COLLEGE
STATION, Feb. 7, 2005 – An international team of physicists
that includes a Texas A&M University professor has
announced discovery of a new spintronic effect in semiconductor
chips, the intrinsic spin Hall effect, which puts a
new twist on future technology and the possibility for
novel circuits with low energy consumption.
The team is formed by physicists Dr. Jörg Wunderlich
and Dr. Bernd Kaestner from the Hitachi Cambridge Laboratory,
U.K.; Prof. Tomás Jungwirth from the Institute
of Physics of the Academy of Sciences of the Czech Republic
and the University of Nottingham, U.K.; and Prof. Jairo
Sinova from Texas A&M.
In a normal Hall effect, a
voltage is created perpendicular to an electric current
as it flows through a conductor in a magnetic field.
The magnetic field deflects the moving charges to
the sides of the conductor, resulting in an observable
Hall voltage.
The spin Hall effect was first
predicted in 1971. Here the moving electrons, which
carry with them a tiny magnet called the "spin,"
collide with impurities and these collisions generate
opposing magnetizations at the conductor's edges.
Despite its intriguing ramifications,
the theory disappeared into virtual obscurity until
1999, when it was rediscovered and further elaborated.
Four years later, two independent teams, one including
Sinova and Jungwirth, proposed a novel mechanism called
the intrinsic spin Hall effect in which similar magnetization
occurs without the need for collisions.
The prediction touched off
a theoretical firestorm, resulting in more than 50
articles arguing for and against the possibility.
As the heated debate raged on, Wunderlich and Kaestner
developed a new type of device to measure magnetization
at each side of a high-mobility, ultra-thin conducting
layer embedded within a semiconductor chip using built-in
light-emitting diodes.
Armed with this novel tool,
Wunderlich and Kaestner teamed with Jungwirth and
Sinova to observe the spin Hall effect. Their findings
will be featured the February issue of Physics Today
along with an independent and parallel observation
of the effect in conventional bulk semiconductors.
Team members say the more than
10 times larger signal detected in the Hitachi device
can be attributed to the special layered design of
the semiconductor chip that yielded operation in a
regime close to the intrinsic spin Hall effect.
"They are both beautiful
experiments, and one of the most remarkable aspects
is that they seem to be exploring opposite regimes,"
Sinova adds.
The possibility of generating
magnetization without circulating currents has great
implications in many areas, most notably the design
of information processing and storage devices.
"Obviously we are only
at the beginning of this journey of discovery,"
Sinova explains. "As you gather more facts, the
truth tends to reveal itself. That's the fun of science.
We're seeking to know, and we're learning in the process."
For a full description of the work please see http://arxiv.org/abs/cond-mat/0410295;
to be published in February in Physical Review Letters
vol. 94 (2005)
For further information please
contact: Shana K. Hutchins, (979) 862-1237 or or Dr.
Jairo Sinova, (979) 845-4179 or sinova@physics.tamu.edu.
Contact: Keith Randall
kr@univrel.tamu.edu
979-845-4644
Texas A&M University
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