Magnetic current flows solo

Peter Weiss

Besides possessing an electric charge, every electron totes around a tiny magnetic field that points either up or down. The particle's magnetism arises from a quantum mechanical property called spin. Now, an international team of physicists has induced spins to flow without an accompanying flow of charge.

That feat could prove important to the burgeoning field of spintronics, which aims to control spin currents much as the field of electronics controls charge currents, says Henry M. van Driel of the University of Toronto (SN: 2/22/03, p. 118: Available to subscribers at http://www.sciencenews.org/articles/20030222/fob7.asp).

To achieve pure spin flow, van Driel and his colleagues simultaneously trained pulses from two lasers—one at twice the frequency of the other—onto a semiconductor. This input prompted some up-spin electrons to flow within the semiconductor in the opposite direction, yet at the same rate, as some down-spin electrons.

Because the electrons had like charges but opposite paths, the charge currents canceled out. However, the spin currents enhanced each other because they were of opposite polarity and direction, van Driel says. So, in the final analysis, only spin took a spin.

The scientists describe their experiments in the April 4 and May 30 Physical Review Letters.

********

References:

Hübner, J. … and H.M. van Driel. 2003. Direct observation of optically injected spin-polarized currents in semiconductors. Physical Review Letters 90(May 30):216601.

Stevens, M.J. …and H.M. van Driel. 2003. Quantum interference control of ballistic pure spin currents in semiconductors. Physical Review Letters 90(April 4):136603.

Further Readings:

Weiss, P. 2003. Electronic acrobats: Tidily tweaking electrons twirls. Science News 163(Feb. 22):118. Available to subscribers at http://www.sciencenews.org/articles/20030222/fob7.asp.

Sources:

Henry M. van Driel
Department of Physics
University of Toronto
60 St. George Street
Toronto, ON M5S 1A7
Canada

From Science News, Volume 164, No. 1, July 5, 2003, p. 14.