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Friday, 29 July 2011

An Unexpected Clue to Thermopower Efficiency

Lawrence Berkeley National Laboratory (LBNL)
July 28, 2011

Lawrence Berkeley National Laboratory scientists and their colleagues have discovered a new relation among electric and magnetic fields and differences in temperature, which may lead to more efficient thermoelectric devices that convert heat into electricity or electricity into heat.

“In the search for new sources of energy, thermopower – the ability to convert temperature differences directly into electricity without wasteful intervening steps – is tremendously promising,” says Junqiao Wu of Berkeley Lab’s Materials Sciences Division (MSD), who led the research team. Wu is also a professor of materials science and engineering at the University of California at Berkeley. “But the new effect we’ve discovered has been overlooked by the thermopower community, and can greatly affect the efficiency of thermopower and other devices.”

Wu and his colleagues found that temperature gradients in semiconductors, when one side of the device is hotter than the opposite side, can produce electronic vortices – whirlpools of electric current – and can, at the same time, create magnetic fields at right angles to both the plane of the swirling electric currents and the direction of the heat gradient. The researchers report their results in Physical Review B.
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