22 October 2008

Newly discovered electron crystal could help transform microelectronics

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TALLAHASSEE, Fla. — Using the strongest magnet in the world, McGill University researchers and their collaborators have discovered a new state of matter: a quasi-three-dimensional electron crystal. The discovery, in a material not unlike those used in the fabrication of modern transistors, could have momentous implications for the development of new electronic devices.

Currently, the number of transistors that can be crammed onto a single computer chip increases exponentially, doubling approximately every two years, a trend known as Moore's Law. But there are limits, experts say. As chips get smaller and smaller, scientists expect that the bizarre laws and behaviors of quantum physics will take over, making ever-smaller chips impossible.

This discovery, and similar efforts, could help the electronics industry when traditional manufacturing techniques approach these quantum limits over the next decade or so, the researchers said. Their results were published in the October issue of the journal Nature Physics.

Working with one of the purest semiconductor materials ever made, they discovered the quasi-three-dimensional electron crystal in a device cooled at ultra-low temperatures roughly 100 times colder than intergalactic space and placed in National High Magnetic Field Laboratory's 45 tesla hybrid magnet. (A tesla is a measurement of magnetic field strength; the Earth's magnetic field is one twenty thousandth of a tesla.)

Two-dimensional electron crystals were discovered in the laboratory in the 1990s, and were predicted as far back as 1934 by renowned Hungarian physicist Eugene Wigner. Until an accidental discovery during one of Gervais's earliest ultra-low temperature experiments in 2005, however, no one predicted the existence of quasi-three-dimensional electron crystals.

"We decided to tweak the two-dimensionality by applying a very large magnetic field, using the largest magnet in the world at the Magnet Lab in Florida," said Guillaume Gervais, director of McGill's Ultra-Low Temperature Condensed Matter Experiment Lab and a former postdoctoral associate at the Mag Lab. "You only have access to it for about five days a year, and on the third day, something totally unexpected popped."

Gervais's "pop" was the startling transformation of a two-dimensional electron system inside the semiconducting material into a quasi-three-dimensional system, something existing theory did not predict.

"It's actually not quite 3-D, it's an in-between state, a totally new phenomenon," he said. "This is the kind of thing the theoreticians love. Now they're scratching their heads and trying to fine-tune their models."

The importance of this discovery to micro-electronics and computing could be profound. Since the invention of the integrated circuit in 1958, Moore's Law has powered the ever-accelerating home electronics, personal computer and Internet revolutions that have changed the world. But, Gervais explained, Moore's Law is not an irresistible force, and some time in the next decade, it will inevitably collide with the laws of physics.

"In a standard transistor, you have a gate and the electron flow is controlled by it like a faucet would control a gas flow," he said. "You can understand the particles as independent units, which lets us treat them as ones and zeroes or on and off switches in digital computing.

"However, once you get down to the nano scale, quantum forces kick in and the electrons may condense into a collective state and lose their individual nature. Then all sorts of bizarre phenomena pop up. In some cases, the electrons may even split. Concepts of 'on' or 'off' lose all meaning under these conditions."

In addition to Gervais, co-authors on the paper include Benjamin Piot and Cory Dean, also of Montreal-based McGill; Lloyd Engel of the Magnet Lab and Zhigang Jiang of the Magnet Lab and Columbia University; and Loren Pfeiffer and Kenneth West of Bell Labs.

This news was adapted and published with the permission of its author, Mark Shainblum, and the McGill University media relations office.