Articles in 2009

Measurements of the local response and noise during the ageing of a polymer film show deviations from the expected fluctuation–dissipation theorem. Moreover, scaling behaviour suggests a separate universality class for fragile glass formers.

During galaxy formation, the condensing matter can swirl into a new star or feed a central black hole. But what favours one mechanism over the other? It may be that there exist two critical surface densities of the matter cloud: a lower limit above which star formation occurs, and a higher threshold above which black holes form.

A neutron scattering study reveals that the magnetic fluctuations in an iron arsenide superconductor behave according to the conventional theories of metals, unlike the cuprate superconductors. Moreover, the magnetic spin-excitation energies are sufficient to mediate the Cooper pairs that form the superconducting state.

A structure that allows neutrons to be trapped in long-lived ‘whispering gallery’ states provides scientists with a potentially useful tool to study the interaction of neutrons with matter. It could also allow the development of quantum neutron optics.

A long-standing goal of experiments using cold atoms in optical lattices is to simulate the behaviour of strongly correlated electrons in solid-state systems. However, in these experiments, the atoms are confined to spatially inhomogeneous traps, whereas the desired information concerns homogeneous bulk systems. Theoretical work now proposes a way to connect the two types of system.

It is now shown that the semiconductor InSb becomes transparent to terahertz radiation when an appropriate magnetic field is applied. This effect has never been seen before, despite decades of research on InSb, and the phenomenon could find important applications in the burgeoning field of terahertz imaging.

Back-action, the effect of a measurement on the subject system, limits precision when determining position. This is of particular importance in nanomechanical oscillators, which could soon enter the quantum regime. A technique that avoids back-action by coupling the oscillator to a microwave resonator has now been demonstrated.

A demonstration of a 'two terminal' single-electron transistor governed by the magnetic anisotropy of ferromagnetic electrodes connected to a metal quantum dot could give birth to a new field of single-electron spintronics.

The observation of Hall quantization and complete lifting of the degeneracy in bilayer graphene at magnetic fields an order of magnitude lower than previously reported has important implications for an understanding of the role of many-body interactions in the exotic behaviour of bi- and monolayer graphene.

Quantum computers can outperform their classical counterparts at some tasks, but the full scope of their power is unclear. A new quantum algorithm hints at the possibility of far-reaching applications.