Magazine article Science News

Pumping Electrons: Look Ma! No Heat!

Magazine article Science News

Pumping Electrons: Look Ma! No Heat!

Article excerpt

Heat buildup has always plagued electric circuits. As electronic components continue to shrink, even small amounts of heat become troublesome. Now, scientists have developed a way of pumping electrons through tiny circuits that may eliminate the dissipation of energy as damaging heat.

"This is a new means of making charge move," says Charles M. Marcus of Stanford University, who led the research. To make their pump, he and his team have used an existing method of making a device known as a quantum dot (SN: 4/11/98, p. 236). The dot confines electrons to a region within a thin layer of a semiconductor or metal.

To move electrons through their pump, the scientists manipulate the wave properties of electrons within the dot. By exploiting those properties, the researchers control current completely via the principles of quantum mechanics--the physics of the smallest bits of matter.

"I think this experiment is very significant," comments Qian Niu of the University of Texas at Austin. "It is really the first experiment that demonstrates that you can use a pure quantum effect to pump electrons." He and David J. Thouless of the University of Washington in Seattle formulated theories in the 1980s and early 1990s that indicated the feasibility of such quantum pumping.

In previous experiments, scientists have created electron pumps from quantum dots or other electron-confining structures. However, they have always relied to some extent on a classical-physics effect, the mutual electrostatic repulsion of electrons, to control flows in and out of the device. …

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