Thursday, June 18, 2009

Room Temperature Superconductors One Step Closer

We are one step closer to room temperature superconductors.
Menlo Park, Calif.—Move over, silicon—it may be time to give the Valley a new name. Physicists at the Department of Energy's (DOE) SLAC National Accelerator Laboratory and Stanford University have confirmed the existence of a type of material that could one day provide dramatically faster, more efficient computer chips.

Recently-predicted and much-sought, the material allows electrons on its surface to travel with no loss of energy at room temperatures and can be fabricated using existing semiconductor technologies. Such material could provide a leap in microchip speeds, and even become the bedrock of an entirely new kind of computing industry based on spintronics, the next evolution of electronics.

Physicists Yulin Chen, Zhi-Xun Shen and their colleagues tested the behavior of electrons in the compound bismuth telluride. The results, published online June 11 in Science Express, show a clear signature of what is called a topological insulator, a material that enables the free flow of electrons across its surface with no loss of energy.
Pretty darn exciting. It all depends on something called topological insulation. The article gives some details on how that works. Which gets a bit heavy on the physics. I'm going to skip that here. However, if you have heard of the Pauli exclusion principle it is worth a read.

There are some limitations. For now.
Topological insulators aren't conventional superconductors nor fodder for super-efficient power lines, as they can only carry small currents, but they could pave the way for a paradigm shift in microchip development. "This could lead to new applications of spintronics, or using the electron spin to carry information," Qi said. "Whether or not it can build better wires, I'm optimistic it can lead to new devices, transistors, and spintronics devices."

Fortunately for real-world applications, bismuth telluride is fairly simple to grow and work with. Chen said, "It's a three-dimensional material, so it's easy to fabricate with the current mature semiconductor technology. It's also easy to dope—you can tune the properties relatively easily."

"This is already a very exciting thing," he said, adding that the material "could let us make a device with new operating principles."
Bismuth Telluride is a semiconductor that is currently used for solid state refrigerators. It is also used to generate electricity from small temperature differences. That means the semiconductor industry has more than a little experience in fabricating the material.

If the lab boys have developed a repeatable formula it is possible we might see useful devices using this superconducting property in as little as three years. One use of such properties might be to make a super low noise microwave filter that doesn't require cooling to Liquid Nitrogen temperatures (77° Kelvin). That could be very helpful.

I will be keeping an eye on this one.

If "normal" superconductivity interests you this book is a good place to start:
Introduction to Superconductivity

And if you are a little further along and contemplate building a fusion reactor in your garage, this book could help:
Case Studies in Superconducting Magnets: Design and Operational Issues

More books:

Superconductivity

Handbook of Superconductivity

Engineering Superconductivity

6 comments:

Doug Natelson said...

I hate to break it to you, but this material has nothing whatsoever to do with superconductivity.

M. Simon said...

No loss of energy sounds like a superconductor to me. Jc may be severely limited but there are still a lot of uses in electronics for a low Jc room temperature superconductor.

Doug Natelson said...

Trust me - I'm a condensed matter physicist, and dissipationless spin currents in topological insulators have nothing to do with superconductivity, except in one very formal mathematical sense.

Loosely speaking, in a superconductor, electrons pair up and those pairs "condense" into a particular kind of "fluid". That fluid can carry charge and flow without dissipation. That's because it costs a finite amount of energy to break up a pair. (In an ordinary metal one can dump an arbitrarily small amount of energy into the electrons. In a superconductor, if a process doesn't have enough energy to break a pair, it can't dump energy into the electrons.)

In these topological insulators (note that they're bulk insulators), one can have spin currents, where more spin-up electrons flow one direction and spin-down electrons flow the opposite way. This kind of current transports spin (the magnetic moment of electrons) without dissipation, but it does not transport charge. Because they don't transport charge, you cannot use spin currents to, for example, run an electric motor. Now, you may be able to use spin currents in computing, since there are clever ideas about how to store information using spin. However, this has no application for power transmission or distribution. There are some other neat features of topological insulators, but these have nothing to do with superconductivity.

The formal similarity between topological insulators and superconductors is that they both have an energy gap - it costs a certain minimum amount of energy to make a low energy excitation of the system. However, those excitations are very different things.

You're right, of course, that a room temperature superconductor would be great, even if Jc and Bc are low. People are looking for such materials, but not these folks.

M. Simon said...

Doug,

Thanks for that. If the guys writing the article had just emphasized that spin was conserved it would have been a lot clearer.

Momma Bear said...

Amazing how far we've come in such a short time!! Keep doing what you're doing.. you guys.. ARE the REAL heroes of our world! Don't forget that fact!!

cash said...

The information about topological insulators and superconductors was interesting. Developing a room temperature superconductor would be useful since it could have a lot of applications.