IBM scientists say they’ve made a big leap towards the practical use of spintronic computing with the first-ever direct mapping of the formation of a persistent spin helix in a semiconductor.
Spintronics uses the spin of electrons, rather than their charge, to store information, and promises vastly more efficient electronic devices. Unfortunately, though, nobody’s been quite sure that electron spins could actually preserve encoded information for long enough before rotating – until now.
The IBM/ETH Zurich team has now shown that synchronizing electrons extends the spin lifetime of the electron by 30 times, up to 1.1 nanoseconds – the same time it takes for an existing 1 GHz processor to cycle.
The acievement’s based on a previously unknown aspect of physics, whereby electron spins move tens of micrometers in a semiconductor with their orientations synchronously rotating along the path – similar to a couple dancing the waltz, says IBM.
“If all couples start with the women facing north, after a while the rotating pairs are oriented in different directions. We can now lock the rotation speed of the dancers to the direction they move,” explains IBM’s Dr Gian Salis.
“This results in a perfect choreography where all the women in a certain area face the same direction. This control and ability to manipulate and observe the spin is an important step in the development of spin-based transistors that are electrically programmable.”
The team used ultra-short laser pulses to monitor the evolution of thousands of electron spins that were created simultaneously in a very small spot. And where such spins would usually rotate randomly and quickly lose their orientation, they can now arrange neatly into a regular stripe-like pattern – the so-called persistent spin helix.
It’s the first time such locking has ever been directly observed.
The scientists imaged the synchronous ‘waltz’ 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.
Transferring spin electronics from the laboratory to the market will still be quite a challenge; currently, the effect shows up only at very low temperatures, 40 Kelvin in this case.