Computers may soon be able to recycle part of their own waste heat,
using a material being studied by researchers.The material is a
semiconductor called gallium manganese arsenide.
Researchers at the Ohio State University describe the detection of an
effect that converts heat into a quantum mechanical phenomenon -- known
as spin -- in a semiconductor.Once developed, the effect could enable
integrated circuits that run on heat, rather than electricity.This
research merges two cutting-edge technologies: thermo-electricity and
spintronics, explained team leaders Joseph Heremans, Ohio Eminent
Scholar in Nanotechnology, and Roberto Myers of the Ohio State
University.Myers and Heremans have been trying to combine spintronics
with thermo-electronics -- that is, devices that convert heat to
electricity.
“Spintronics is considered as a possible basis for new computers in
part because the technology is claimed to produce no heat. Our
measurements shed light on the thermodynamics of spintronics, and may
help address the validity of this claim,” Nature quoted Heremans as
saying.In one possible use of thermo-spintronics, a device could sit
atop a traditional microprocessor, and siphon waste heat away to run
additional memory or computation.The researchers studied how heat can be
converted to spin polarization-an effect called the spin-Seebeck
effect. Researchers at Tohoku University first identified it.
Those
researchers detected the effect in a piece of metal, rather than a
semiconductor.The new measurements, carried out by team member
Christopher Jaworski have provided the first independent verification of
the effect in a semiconductor material called gallium manganese
arsenide. Samples of this material were carefully prepared into thin
single-crystal films by collaborators Shawn Mack and David Awschalom at
the University of California, who also assisted with interpretation of
the results.
In the experiment, they heated one side of the sample, and
then measured the orientations of spins on the hot side and the cool
side. On the hot side, the electrons were oriented in the spin-up
direction, and on the cool side, they were spin-down.The researchers
also discovered, to their own surprise, that two pieces of the material
do not need to be physically connected for the effect to propagate from
one to the other.
“We figured that each piece would have its own distribution of
spin-up and spin-down electrons.
“Instead, one side of the first piece was spin up, and the far side
of the second piece was spin down. The effect somehow crossed the gap,”
said Myers.Despite these new experiments, the origin of the spin-Seebeck
effect remains a mystery.The findings were published in the journal
Nature Materials.
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