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In this issue:
Exotic Material Could Revolutionize Electronics
Colloquium Today: LCLS Commissioning

SLAC Today

Monday - June 15, 2009

Exotic Material Could Revolutionize Electronics

(Image - electron band structure diagram)
Surface electron band structure of bismuth telluride. (Image courtesy of Yulin Chen and Z. X. Shen.)

Move over, silicon—it may be time to give the Valley a new name. Physicists at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University have confirmed the existence of a type of material that could one day provide dramatically faster, more efficient computer chips.

Recently-predicted and much-sought, the material allows electrons on its surface to travel with no loss of energy at room temperatures and can be fabricated using existing semiconductor technologies. Such material could provide a leap in microchip speeds, and even become the bedrock of an entirely new kind of computing industry based on spintronics, the next evolution of electronics.

Physicists Yulin Chen, Zhi-Xun Shen and their colleagues tested the behavior of electrons in the compound bismuth telluride. The results, published online June 11 in Science Express, show a clear signature of what is called a topological insulator, a material that enables the free flow of electrons across its surface with no loss of energy.

The discovery was the result of teamwork between theoretical and experimental physicists at the Stanford Institute for Materials & Energy Science, a joint SLAC-Stanford institute. In recent months, SIMES theorist Shoucheng Zhang and colleagues predicted that several bismuth and antimony compounds would act as topological insulators at room-temperature. The new paper confirms that prediction in bismuth telluride. "The working style of SIMES is perfect," Chen said. "Theorists, experimentalists, and sample growers can collaborate in a broad sense."

The experimenters examined bismuth telluride samples using X-rays from the Stanford Synchrotron Radiation Lightsource at SLAC and the Advanced Light Source at Lawrence Berkeley National Laboratory. When Chen and his colleagues investigated the electrons' behavior, they saw the clear signature of a topological insulator. Not only that, the group discovered that the reality of bismuth telluride was even better than theory.  Read more...

Colloquium Today: LCLS Commissioning

(Image - SLAC Colloquium banner)

The Linac Coherent Light Source is a self-amplified spontaneous emission 1.5-15 Angstrom X-ray Free-Electron Laser, or FEL, driven by the final third of the SLAC linac. The facility is presently in an advanced phase of commissioning. The injector, linac and new bunch compressors were commissioned in 2007 and 2008, establishing the necessary electron beam brightness. The final phase of commissioning began in November 2008, with first FEL light achieved in mid-April 2009.

In today's colloquium, SLAC head of LCLS accelerator physics Paul Emma will report on the facility's current accelerator, undulator and FEL operations. His talk will begin at 4:15 p.m. in Panofsky Auditorium. The colloquium is free and open to all.

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