IBM observes spintronic 'waltz'

LONDON – Researchers from IBM Research and the university ETH, both based in Zurich, have reported the observation of a persistent spin helix in a semiconductor, which they claim could have implications for information storage and processing.

The research team has reported how they observed that synchronized electron spins move tens of micrometers in a semiconductor with the spin orientation precessing about the path similar to a couple dancing the waltz, IBM said. In addition, the synchronization of the electrons as they travel though a semiconductor lattice can extend the lifetime of the electron spin coordination by a factor of 30 to 1.1 nanoseconds.

It is hoped that the use of electron spin rather than electronic charge as a fundamental aspect of data storage and processing could overcome limitations that are fast approaching due to diminishing device dimensions.

Gian Salis, of the Physics of Nanoscale Systems research group at IBM Research Zurich, said: "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. 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 concept of locking electron spin rotation was proposed in 2003 and since that time some experiments have even found indications of such locking, but until now it had never been directly observed.

The team used spin-orbit interaction to obtain the synchronization and short laser pulses to monitor thousands of electron spins. Typically such spins would rotate randomly and loose orientation. The scientists were able to observe how the spins arrange neatly into a regular stripe-like pattern, the so-called persistent spin helix.

The experiment was performed in ultra-clean and precise engineered gallium arsenide supplied by ETH Zurich.

There are still numerous barriers to transferring spintronic research to the market, not least that spintronic research usually has to be conducted at low temperatures to minimize interactions between the electron spin and the surrounding environment. In the case of this particular research IBM scientists worked at 40 Kelvin (-233 C, -387 F).

The scientific paper entitled "Direct mapping of the formation of a persistent spin helix" by M.P. Walser, C. Reichl, W. Wegscheider and G. Salis was published online in Nature Physics, DOI 10.1038/NPHYS2383 on Aug. 12, 2012.


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