A NOVEL switch that manipulates electrons based on their spin rather than their charge could turn out to be one of the crucial building blocks in the next generation of spin-based electronics devices.

The quantum property of spin makes electrons act like magnets. The spin can be either "up" or "down", and a spin current is created from the movement of spin-up electrons in one direction and down electrons in the other.

In theory "spintronic" devices that exploit this effect should be much smaller than ordinary electronic devices. But so far spin currents have had to be controlled using powerful magnetic fields which are difficult to create in small electronic devices.

Now physicist David Awschalom and colleagues from the University of California at Santa Barbara have discovered a way to do it without magnetic fields (Science, DOI: 10.1126/science.1105514). They found that when a voltage drives electrons through a thin semiconductor channel, their movement produces a perpendicular flow of spin current across the channel.

As a consequence, spin accumulates at the edges of the semiconductor sample in what the team refer to as the "spin Hall effect". The result is a switch that turns the spin current on and off. The technique is "an important new pathway towards solid state spintronics", Awschalom says.