Material created at Purdue lets electrons 'dance' and form new state

Jul 27, 2011 by Elizabeth K. Gardner
Material created at Purdue lets electrons 'dance' and form new state
Purdue professors Michael Manfra, from left, and Gabor Csathy stand next to the high-mobility gallium-arsenide molecular beam epitaxy system at the Birck Nanotechnology Center. Manfra holds a gallium-arsenide wafer on which his research team grows ultrapure gallium arsenide semiconductor crystals to observe new electron ground states that could have applications in high-speed quantum computing. Credit: Purdue University photo/Andrew Hancock

A team of Purdue University researchers is among a small group in the world that has successfully created ultrapure material that captures new states of matter and could have applications in high-speed quantum computing.

The material, , is used to observe states in which no longer obey the laws of single-particle physics, but instead are governed by their mutual interactions.

Michael Manfra, the William F. and Patty J. Miller Associate Professor of Physics who leads the group, said the work provides new insights into .

"These exotic states are beyond the standard models of solid-state physics and are at the frontier of what we understand and what we don't understand," said Manfra, who also is an associate professor of both materials engineering and electrical and computer engineering. "They don't exist in most standard materials, but only under special conditions in ultrapure gallium arsenide semiconductor crystals."

Quantum computing is based on using the quantum mechanical behavior of electrons to create a new way to store and process information that is faster, more powerful and more efficient than classical computing. It taps into the ability of these particles to be put into a correlated state in which a change applied to one particle is instantly reflected by the others. If these processes can be controlled, they could be used to create parallel processing to perform calculations that are impossible on classical computers.

"If we could harness this electron behavior in a semiconductor, it may be a viable approach to building a quantum computer," Manfra said. "Of course this work is just in its very early stages, and although it is very relevant to quantum computation, we are a long way off from that. Foremost at this point is the chance to glimpse unexplained physical phenomena and new particles."

Manfra and his research team designed and built equipment called a high-mobility gallium-arsenide molecular beam epitaxy system, or MBE, that is housed at Purdue's Birck Nanotechnology Center. The equipment makes ultrapure semiconductor materials with atomic-layer precision. The material is a perfectly aligned lattice of gallium and arsenic atoms that can capture electrons on a two-dimensional plane, eliminating their ability to move up and down and limiting their movement to front-to-back and side-to-side.

"We are basically capturing the electrons within microscopic wells and forcing them to interact only with each other," he said. "The material must be very pure to accomplish this. Any impurities that made their way in would cause the electrons to scatter and ruin the fragile correlated state."

The electrons also need to be cooled to extremely low temperatures and a magnetic field is applied to achieve the desired conditions to reach the correlated state.

Gabor Csathy, an assistant professor of physics, is able to cool the material and electrons to 5 millikelvin - close to absolute zero or 460 degrees below zero Fahrenheit - using special equipment in his lab.

"At room temperature, electrons are known to behave like billiard balls on a pool table, bouncing off of the sides and off of each other, and obey the laws of classical mechanics," Csathy said. "As the temperature is lowered, electrons calm down and become aware of the presence of neighboring electrons. A collective motion of the electrons is then possible, and this collective motion is described by the laws of quantum mechanics."

The electrons do a complex dance to try to find the best arrangement for them to achieve the minimum energy level and eventually form new patterns, or ground states, he said.

Csathy, who specializes in quantum transport in semiconductors, takes the difficult measurements of the electrons' movement. The standard metric of semiconductor quality is electron mobility measured in centimeters squared per volt-second. The group recently achieved an electron mobility measurement of 22 million centimeters squared per volt-second, which puts them among the top two to three groups in the world, he said.

Manfra and Csathy presented their work at Microsoft's prestigious Station Q summer meeting on June 17 at the University of California at Santa Barbara. This meeting, sponsored by Microsoft Research, brings together leading researchers to discuss novel approaches to . They also received a $700,000 grant from the Department of Energy based on their preliminary results.

In addition to Manfra and Csathy, the research team includes associate professors of physics Leonid Rokhinson and Yuli Lyanda-GElizabeth K. Gardnereller; professor of physics Gabriele Giuliani; graduate students John Watson, Nodar Samkharadze, Nianpei Deng and Sumit Mondal; and research engineer Geoff Gardner.

"A broad team is necessary to probe this type of physics," Manfra said. "It takes a high level of expertise in materials, measurement and theory that is not often found at one institution. It is the depth of talent at Purdue and ability to easily work with researchers in other areas that made these achievements possible."

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User comments : 9

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Telekinetic
1 / 5 (4) Jul 28, 2011
Incredible and fascinating. I predict that this work, at the present involving quantum entanglement, will lead to the detection of dimensions heretofore unknown.
Eoprime
not rated yet Jul 28, 2011
Incredible and fascinating. I predict that this work, at the present involving quantum entanglement, will lead to the detection of dimensions heretofore unknown.


Why?
Telekinetic
1 / 5 (4) Jul 28, 2011
Incredible and fascinating. I predict that this work, at the present involving quantum entanglement, will lead to the detection of dimensions heretofore unknown.


Why?

The question is "How?" would this lead to the detection of unknown dimensions. What they've invented could become a new sensor even though it's intended for quantum computing. The questions that will naturally follow entanglement are 'what are the media or paths by which entanglements are possible at great distances?' I'm speculating that it is through other dimensions that this phenomenon occurs. I'm not claiming to be the originator of the idea or know how to build this detector, but this array of electrons could be a component. As the researcher here says:
"Foremost at this point is the chance to glimpse unexplained physical phenomena and new particles."
Laminate
1 / 5 (1) Jul 29, 2011
Telekinetic,

When you say dimension, do you mean an alternate universe? or by dimension are you talking about some higher manifold that we might be embedded in?

Either way, conservation of energy prevents us from observing the effects of either directly, and this is no exception. Please quit filling forums with fringe science that casual readers mistake for actual progress.
Telekinetic
1.8 / 5 (5) Jul 29, 2011
"The Many-Worlds Interpretation (MWI) is an approach to quantum mechanics according to which, in addition to the world we are aware of directly, there are many other similar worlds which exist in parallel at the same space and time. The existence of the other worlds makes it possible to remove randomness and action at a distance from quantum theory and thus from all physics."
And I will ask you to expand your very circumscribed knowledge of theory before posting criticism that only embarrasses yourself.
Laminate
not rated yet Jul 29, 2011
@ Telekinetic

Everett's MWI was more of a thought experiment than anything. Unfortunately for you, if MWI is the underlying nature for the behavior of quantum mechanics, there's an infinite number of possible universes, none of which can be observed after an observation has caused a wavefunction of an event to collapse into any given world of the MWI so the point is moot and trivial.

Also, the Orthodox (copenhagen interpretation) is the most widely accepted view for the explanation of the effects that observation has on a system. When you get down to it, no matter what theory predicts multiple realities (m-theory) higher dimensional manifolds, or MWI, these "dimensions" as you put it are completely cut off from our observable universe and are impossible to reach.
Telekinetic
1 / 5 (4) Jul 30, 2011
"When you get down to it, no matter what theory predicts multiple realities (m-theory) higher dimensional manifolds, or MWI, these "dimensions" as you put it are completely cut off from our observable universe and are impossible to reach."

Well, now that I've opened your mind up to accepted theories that you no longer refer to as "fringe science", your use of the phrase "impossible to reach" puts you back in the category of those who are ultimately incapable of understanding what the principles of discovery are, and you'll be left in the dust when these dimensions are eventually confirmed.
Laminate
not rated yet Jul 30, 2011
These theories are hardly accepted as none of them are complete nor do they offer adequate mechanisms as explanation for the phenomena that supposedly causes it. I'm not a naysayer when it comes things concerning the limit of our understanding, but the point is, is that a many worlds style reality implies there's infinite energy available. It also implies that there can be an exchange of information, and energy between these universes. Of course this "could" be possible but is highly speculative, to say the least and to suggest that a new method of electron measurement could be used to detect multiple realities that are not even defined is little more than science fiction fantasy.
Telekinetic
1 / 5 (4) Jul 30, 2011
"Of course this "could" be possible but is highly speculative, to say the least and to suggest that a new method of electron measurement could be used to detect multiple realities that are not even defined is little more than science fiction fantasy."

Once again, you lack the capacity to see what's in front of your nose, which is cutting edge science that IS widely accepted. Instead of gleaning your information from Wikipedia, try getting a hold of the May 2nd issue of The New Yorker, that discusses the work of David Deutsch, whose work in MWI is being closely followed by many physicists. I'm beginning to think you're a glutton for punishment.