Articles in 2013

The creation of Feshbach molecules by exploiting engineered spin–orbit coupling in a spin-polarized Fermi gas advances the experimental study of topological superfluidity in ultracold gases.

In open quantum systems the correlations between the system and its environment play an important role. A trapped-ion experiment demonstrates that these correlations can be detected without accessing or knowing anything about the environment or its interactions.

Assemblies of colloidal particles provide a micrometre-scale analogue of atomic and molecular liquids and solids. Now, real-time visualization of the liquid-solid transition in systems of spherical colloids reveals complex pathways involving precursors of hexagonal close-packed, body-centred cubic and face-centred cubic symmetry.

A careful revision of the rudiments of statistical physics shows that negative temperatures are artefacts of Boltzmann's approximate definition of entropy. Gibbs' version, however, forbids negative absolute temperatures and is consistent with thermodynamics.

Defects in silicon carbide can produce continuous-wave microwaves at room temperature. Spectroscopic analysis indicates a photoinduced inversion of the population in the spin ground states, which makes the defects a potential route to stimulated amplification of microwave radiation.

It is shown that for thermodynamics and statistical physics to be internally consistent, Gibbs’ original—rather than Boltzmann’s widely used—definition of entropy needs to be adopted. Consequently, negative absolute temperatures are strictly forbidden, and cold-atom gases are unlikely to be laboratory analogues to dark energy.

The mathematical connection between isostatic lattices—which are relevant for granular matter, glasses and other ‘soft’ systems—and topological quantum matter is as deep as it is unexpected.

Femtosecond pulses from X-ray free-electron lasers offer a powerful method for studying charged collective excitations in materials, and provide a potential route to identifying bosonic quasiparticles in condensed-matter systems.

Every scientist has an interest in their own citations, but regularly updated maps of citations across all of science are tracking what's hot and what's not.

When the atmospheric surface pressure is just right, a temperature difference can drive a continuous flow of rarefied gas through the soil matrix — a previously unrecognized process on Mars.

Magnetic monopoles continue to be elusive. However, an experiment now shows that the interaction of an electron beam with the tip of a nanoscopically thin magnetic needle—a close approximation to a magnetic monopole field—generates an electron vortex state, as expected for a true magnetic monopole field.

Microgravity experiments on a dust bed in a ‘drop tower’ set-up reveal the ability of martian soil to act as an efficient gas pump when heated by the Sun.

Networks that fail can sometimes recover spontaneously—think of traffic jams suddenly easing or people waking from a coma. A model for such recoveries reveals spontaneous ‘phase flipping’ between high-activity and low-activity modes, in analogy with first-order phase transitions near a critical point.