The illustration depicts the characteristic spin orientation (arrows) of electrons in a topological insulator (below). Using an initial circular polarised laser pulse, the spins are excited and point up or down. This can be proven by a second linearly polarised laser pulse (above). Credit: HZB
Scientists have shown how spin-polarized currents can be initiated in a controlled manner within samples of topological insulator material. In addition, they were able to manipulate the orientation of the spins of these currents. They thereby demonstrated that this class of materials is suitable for data processing based on spin.
Future information technologies should employ considerably less energy for processing data via topological insulators (with electrons at the surface being extremely mobile, while the bulk material within is an insulator). Since electrons also simultaneously carry a magnetic moment (spin), topological insulators might also make “spintronic” components feasible (based on transport or manipulation of their spins instead of electrons).
A team investigated samples of antimony-telluride, a topological insulator, using circularly polarised laser light. They were able to initiate and direct currents of electrons whose spins were oriented in parallel (i. e., spin-polarised currents) using the “rotational direction” of the laser light. In addition, they were successful in changing the orientation of the spins as well.
“If you were to utilise magnetically doped topological insulators, you could also probably store this spin information,” explains Oliver Rader, who heads the research group for green spintronics at HZB. “To investigate this however, and also be able to explore the dynamic behaviour of the magnetic moments in particular, ultra-short light pulses in the soft Xray region are needed. These kinds of experiments can become standard with the planned upgrade of the BESSY II synchrotron source to BESSY-VSR,” he hopes. http://www.helmholtz-berlin.de/pubbin/news_seite?nid=14443&sprache=en&typoid=1
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