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September 26, 2007

Spintronics: Quantum spin hall effect could be future of computers

Stanford physics Professor Shoucheng Zhang says a new generation of semiconductors, designed around the phenomenon known as the Quantum Spin Hall Effect, could keep Moore's law in force for decades to come.

Using special semiconductor material made from layers of mercury telluride and cadmium telluride, the experimenters employed quantum tricks to align the spin of electrons like a parade of tops spinning together. Under these extraordinary conditions, the current flows only along the edges of the sheet of semiconductor.

The electrons' strange behavior constitutes a new state of matter, Zhang said, joining the three states familiar to high school science students—solids, liquids, gases—as well as more unworldly states such as superconductors, where electrons flow with no resistance. He describes the quest for new states of matter as the holy grail of condensed matter physics.

Similar effects have been demonstrated before, but only at extremely cold temperatures and under the effects of powerful magnetic fields—conditions that cannot exist inside the common computer. "What we managed to do is basically get rid of the magnetic field," Zhang said.

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