A team of researchers from the University of Cincinnati have achieved control of the spin of electrons traveling on a wire by simply regulating an electrical voltage. This is a major milestone in the brief history of spintronics, the emerging technology that uses the spin of electrons to store and manipulate digital information with much higher speeds and efficiency.
Electronic devices use the electrical charge of electrons to process and store information. While technically easy to achieve and apt to miniaturization up to the nanoscale level, researchers have long realized that speed and energy efficiency of classical electronics can only be pushed to a certain limit.
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Spintronics is an alternative approach that represents bits with the spin of an electron, rather than its charge — so, for instance, an electron with "up" spin could represent a "1" and one with a "down" spin could represent a "0". While technologically harder to achieve, this approach reduces heat dissipation to a minimum and can support much higher speeds: for these reasons, many researchers agree that spintronics could be the next big thing in digital information processing.
Because a spinning electrically charged particle like an electron has well-known magnetic properties, the most natural way to control electronic spin is to use ferromagnetic materials embedded in spintronic devices. This, however, makes the devices very bulky, which is clearly the opposite of the direction towards which technological progress is pushing.
Led by Dr. Debray, the UC team managed to control the spin of electrons traveling on a wire with an all-electrical device for the very first time, reaching a milestone in this new and very promising field that is important mainly because it allows for much smaller spintronic devices to be built.
The team used an indium arsenide "quantum point contact," a wire only a few hundred nanometers in length whose conductivity can be modified by regulating the voltages at its two ends. The asymmetry that comes from setting two different voltages at the two ends (gates) allows the electrons to become polarized as they enter the wire.
Even though this is a major advancement, a number of issues still need to tackled — the main of which being that the mechanism currently works only at very low temperatures. The next step would therefore be to achieve the same results at a higher temperatures, perhaps using a different material such as gallium arsenide.
The team's findings were funded by the National Science Foundation and published on a recent issue of Nature Nanotechnology.