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 SDO sees partial eclipse in space
29.05.2017 | NASA/Goddard Space Flight Center

nachricht Strathclyde-led research develops world's highest gain high-power laser amplifier
29.05.2017 | University of Strathclyde

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: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

New insights into the ancestors of all complex life

29.05.2017 | Earth Sciences

New photocatalyst speeds up the conversion of carbon dioxide into chemical resources

29.05.2017 | Life Sciences

NASA's SDO sees partial eclipse in space

29.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>