A team of researchers at MIT have created a new method based on spintronics to study the characteristics of electrons. This method is used to analyze the electrons in a solid material to determine various combinations of energy, momentum and the spin of these electrons.
"This diagram illustrates how lasers can be used to control an electric current on these new materials. Electrons (blue spheres) travel, as if on a highway, in different directions, with their axis of spin (arrows) aligned differently according to the direction of travel. A circularly polarized laser beam (left) affects only electrons going in one direction, removing them from the flow, leaving a net flow — an electric current — going the other way. Photo: Gedik Group "
The conventional method involved a very slow process of rotating the material while light was focused upon it. This ejects the electrons from the solid hence the combination of energy, momentum and spin of the electrons are measured. However, this approach provides only data at a particular point and not a three- dimensional picture as the new method.
The new method uses pulses of circular polarized laser light, which can be measured precisely and a three-dimensional view of the electron behaviour can be easily captured. This has enabled researchers to analyse the electron behaviour in different directions, which is fundamental to the understanding of the materials properties. This new method helps with the understanding of the materials properties in a far lesser time. This method also revealed that the direction of the electrons spin motion is not perpendicular to the electron’s motion and at higher energies a slight tilt was observed.
Ideally this method was primarily devised to study the behaviour of topological insulators that have unique properties wherein their surfaces proved to be an effective electrical conductor where as the three-dimensional bulk of the material acts like an insulator. This method has applications in the study of magnets and superconductive materials. In capturing the electron’s spin movements can lead to their effective management of the spin circuits that can carry data rather than electric charge.
Source: http://www.web.mit.edu