of 5 μm through a piece of antiferromagnetic graphene. This shows that graphene can be a platform to explore the fundamental physics of spin transport in antiferromagnets for application in spintronics.

Transport measurements performed on MoGe superconducting nanowires reveal a quantitative agreement with quantum critical behaviour driven by a pair-breaking mechanism.

The study of the band structure and crystal symmetry of the semimetal bismuth indicates that this material is a higher-order topological insulator hosting robust one-dimensional metallic states on the hinges of the crystal.

The realization of a two-dimensional quadrupole topological insulator—featuring gapless corner states but an otherwise insulating bulk and edge—establishes electrical circuits as a versatile platform for implementing topological band structures.

Quantum Hall states are observed in monolayer graphene at even-denominator fractional filling of the lowest Landau level. This is linked to transitions in the spin and valley structure of the ground state.

A new type of skyrmion is identified in the chiral magnetic material Cu₂OSeO₃ at low temperature. This is the first time that a single material has been shown to exhibit more than one distinct skyrmion phase.

Perfect transmission of sound waves through a strongly disordered environment is demonstrated using a set of speakers that provide exactly the right input to counteract scattering by the disorder. These principles can also be applied to light.

Natural surfaces better their synthetic counterparts at coping with biofouling. A characterization of topography-induced delamination reveals a mechanism whereby elastic energy drives the crack propagation that facilitates surface renewal.

Biofilms of rod-shaped bacteria can grow from a two-dimensional layer of founder cells into a three-dimensional structure with a vertically aligned core. Here, the physics underlying this transition is traced down to the properties of individual cells.

A violation of Lorentz symmetry would represent a fundamental departure from the physics of the standard model. Searching for anomalous neutrino oscillations, the IceCube collaboration reports no violation, and puts stringent bounds on its existence.

Solid angle is an ancient notion with modern relevance. A one-page primer by Ben Kravitz.