Volume 4 Issue 5, May 2008

Although a driven colloidal suspension is not at equilibrium, a systematic study shows that such a system can still undergo a phase transition — albeit to a randomly organized state.

The energy of an atom binding one photon in a cavity can be derived classically. But when two photons are bound to the atom, signatures of light quantization appear in the spectrum. These have now been observed in the optical domain.

Experiment has now proved the existence of the predicted three-dimensional 'topological insulator' in the semiconducting alloy Bi_1−xSb_x.

A systematic study of ionization and high harmonic generation in strong laser fields at long wavelengths confirms predictions made 40 years ago, and has important implications for the development of attosecond light sources.

The requirement for an object to be surrounded by empty space when imaged by coherent X-ray diffraction was once thought to be a fundamental limitation. A variant of coherent diffractive imaging proves this not to be the case, and substantially widens its potential use.

Is a rotating neutron star powered by rotational energy loss or by magnetic-field decay? The answer seems to be yes.

Control over the distribution of electrons in a relativistic particle beam enables the realization of a bright, narrow, tunable source of terahertz radiation.

Lasing in disordered media presents both theoretical challenges and practical opportunities.

A magnetic vortex trapped by a notch in a nanowire is no larger than 10 nm, but both the direction and polarity of the vortex can now be measured without applying a magnetic field. In this set-up, the vortex is therefore both stable and switchable for use in possible device applications.

Electric-field induced control of the magnetic ground state of a carbon nanotube quantum dot enables the orientation of injected spins to be reversed without using an external magnetic field.

Valuable insight into the influence of scattering from impurities on the peculiar electronic properties of graphene are gained by a systematic study of how its conductivity changes with increasing concentration of potassium ions deposited on its surface.

Nonlinear optics traditionally involves macroscopic atomic ensembles or solid-state crystals. The observation of a nonlinear two-photon resonance in a system consisting of one single atom trapped inside an optical cavity demonstrates nonlinear optics at the level of individual quanta.

A systematic experimental study of the ionization of argon by mid-infrared light confirms half-a-century-old predictions and paves the way to the development of brighter, shorter attosecond pulse sources.

A tunable source of coherent narrowband terahertz radiation is realized by using a laser to modulate the emission characteristics of a relativistic electron beam.

A powerful coherent diffractive X-ray imaging technique could enable next generation synchrotrons and free-electron lasers to study much larger samples than previously thought possible.

Spin-polarized neutrons are sensitive to magnetic fields, and they can relatively easily penetrate through matter. A new imaging technique uses these two properties for mapping the three-dimensional distribution of magnetic fields inside massive objects.

Grains, foams and colloids can behave as liquids or solids. Their flow is difficult to predict, often jamming. Such systems are far from equilibrium but there may now be a thermodynamic framework for granular media.

There are two major theories regarding the normal state of a high-temperature superconductor: that the ‘pseudogap’ state is either a disordered superconductor or a distinct and competing phase. But could it be both?

Laser-driven resolved sideband cooling of the resonant vibrational mode of a toroidal microcavity represents another step towards reaching the quantum ground state.

Random collisions between particles usually generate disorder in a system. But under certain conditions, particles in suspended in a liquid subjected to periodic shear forces can collide in a way that leads to fewer subsequent collisions and less disorder.

Change is not always for the best.