Spin transistor

IN AN earlier article (The Hindu, April 21, 01) the history of the development of electron spin was traced. In the issue of New Scientist (16 June 2001), two recent developments employing this technique have been reported: a battery that can store electron spin and release it on demand and a new device, ``spin transistor''.

Shuffling groups of electronic charges around a semiconductor circuit has been the traditional technology for the construction of semi- conductor devices. But electrons also spin, producing a magnetic field like a tiny bar magnet.Researchers at the University of California, Santa Barbara and the University of Iowa have developed the ideas further.

If the spin axes of all the electrons in a group are aligned, the phenomenon of spin polarisation occurs and further it shows stability.

The group exhibits another property that was really not expected: the spin-up can correspond to the Os and the spin-down to the 1s of digital electronics.

``Controlling the flow of spin-polarised electrons paves the way for building the new device, which could combine current complification with the ability to remember data when the power is turned off.

One of the most exciting possible applications is in quantum computers, which will use the quantum uncertainty of electron spins to process data at superfast speeds''. The may prove to be a key step in integrating smaller and faster devices into the computer-chips.

R. Parthasarathy

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