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McGill physicists find a new state of matter in a "transistor"
Oct. 21, 2008
Could previously unknown type of electron crystal help the future of
electronics?
McGill University researchers have discovered a new state of matter, a
quasi-three-dimensional electron crystal, in a material very much alike
those used in the fabrication of modern transistors. This discovery
could have momentous implications for the development of new electronic
devices. Currently, the number of transistors that can be inexpensively
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 behaviours of quantum physics will take
over, making ever-smaller chips impossible.
This discovery, and other similar efforts, could help the electronics
industry once traditional manufacturing techniques approach these
quantum limits over the next decade or so, the researchers said. 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. The material was then exposed to the most powerful
continuous magnetic fields generated on Earth. Their results were
published in the October issue of the journal Nature Physics.
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.
“Picture a sandwich, and the ham in the middle is your electrons,”
explained Dr. Guillaume Gervais, director of McGill’s Ultra-Low
Temperature Condensed Matter Experiment Lab. “In a 2D electron crystal,
the electrons are squeezed between two materials and they’re very two
dimensional. They can move on a plane, like billiard balls on a pool
table, but there’s no up and down motion. There’s a thickness, but
they’re stuck.”
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,” he said. “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 which 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
immovable object of the laws of physics.
“In a standard transistor, you have a gate and the electron flow is
controlled by it like a 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’ and ‘off’ lose all
meaning under these conditions.”
“This issue is academic, but it’s not just academic. The same
semiconductor materials we’re working with are currently used in
cellphones and other electronic devices. We need to understand quantum
effects so we can use them to our own advantage and perhaps reinvent the
transistor altogether. That way, progress in electronics will keep
happening .”
Contact:
* Mark Shainblum, Media Relations Office - Tel.: 514 398-2189
See also:
* News releases
* Research
* Faculty of Science
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McGill University
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