Image: IBM scientists Matthias Walser (left) and Gian Salis who published the finding with C. Reichl and W. Wegscheider from ETH Zurich in Nature Physics © IBM/ETH Zurich
Aiming to use electron spins for storing, transporting and processing information, researchers from IBM (NYSE: IBM) and scientists at ETH Zurich in Switzerland revealed the first-ever direct mapping of the formation of a persistent spin helix in a semiconductor. Until now, it was unclear whether or not electron spins possessed the capability to preserve the encoded information long enough before rotating. The scientists demonstrated that synchronizing electrons extends the spin lifetime of the electron by 30 times to 1.1 nanoseconds – the same time it takes for an existing 1 GHz processor to cycle. IBM scientists used ultra short laser pulses to monitor the evolution of thousands of electron spins that were created simultaneously in a very small spot. Atypically, where such spins would randomly rotate and quickly loose their orientation, for the first time, the scientists could observe how these spins arrange neatly into a regular stripe-like pattern, the so-called persistent spin helix. The concept of locking the spin rotation was originally proposed in theory back in 2003 and since that time some experiments have even found indications of such locking, but until now it had never been directly observed. IBM scientists imaged the synchronous 'walt' of the electron spins by using a time-resolved scanning microscope technique. The synchronization of the electron spin rotation made it possible to observe the spins travel for more than 10 micrometers or one-hundredth of a millimeter, increasing the possibility to use the spin for processing logical operations, both fast and energy-efficiently. The reason for the synchronous spin motion is a carefully engineered spin-orbit interaction, a physical mechanism that couples the spin with the motion of the electron. The semiconductor material called gallium arsenide (GaAs) was produced by scientists at ETH Zurich. GaAs is a III/V semiconductor commonly used in the manufacture of devices such as integrated circuits, infrared light-emitting diodes and highly efficient solar cells. Transferring spin electronics from the laboratory to the market still remains a major challenge. Spintronics research takes place at very low temperatures at which electron spins interact minimally with the environment. In the case of this particular research IBM scientists worked at 40 Kelvin (-233° C, -387° F).
M. P. Walser, C. Reichl, W. Wegscheider, G. Salis: Direct mapping of the formation of a persistent spin helix, In: Nature Physics AOP, August 12, 2012, DOI:10.1038/ nphys2383:
http://dx.doi.org/10.1038/nphys2383
http://www.theregister.co.uk/2012/08/13/ibm_lockstep_spinning/
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