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Scientists Create Supersolid From Helium
jabberjaw writes "Nature is reporting that Pennsylvania State University researchers Eun-Seong Kim and Moses Chan have created a 'supersolid' from helium-4. Although a crystalline solid, the supersolid can flow much like a liquid. This is due to the fact that the empty compartments in the crystal move coherently, thus waves can progress through the lattice. The supersolid state can be compared to the superfluid state. Perhaps a condensed matter physicist can dumb the article down for layfolk such as myself?"
Joyous helium
Becomes a supersolid
At low Celcius
But seriously, this stuff is really cool. What with the properties they described, I wonder if it could be useful in conducting electricity or forming a shock-absorbing barrier?
Cyde Weys Musings - Scrutinizing the inscrutable
My dad did his PhD thesis on liquid helium 3. Apparently it's pretty difficult to contain the stuff, since even the tiniest opening in a container is enough for everything to escape at once (no viscosity)...
A superfluid is a fluid that flows without viscosity, meaning that if you were to stir a spoon in a superfluid soup, you could take out the spoon and the soup would keep swirling forever on, since there is no mechanism there (i. e. no friction) to make the vortex you just made disappear. Now if you were to cool a 4He crystal, there would be eventually be no more movement of atoms and the whole thing froze out. But in quantum mechanics, there is the Heisenberg uncertainty Principle which basically states that you are not to now the position of any particle along with its velocity with the same accuracy. There will always be a trade off. The better you know the position, the worse you know the velocity. This accounts for the fact that even at absolute zero, there are some fluctuations of particles, called quantum fluctuations wich do never freeze out. When a superfluid appears this means that the atoms in it move all together. As the Nature article suggests, you can compare this to soldiers on a parade. They all move alike. In a supersolid then, you have vacancies, places where atoms are absent. Think of holes in a semiconductor if you like. There, holes are just non-electrons. Here we deal with non-atoms, and they are the ones behaving like soldiers in the case of a supersolid. Meaning the propagate through the whole thing as if they were on a parade, which makes them great for sending any wave (electromagnetic or other) through the crystal, and since these vacancies move in order, they propagate the wave without damping it. This would make a hell of an amplifier. Compare the situation to a superconductor, where you can propagate electric current without damping (i. e. having no resistance at all). To electric current, a superconductor behaves like a supersolid to waves of any kind.
Black holes were created when god tried to divide by zero
In actuality, superfluids do NOT have zero viscosity at all points. They have very complex properties, depending on a combination of the container, exact conditions, etc, etc. Typically, some parts of superfluids exhibit zero viscosity (truly zero), leading to some fascinating fluid mechanics. For example, the Stokes singular problem actually has NO boundary layer, so drag goes to zero. There are plenty of other really interesting phenomenon - some that might be utilized in future technology.
Other interesting properties of superfluids include rather odd magnetic fields (Helium-3 or 4 is odd to start with, and then chilling it down and spinning it does some interesting stuff), VERY odd conduction, etc, etc. I imagine that there will be future Nobel prizes given out for research in this area (I believe one already has been, a few years back). Studying how superfluids act can give us some very interesting insights into what actually happens in various media at tiny sizes. One example would be looking at fluid/solid interfaces, and trying to determine what precisely goes on there. The possibilities are endless...
That being said, isn't the official definition of a fluid "something that deforms continuously under shear stress"? As such, does this indicate that these supersolids do NOT flow continuously?
"Don't bother me with that pocket calculator stuff" - Deep Thought
"Perhaps a condensed matter physicist can dumb the article down for layfolk such as myself?"
Imagine a big block of swiss cheese (the kind of cheese that's got all the holes in it). Now those holes are basically "vacancies" of cheese. Now, imagine if the holes moved around.
Similarly, think of one of those pictures underwater videos of SCUBA divers... You know when they release a breath, and all the bubbles start moving up to the surface of the water... Those are likes 'holes' in the water. More specifically, they are "vacancies" and they move in a somewhat orderly manner (up). Of course, it makes more common sense that vacancies would move around in a liquid than in solids....
So, basically, they've found a state of matter where the vacancies move around in a solid. In a sense, they're claiming that they found a block of cheese in the refridgerator where the holes keep moving. And this is why there's going to be controversy over this claim: they're alot of people who are going to say "no way - cheese doesn't work that way..."
It would make for a crazy club sandwich... Yum.
FYI: I'm not a condenced matter physicist, although I do happen to have a degree in the History and Philosophy of Science...