Spinning new theory on particle spin brings science
closer to quantum computing
Argonne, NIU physicists develop potentially groundbreaking
approach
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ARGONNE, Ill. (Sept. 7, 2006) – Physicists at the U.S. Department of Energy's
Argonne National Laboratory have devised a potentially groundbreaking theory
demonstrating how to control the spin of particles without using superconducting
magnets — a development that could advance the field of spintronics and bring
scientists a step closer to quantum computing.
Spintronics, also known as spin electronics, is an emerging technology that
looks to develop devices that exploit the quirky world of quantum physics,
or physics at the incredibly small atomic level, particularly the up-or-down
spin property of electrons. Conventional electronics use the charge of the
electron. Spintronic devices would use both the spin and charge, achieving
new functionality.
Scientists across the globe are racing to develop the spintronics field. It
could revolutionize the computing industry with chips that are more versatile
and exponentially more powerful than today's most cutting-edge technology.
Physicists Dimitrie Culcer and Roland Winkler, along with Christian Lechner
of Regensburg
University, Germany, will publish their theoretical findings
in the Sept. 8 issue of Physical Review Letters. Culcer and Winkler
are at Northern Illinois
University, in addition to their affiliation with
the Advanced Photon Source at Argonne.
“Our research illuminates a new pathway for generating and manipulating the
spin in semiconductors,” Winkler said. “This is important, because the use
of bulky superconducting magnets would be impractical in most devices.”
The physicists theorize that spin can be induced and manipulated by running
a current through gallium arsenide, a common semiconductor, in what is known
as spin-3/2 hole systems, which previously have been little studied. Hole systems
are “missing electrons,” while the fraction 3/2 refers to the magnitude of
the spin. Spin-3/2 hole systems are created in semiconductors by “doping” — introducing
impurities that have one less electron compared to the host material.
Geometry also must play a crucial role in spin manipulation, according to
the researchers. They propose development of a nano-sized and L-shaped device
that allows for the exploitation of the newly discovered effects in spin-3/2
hole systems.
“Spin polarization is achieved as the current flows around the corner,” Winkler
said.
“We believe we've discovered a much simpler way for inducing spin polarization,” he
added. “We don't need a big magnet. The only requirement in our case is an
electrical current in the sample, which is much easier to achieve than putting
the sample in a magnetic coil. For an electrical current, you only need two
contacts.”
Culcer said the researchers hope the publication will raise awareness of new
and exciting physics that can be accomplished in spin-3/2 hole systems.
“We do basic research and do not work directly on information technology,” Culcer
said. “But researchers working on quantum computing are primarily interested
in spin systems. For the past 50 years, scientists have intensely studied what's
known as spin-1/2 systems.
“One of our primary goals with this paper was to demonstrate what could be
accomplished with spin-3/2 systems,” he said. “We hope to point scientists
in a direction that offers the possibility of new applications and hopefully
ways of manipulating information in the future.”
Argonne National Laboratory seeks solutions to pressing national problems in science and technology.
The nation's first national laboratory, Argonne conducts leading-edge basic
and applied scientific research in virtually every scientific discipline. Argonne
researchers work closely with researchers from hundreds of companies, universities,
and federal, state and municipal agencies to help them solve their specific
problems, advance America 's scientific leadership and prepare the nation for
a better future. With employees from more than 60 nations, Argonne is managed
by UChicago
Argonne, LLC for
the U.S.
Department of Energy's Office
of Science.
For more information, please
contact Steve McGregor (630/252-5580 or media@anl.gov)
at Argonne.
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