Micro-tech center rethinks computing

Researchers at the C-SPIN want to harness electron spin for computing.

by Parker Lemke

A University of Minnesota-led research effort is putting a new spin on how computers work.

Facing growing limitations of current computing methods, the $28 million Center for Spintronic Materials, Interfaces and Novel Architectures has narrowed in on harnessing electron spin to create faster, energy-efficient computers.

Less than two years into the center’s five-year grant, its 32 experts hailing from 18 universities still have obstacles to overcome, including how to integrate cutting-edge research into usable devices.

But according to C-SPIN director and electrical and computer engineering professor Jian-Ping Wang, the center has already made several important discoveries since its opening in 2013.

A decades-old scientific law says the processing power of microchips doubles roughly every 18 months. But as the traditional transistors that power electronics grow smaller and smaller, it’s becoming more difficult to match technology with computer power, Wang said.

In as soon as five to 10 years, he said, technology will reach a point where it can no longer shrink at the same exponential rate at which computer performance is growing.

“Virtually any technology has this sort of scaling problem,” physics professor Paul Crowell said. “What do you do when you start approaching that atomic scale?”

In the past, manufacturers have increasingly added miniscule transistors, said Crowell, who is also one of C-SPIN’s co-directors.

“As a physicist, I can say that’s not really creative,” he said. “Maybe there’s a better way to do this.”

As one of six research centers funded by the Semiconductor Research Corporation’s STARnet program, C-SPIN boasts sponsorship from industry and government partners like Intel, IBM and the U.S. Department of Defense.

“It’s critical for the semiconductor industry to fund long-range research,” STARnet executive director Gilroy Vandentop said. “For the furthest-reaching research, the most risky research, we basically use universities as our research arm.”

Charge vs. spin

Conventional transistors work as on and off switches for gates that control electron current, Wang said.

Computer commands are based on whether charged electrons are flowing through various transistors.

But powering computing processes with electrons’ charge tends to waste a lot of energy, Wang said.

Electrons don’t just carry charges, though — every electron also has an up or down spin.

“Our circuits rely on the fact that electrons have charge, but they’re [also] carrying around this extra piece of information,” said Crowell, who works on transmitting spin information between different materials. “For the most part, we waste that.”

Controlling this extra component of electrons — which tend to spin in the same direction in magnetic materials — can open up new ways to compute data, said Caroline Ross, a C-SPIN researcher and materials science and engineering professor at the Massachusetts Institute of Technology.

“The way you would be encoding data could be not so much whether there’s a charge or not,” Ross said, “but whether you got a spin up or a spin down.”

Hard drives already use electron spin to magnetically store information, Wang said.

Today’s technology then transfers that magnetically stored information onto traditional charge-based computer processing and memory.

Now C-SPIN is trying to use electron spin as a low-energy alternative to electron charge.

“In order to accomplish this, you need advances in a lot of different areas,” Ross said.

Turning theory into
devices

The University’s laboratories are one in C-SPIN’s nationwide network of researchers and collaboration across 18 institutions.

The center, which the University leads, divides its workload into five themes that focus on areas like developing materials, transferring spin and building prototypes, Crowell said.

He said the development of materials like metal and semiconductors — as well as research on how they can be combined — has formed the basic components of spin-based processing.

“The next step after that is to turn it into something useful,” Crowell said.

That’s where electrical engineering doctoral student Angeline Klemm comes in. She spends her weeks in
C-SPIN’s labs fabricating, testing and tweaking tiny devices.

“[I] kind of repeat, adjust what I need for the new samples [and] do the fabrication again,” she said.

While the center has made progress in each of its themes, Crowell said, the ones focused on building devices rely on a pipeline of advancements from the other, more foundational research.

But impediments like the fragile nature of some new materials can make them difficult to work with at times. Crowell said they can be particularly sensitive to temperature.

“Things work fantastic at low temperatures — below room temperature — but of course that’s not where computers are used,”
Crowell said.