Volume 9 Issue 12, December 2013

Remember, remember 23 November: it's 'The Day of the Doctor'.

Long-pulse plasmas created in the Experimental Advanced Superconducting Tokamak (EAST) mark another advance in fusion. The Chinese tokamak now demonstrates a method for controlling the instabilities at the plasma edge that might otherwise limit the performance of prototypical fusion power plants such as ITER.

Light pulses with positive and negative effective masses are now generated using optical fibres. Nonlinear interactions between the two can then create self-accelerating pulse pairs, opening a new route to pulse steering.

The spin lifetime of a paramagnetic molecule on a superconducting surface is increased by orders of magnitude thanks to the effect of the superconducting gap, leading to improved control of molecular spin systems.

Small Fermi surfaces have been observed by quantum oscillations in the YBCO family of copper oxide superconductors, but until now it has been unclear whether they are specific to YBCO or universal to all underdoped cuprates.

High-cadence images link the phenomena required for particle acceleration at the Sun. A plasmoid-driven shock wave accelerates electrons in intermittent bursts.

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 metal has an underlying Fermi surface that gives rise to quantum oscillations. So far, quantum oscillation measurements in the superconductor YBCO have been inconclusive owing to the structural complexities of the material. Quantum oscillations in a Hg-based cuprate—with a much simpler structure—help to establish the origin and universality of the oscillations.

When a paramagnetic molecule is placed on a superconducting surface the lifetime of its spin excitations increases dramatically. This effect, caused by the depletion of the electronic states within the energy gap at the Fermi level, could find application in coherent spin manipulation.

Ultracold atoms in optical lattices are used to study various phenomena in condensed-matter physics, such as magnetism. A lattice-shaking technique can induce a strong effective spin-interaction, leading to the formation of ferromagnetic domains.

Confined within a porous aerogel, superfluid ³He loses its long-range order owing to random microscopic disorder, and becomes a glassy superfluid. Intriguingly, this effect can be switched off and the superfluidity restored.

An action generates an equal and opposite reaction. If it were possible, however, for one of the two bodies to have negative mass, they would accelerate each other. A situation analogous to this is now realized in an optical system. Solitons moving in an optical mesh lattice exhibit either an effective positive or negative mass, thus enabling observation of self-acceleration.

The intensity of optically-pumped fluorescence generated from a single atomic defect in diamond can be reduced by 80% in just 100 ns by applying infrared laser light. This result demonstrates the possibility of using these so-called nitrogen–vacancy centres to create optical switches that operate at room temperature.

Femtosecond pulses from X-ray free-electron lasers offer a powerful method for observing the coherent dynamic of phonons in crystalline materials, it is now shown. This time-resolved spectroscopic tool could provide insight into low-energy collective excitations in solids and how they interact at a microscopic level to determine the material’s macroscopic properties.

In the band theory of solids, the topological properties of Bloch bands are characterized by geometric phases. For cold atoms moving in a one-dimensional optical potential the geometric phase can be measured directly using Bloch oscillations and Ramsey interferometry.

Superparamagnetism (preferential alignment of spins along an easy axis) is a useful effect for spintronic applications as it prevents spin reversal. It is now shown that high-spin quantum dots can become magnetically anisotropic when coupled to nearby ferromagnets—‘artificial’ superparamagnets.

A room-temperature motion sensor with record sensitivity is created using a levitating silica nanoparticle. Feedback cooling to reduce the noise arising from Brownian motion enables a detector that is perhaps even sensitive enough to detect non-Newtonian gravity-like forces.

A combination of measurements from the Solar Dynamics Observatory and radiospectroscopy data from the Nançay Radioheliograph now details the mechanism that connects coronal mass ejections from the sun and the acceleration of particles to relativistic speeds. A spatial and temporal correlation between a coronal ‘bright front’ and radio emissions associated with electron acceleration demonstrates the fundamental relationship between the two.

A high-confinement plasma that is potentially useful for controlled fusion has now been sustained for over 30 s. The Experimental Advanced Superconducting Tokamak in Hefei, China, achieved this record pulse length by first confining the plasma using lithium-treated vessel walls, and then maintaining it with a so-called lower hybrid current drive.