Volume 6 Issue 1, January 2010

Will Sesame Street, video games and robots get school children interested in science?

It is well established that protons and neutrons are bound states of quarks. Now magnetic excitations in systems of coupled spin chains are observed to consist of fractional constituent particles as well.

The Nernst effect is increasingly used to characterize a material's electronic structure. The discovery of an unexpected Nernst response in graphite establishes the role of dimensionality on this effect, and provides a means of distinguishing bulk and surface contributions to it.

Shockwaves driven by intense laser pulses allow the phase diagram of diamond to be extended up to pressures of 40 megabars and temperatures of 50,000 K. The results could help us better understand the material properties of the core of giant planets within and beyond our Solar System.

A method for measuring the excitation spectrum in atomic gases confined to optical lattices reveals the band structure of these systems, and should facilitate the comparison of quantum gas phases with their condensed-matter counterparts.

A simple programmable quantum processor has been created using trapped atomic ions. The system can be programmed with 15 classical inputs to produce any unitary operation on two qubits. This trapped-ion approach is amenable to scaling up for creating more complex circuits.

There is considerable debate over the size and direction of the non-adiabatic component of the spin-torque generated when a current flows across a domain wall in a ferromagnet. Measurements of this property in a wall just 1–10 nm wide suggest its value is small, arising from purely magnetic dissipation mechanisms.

The transition from a ferromagnetic to a paramagnetic state is observed directly as the density of carriers that mediate spin–spin coupling is varied. The measurement was performed on thin films of GaMnAs and was made possible by superconducting quantum interference devices (SQUIDS).

The Nernst effect—the generation of a transverse electric field in a system subject to a longitudinal temperature gradient and perpendicular magnetic field—is increasingly used as a probe of a material’s electronic structure. The discovery of an unexpected Nernst response in graphite establishes the role of dimensionality on this effect, and enables the individual contributions of bulk and surface to be distinguished.

Owing to the fact that graphene is just one atom thick, it has been suggested that it might be possible to control its properties by subjecting it to mechanical strain. New analysis indicates not only this, but that pseudomagnetic behaviour and even zero-field quantum Hall effects could be induced in graphene under realistic amounts of strain.

Gapless edge-state excitations known as one-dimensional chiral fermions explain many experimental observations of the behaviour of integer quantum Hall systems. But prevailing theory suggests the emergence of extra edge states as well. A new spectroscopic technique for probing the flow of energy in the edge channels of a quantum Hall device finds no loss of energy to such extra states.

Measurements of the melting point of diamond at pressures of around 10 million atm suggest it could be present in crystalline form in the interiors of giant planets. At even higher pressures and temperatures about 50,000 K, diamond melts to form an unexpectedly complex, polymer-like fluid phase.

Quantum oscillations in metals are a signature of electrons travelling in closed orbits in a magnetic field. Could such oscillations occur in the absence of closed orbits, as seems to be the case for the copper oxide superconductors that have arc-like segments instead of closed Fermi surfaces?

The composition of integral quantum number particles such as protons and neutrons from the strong confinement of fractional quantum number particles such as quarks is well known in high-energy physics. Now, similar behaviour has been found in condensed-matter physics, in the excitation spectra of a weakly coupled spin-ladder compound.

A spectroscopic technique that enables momentum-resolved probing of excitations of atomic gases in optical lattices allows the full band structure of such systems to be measured for the first time. The method should facilitate the comparison of quantum-gas phases with their condensed-matter counterparts.

In a glassy system, a distribution of relaxation times indicates a system that continues to rearrange itself. Besides the main relaxations involved in the glass transition, there are faster dynamics associated with secondary relaxations, which are predicted to reconfigure structures that are stringy rather than tightly clustered.

Intense optical beams can alter the way that a material interacts with X-ray radiation. This is now demonstrated by experiments that use femtosecond laser pulses to affect inner-shell processes in neon atoms, increasing the transmission of X-rays. This could allow imprinting of optical pulse trains onto much longer X-ray pulses.