Pure spin currents

Article By:

Hoffmann, Axel Materials Science Division, Argonnne National Laboratory, Lemont, Illinois.

Last reviewed:2010

DOI:https://doi.org/10.1036/1097-8542.YB100184

Modern information technologies are based on semiconducting electronic devices, such as the silicon transistor in a computer's central processing unit (CPU), where information is encoded by electric charges and transmitted via charge currents carried by electrons or holes (missing electrons). Since the late 1960s, in accordance with the observation that has become known as Moore's law, semiconducting devices have continued to miniaturize in size, increase in speed, and decrease in cost. Today, a CPU can contain billions of transistors. However, a significant obstacle to this continued downscaling is power dissipation. As individual devices become smaller and the packing density increases, the amount of undesirable heat dissipation becomes increasingly problematic. In fact, the dissipated power density inside modern microprocessors (100 W/cm²) is nowadays becoming comparable to the power density within a nuclear power reactor (based on the volume of the reactor pool). The difference, of course, is that the active volume of a processor chip is miniscule compared to that of a reactor, so the total power dissipations are vastly different, while the power densities are not.

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