Articles in 2010

The experimental demonstration of heat currents driving the injection of spins from a ferromagnetic into a non-magnetic metal establishes a new source of pure spin currents. The approach might provide an alternative mechanism for switching processes in memory devices and for other ‘spintronics’ applications.

When doped with copper, the topological insulator Bi₂Se₃ becomes superconducting. But for new physics and applications the search is not for just any superconductor; the material must retain its topological character. And indeed that is the case with doped Bi₂Se₃.

Erwin Schrödinger introduced in 1935 the concept of ‘steering’, which generalizes the famed Einstein–Podolsky–Rosen paradox. Steering sits in between quantum entanglement and non-locality — that is, entanglement is necessary for steering, but steering can be achieved, as has now been demonstrated experimentally, with states that cannot violate a Bell inequality (and therefore non-locality).

Diffraction conventionally limits the length scale on which spins can be optically probed. A new technique that uses doughnut-shaped beams of light to select just one nitrogen-vacancy centre, by suppressing the fluorescence from those around it, enables single-spin detection, imaging and manipulation with nanoscale resolution.

Humans tend to explore unknown locations, but preferentially return to familiar places. The interplay between these two basic behaviours accounts for many of the scaling relations observed in human-mobility patterns.

Single crystals of a two-dimensional quantum spin system with geometric frustration lead to the observation of a ‘pinwheel’ valence-bond ground state. In this case, the distortion of the ideal kagome lattice structure helps to stabilize the quantum spin state.

Introducing a phase shift between diffracted and undiffracted light from a sample is one of the oldest techniques for generating phase contrast in optical microscopy. A similar approach should help improve the contrast and clarity of images collected by scanning X-ray microscopy.

Extensive data sets of trajectories of mobile-phone users provide a new basis for modelling human mobility. Random-walk models can capture some aspects, but go only so far. Now, two governing principles for human mobility are proposed, exploration and preferential return, paving the way to a more appropriate microscopic model for individual human motion.

In one-dimensional systems, phase transitions at finite temperature are deemed impossible, because long-range correlations are destroyed by thermal fluctuations. Theoretical work now shows that, nonetheless, a phase transition at finite temperature can occur in a one-dimensional gas of weakly interacting bosons in a random environment

The finding that a network of 'leaky' neurons can sustain activity-burst avalanches links the science of criticality to that of realistic brain models.

Self-organized criticality has been observed in a number of complex systems, including neuronal networks. Another property of cortical networks is that a high proportion of neurons collectively alternate between high activity (so-called up states), and quiescence (down states). Theoretical work now shows these two phenomena are intimately related.

Dark energy is a prime target in the proposed US astronomy programme.

Significant work in particle physics bears his name, but the list of Nobel winners does not.

A revisiting of Heisenberg's uncertainty principle in the light of modern quantum information theory yields a formulation that takes into account the reduction in uncertainty from the point of view of a quantum observer.

The community of statistical physicists meets every three years on a different continent at the series of STATPHYS conferences to define the state-of-the-art in the field and to outline its possible evolution.

Real-space visualizations of the Pauli exclusion principle in clouds of cold fermions show quantum mechanics at work, and suggest a new tool for measuring nanokelvin temperatures.