Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

33-year hunt for proof of spin current now over, announced in Science

12.11.2004


In a paper published online today in Science, a group of researchers led by David Awschalom, a professor of physics and electrical and computer engineering at the University of California, Santa Barbara, reports the observation of the spin Hall effect. This publication ends a 33-year long effort aimed at this discovery.

The Hall effect, named after American physicist Edwin Hall who discovered it in 1879, occurs when an electric current flows through a conductor in a magnetic field, creating a measurable transverse voltage. On a fundamental level, this effect originates because the magnetic field exerts a force on the moving charge carriers, which pushes them to one side of the conductor. The resulting buildup of charge at the sides of the conductor ultimately balances this magnetic field- induced force, producing a measurable voltage between opposite sides of the conductor.

In 1971, M.I. D’yakonov and V. I. Perel, two Russian physicists, predicted theoretically that a similar effect is expected in the realm of magnetization or spin physics. While the conventional Hall effect is widely used in today’s sensors and electronics, the spin Hall effect has defied experimental detection for 33 years. In analogy to its more conventional sibling, in the spin Hall effect, current-carrying electrons with opposite spins are predicted to move toward opposite sides of a semiconductor wire even without a magnetic field or magnetic materials.



This spin Hall effect results in the accumulation of spins at the edges of the sample with opposing spin polarization. In short, this phenomenon refers to the generation of a pure spin current transverse to an applied electric field: the flow of spin angular momentum with no net charge current.

Awschalom and his graduate students Yuichiro Kato and Roberto Myers, along with Art Gossard, a professor of materials and electrical and computer engineering, first discovered these signatures of the spin Hall effect in semiconductor chips made from gallium arsenide (GaAs), which is similar to those used in cell phones, and also studied the effect in samples made from indium gallium arsenide (InGaAs).

"We were initially skeptical when we first observed this in the laboratory," said Awschalom. "We kept asking ourselves why hadn’t anyone seen this earlier?" Kato agrees: "We thought it was just noise at first, but the peaks kept reproducing as the scans were repeated."

The research team constructed a Kerr microscope with 1-micrometer resolution that allowed them to clearly observe regions of electrons with opposite spins accumulated along the edges of the semiconductor chips. Because no net charge was flowing, attempts to see the spin Hall effect using electronic detectors have been problematic. Some of the experiments carried out at UCSB ran for nearly 30 continuous hours, requiring the researchers to carefully control the laboratory environment and the experimental conditions for data collection.

The potential applications of this discovery are numerous and may include sensing technologies, potential pathways towards shuttling spin information in semiconductors as well as quantum computing and quantum communication, according to Awschalom. "The most exciting aspect of this finding is that you don’t know exactly where it’s going to lead," he said. This research was funded in part by the Defense Advanced Research Projects Agency and the National Science Foundation.

At UCSB, Awschalom is director of the Center for Spintronics and Quantum Computation, and is associate scientific director of the California Nanosystems Institute.

Awschalom joined the University of California, Santa Barbara as a professor of physics in 1991. His research has been chronicled in his more than 250 scientific journal articles, and has also been featured in the New York Times, the Wall Street Journal, the San Francisco Chronicle, the Dallas Morning News, Discover magazine, Scientific American, Physics World, and New Scientist. His research focuses on optical and magnetic interactions in semiconductor quantum structures, spin dynamics and coherence in condensed matter systems, macroscopic quantum phenomena in nanometer-scale magnets, and quantum information processing in the solid state.

Awschalom’s honors include the IBM Outstanding Innovation Award, the Outstanding Investigator Prize from the Materials Research Society, the International Union of Pure and Applied Physics (IUPAP) Magnetism Prize, and the 2005 Oliver E. Buckley Prize from the American Physical Society.

Barbara Bronson Gray | EurekAlert!
Further information:
http://www.ucsb.edu
http://www.sciencexpress.org/

More articles from Physics and Astronomy:

nachricht NASA detects solar flare pulses at Sun and Earth
17.11.2017 | NASA/Goddard Space Flight Center

nachricht Pluto's hydrocarbon haze keeps dwarf planet colder than expected
16.11.2017 | University of California - Santa Cruz

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>