Volume 4 Issue 3, March 2008

The electron is responsible for charge and spin transport in conventional metals. In contrast, the existence of well-defined electronic excitations in the metallic state of high-temperature superconductors is highly debated.

A more comprehensive understanding of coupled quantum systems could soon be in reach with a capacitance-based scanning probe technique that explores the behaviour and interaction of individual dopant atoms in a semiconductor.

Sophocles had it right, the Rolling Stones made a friendly amendment and Linus Pauling detailed the conceptual mechanism for finding novel materials that will define and revolutionize the future.

Numerous experiments on cuprate materials suggest that a zero-temperature phase transition is hidden beneath the superconducting dome. Is it the key to understanding high-temperature superconductivity, and can it explain the anomalous normal state properties?

Quantum magnetism describes systems of magnetic spins in which quantum mechanical effects dominate, often in surprising ways. This review article covers phase transitions between these states, including quantum criticality and entangled electron states.

At a zero-temperature phase transition from one ordered state to another, fluctuations between the two states lead to quantum critical behaviour that can lead to unexpected physics. Metals with ‘heavy’ electrons often harbour such weird states.

A collection of bosonic particles, such as liquid helium or ultracold gases, can condense into a ground state in which the atoms flow as a ‘superfluid’ without scattering. Magnetic materials further illustrate the generality of the effect, as described in this review.

The propagation of charge carriers in graphene under an imposed periodic potential can become strongly anisotropic, suggesting a way of making electronic circuits with appropriately patterned surface electrodes without the need for cutting nanoscale structure into graphene.

For the first time, a purely dipolar quantum gas has been prepared experimentally. Different regimes have been explored; in some, the gas is stable, whereas in others it collapses due to the strong dipole–dipole interaction between the constituent atoms.

Mixing two different types of grains in a revolving tumbler produces several radial streaks as the grains segregate. Unexpectedly though, after hundreds of revolutions, only one streak remains.

Our tools for understanding phase transitions at thermal equilibrium do not usually apply to granular matter. However, a vibrating quasi-one-dimensional system displays dynamic behaviour common to classic phase transitions.

How to look good on a budget.

Phase transitions are familiar occurrences, such as the freezing of water to ice. When the transition occurs at zero temperature, it is known as a 'quantum phase transition'. As distinct states of matter coexist at a transition, there are quantum fluctuations between them. This Focus explores the resulting – and often surprising – collective behaviour.