As you read this article, billions of transistors are switching electrical currents on and off inside your computer, generating heat in the process. This “heating problem” is the inevitable result of energy dissipation associated with electrons moving around, and it threatens to hinder further development of silicon-based computer technology. A possible solution to the problem is to make novel electronic devices that take advantage of each electron’s intrinsic magnetic moment (spin). In an insulator (as opposed to a metal or a semiconductor), it is possible to transport these spins without moving the electrons themselves, and in a device that uses spin currents instead of charge currents, energy dissipation would be greatly reduced, providing the much-desired pathway to increase computing power while avoiding the heating problem . But whereas charge currents can be induced easily using electric fields, an equivalent method of control does not exist for spin currents. Now Eric Parsonnet at the University of California, Berkeley, and his colleagues have taken an important step toward a spin-based computer by demonstrating a way to switch spin currents on and off electrically .
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