Spin doctors

Physics professor Ali Yazdani runs a lab that literally floats on air.

Deep within the basement of Jadwin Hall, powerful air pistons prop up a 35-ton room, protecting a scanning tunneling microscope from miniscule vibrations caused by seismic activity and the traffic from Washington Road. The microscope is so sensitive that it needs specialized shields to protect it from local radio station signals.

The sensitivity isn't for nothing. Using this technology, Yazdani and his group have developed an innovative method to arrange manganese atoms along a gallium arsenide surface — an obscure-sounding advance that may revolutionize the way computers work.

The epiphany came early one morning in December 2004, as Yazdani and graduate students Dale Kitchen and Anthony Richardella were testing an imaging method at the University of Illinois at Urbana-Champaign.

"We had absolutely no idea what we were doing," said Yazdani, who came to the University last year.

The group had spent several long and sometimes frustrating months using the microscope to image individual manganese atoms. They had begun to develop a complicated theory describing the behavior of the manganese atoms but stopped short of publishing it because something didn't seem right. "We had a gut feeling that something was fishy," Yazdani said. "It felt wrong but we were going along with it because we didn't have any better ideas."

It turns out that the gut feeling was right, as Kitchen and Richardella soon discovered what was really happening. The microscope that was being used to image the manganese atoms was actually pushing each one into the gallium arsenide surface by swapping it with a gallium atom on the top layer.

This surprising finding rallied the researchers to develop a technique that allowed them to position manganese atoms in precise arrangements across the surface and observe the quantum mechanical interactions between nearby atoms. The results, which were published in the July 27 issue of the prestigious journal Nature, are a major advance in semiconductor spintronics, a field that aims to integrate the semiconductor technology of computer chips and the magnetic properties of hard drive storage into a single, unified component.

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While Yazdani — who worked at IBM and the University of Illinois after receiving his doctorate from Stanford — is most interested in the basic science of quantum spin interactions, he acknowledges the potential of his findings for the field of computer engineering.

Traditionally, computers have used two separate components: silicon chips for computation and magnetic material for hard disk storage. By precisely placing manganese atoms, which are magnetic, into the semiconducting gallium arsenide surface, Yazdani has set the groundwork for a new type of chip in which the interaction of quantum spins can perform both computation and storage.

Such technology would result in lower energy and size requirements for computer hardware. It also offers the tantalizing prospect of massively parallel computing, which could be used to solve previously intractable problems in mathematics.

While the development of usable spintronics technology is seen by many as a distant, if not impossible, goal, Yazdani is not ruling anything out. "People are pretty clever," he said. Future semiconductors "could be controlled in ways which would boggle the mind."

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Yazdani, who came to the United States from his native Iran when he was 15 years old, said he loves his job, often finding himself in the lab until midnight.

"You work at the edge of what's possible, which means that 90 percent of the time it doesn't work," he said. But as long as his facility can stay funded, he added, "there is a lot of fun to be had."