IBM shows key step to spintronic transistors

August 14, 2012 // By Nick Flaherty
Researchers from IBM and ETH Zurich have directly mapped the formation of a persistent spin helix in a semiconductor, opening up a path to magnetic, spin-based switching and storage devices.

Until now, it was unclear whether or not electron spins possessed the capability to preserve the encoded information long enough before rotating. The scientists from IBM Research and the Solid State Physics Laboratory at ETH Zurich 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.
Using electrons is limited as the semiconductor dimensions continue to shrink to the point where the flow of electrons can no longer be controlled. Spintronics could surmount this approaching impasse by harnessing the spin of electrons instead of their charge. This new understanding in spintronics not only gives scientists unprecedented control over the magnetic movements inside devices but also opens new possibilities for creating more energy efficient electronics.
The researched showed how electron spins move tens of micrometers in a semiconductor with their orientations synchronously rotating along the path using 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 'waltz' of the electron spins in a GaAs device 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 microns, increasing the possibility to use the spin for processing logical operations, both fast and energy-efficiently.
Transferring spin electronics from the laboratory to the market still remains a major challenge