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's Fermi catches gamma-ray flashes from tropical storms
25.04.2017 | NASA/Goddard Space Flight Center

nachricht DGIST develops 20 times faster biosensor
24.04.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)

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: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>