Volume 8 Issue 10, October 2012

Faraday and Dirac constructed magnetic monopoles using the practical and mathematical tools available to them. Now physicists have engineered effective monopoles by combining modern optics with nanotechnology. Part matter and part light, these magnetic monopoles travel at unprecedented speeds.

Devices based on surface electrons in topological insulators are keenly anticipated, but singling these electrons out amid abundant bulk electrons poses a formidable challenge. Inspiration from the common transistor now enables manipulation of these exotic states.

Interfacial instabilities brought on by the penetration of one fluid into another hamper processes such as enhanced oil recovery from porous rock. But these instabilities can be suppressed with a simple gradient in fluid depth — a natural feature of many practical vessel geometries.

Optical vortices usually break up when they propagate through nonlinear media. Now, however, experiments show the helical structure of an infrared beam can survive a high-harmonic-generation process. This could lead to a table-top source of attosecond helical light pulses.

The magnetic states found in iron-based superconductors are more complex than originally thought. This Review argues that the magnetism arises from both itinerant and localized electrons.

Shor’s quantum algorithm factorizes integers, and implementing this is a benchmark test in the early development of quantum processors. Researchers now demonstrate this important test in a solid-state system: a circuit made up of four superconducting qubits factorizes the number 15.

An analogue of a magnetic monopole is now observed in a condensed state of light–matter hybrid particles known as cavity polaritons. Spin-phase excitations of the polariton fluid are accelerated along the cavity under the influence of a magnetic field—just as if they were single magnetic charges.

Doping a topological insulator with manganese makes it magnetic. Moreover, decreasing the concentration of Dirac fermions in a Mn-doped topological insulator with an electric field increases the strength of its magnetic characteristics—a trait that could be valuable to the use of topological insulators in the development of spintronics.

Chirality is usually manifested by differences in a material’s response to left- and right-circularly polarized light. This difference is the result of the specific distribution of charge within chiral materials. A similar response has now been found to result from the chiral spin structure of an antiferromagnet.

It is known that graphene exhibits natural ripples with characteristic lengths of around 10 nm. But when it is stretched across nanometre-scale trenches that form in a reconstructed copper surface, it develops even tighter corrugations that cannot be explained by continuum theory.

Optical vortices exhibit a corkscrew-like shape as they travel. The study of this phenomenon, known as singular optics, is now extended to the high-power regime where high-harmonic processes become evident. This type of radiation could help illuminate novel attosecond phenomena in atoms and molecules.

When a low-viscosity fluid penetrates a fluid of higher viscosity confined by parallel plates, finger-like patterns propagate at the interface between the two fluids. Experiments now show that tapering the fluid cell can suppress this instability - providing interfacial control via a simple change in geometry.

Decreasing the doping of a cuprate superconductor below a certain critical value causes its critical temperature to fall, however the reason for this has been unclear. Sensitive measurements of the Nernst effect in yttrium barium copper oxide suggest it is the result of competition with an emerging stripe phase.

Spin–orbit interaction induces spin-polarization decay in semiconductor quantum wells. But this decay can be suppressed in favour of a helical spin mode by tuning the interaction. Optical pump–probe measurements provide direct evidence of the resulting helix—a signature that has so far only been inferred from transport measurements.

When electrons are accelerated to near light-speeds through an overdense plasma by an intense laser beam, the usually opaque plasma becomes optically transparent. High-speed laser experiments provide unprecedented insight into the dynamics of this process.