Experimental evidence adds to the likelihood of the existence of supersolids, an exotic phase of matter

Feb 18, 2011
Figure 1: A custom-developed rotating cryostat capable of 15 millikelvin temperatures is helping physicists find evidence for the existence of supersolids. Credit: 2011 Kimitoshi Kono and Eunseong Kim

Supersolids and superfluids rank among the most exotic of quantum mechanical phenomena. Superfluids can flow without any viscosity, and experience no friction as they flow along the walls of a container, because their atoms 'condense' into a highly coherent state of matter. Supersolids are also characterized by coherent effects, but between vacancies in a crystal lattice rather than between the solid’s atoms themselves.

The reduction in the rotational inertia of a bar of solid helium-4 as it was cooled to very low temperatures provided the first experimental evidence for supersolids. Physicists interpreted the reduction to mean that some amount of supersolid helium had formed and decoupled from the remainder of the bar, affecting its rotational inertia and frequency. Others argued that the reduction in inertia resulted from a change in the helium’s viscosity and elasticity with temperature, rather than from the onset of supersolidity.

Kimitoshi Kono from the RIKEN Advanced Science Institute in Wako, Japan, Eunseong Kim from KAIST in Korea, and their colleagues from these institutes have now disproved the alternative interpretation by simultaneously measuring the shear modulus (a measure of and elasticity) and the rotational inertia of a solid helium-4 cell as its temperature dropped from 1 kelvin to 15 thousandths of a kelvin. The cell was made to rotate clockwise and then counterclockwise periodically, as well as to rotate clockwise or counterclockwise continuously (Fig. 1). The continuous rotation affected the inertial mass of the helium but its shear modulus, allowing these quantities to be monitored independently.

Under continuous rotation, the degree of change in the rotational inertia had a clear dependence on rotation velocity, while the shear modulus did not. In addition, the energy dissipated by the rotation increased at high speeds. Both of these observations contrast to what would be expected if viscoelastic effects were at play, rather than supersolidity. The researchers also found that periodic rotation and continuous rotation affected the rotation differently, raising new questions about the experimental system.

The data support the interpretation that changes in the rotational inertia of helium-4 at low temperature result from supersolidity. This is important because of the novel and surprising nature of the phenomenon itself, says Kono. “Superfluidity in a solid is a very radical concept which, if proven, is certainly a good candidate for the Nobel Prize” he adds. “Therefore the first priority is to determine whether it can be proven in a fashion that will convince the low-temperature physics community.”

Explore further: Liquid spacetime: A very slippery superfluid, that's what spacetime could be like

More information: Choi, H., et al. Evidence of supersolidity in rotating solid helium. Science 330, 1512–1515 (2010). www.sciencemag.org/content/330/6010/1512.abstract

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Moebius
4 / 5 (4) Feb 18, 2011
"The continuous rotation affected the inertial mass of the helium but its shear modulus, allowing these quantities to be monitored independently."

I am assuming that the word NOT was omitted from this sentence in the article and should have read:

"The continuous rotation affected the inertial mass of the helium but NOT its shear modulus, allowing these quantities to be monitored independently."

Does no one proofread what they write anymore?
TheQuietMan
not rated yet Feb 18, 2011
I understand super fluids (OK, maybe I don't, I have the concept down), but what is a super solid again?
QuantaUniverseCom
1.7 / 5 (6) Feb 18, 2011
the planck scale could be a super state of matter and seen as grainy blurry
HolographicGalaxy.blogspot.com
that_guy
4.2 / 5 (5) Feb 18, 2011
"The continuous rotation affected the inertial mass of the helium but its shear modulus, allowing these quantities to be monitored independently."

I am assuming that the word NOT was omitted from this sentence in the article and should have read:

"The continuous rotation affected the inertial mass of the helium but NOT its shear modulus, allowing these quantities to be monitored independently."

Does no one proofread what they write anymore?


I've noticed, msn, pcmag, cnn,...its like the entire internet doesn't have a single copy editor.
Macksb
3 / 5 (4) Feb 18, 2011
Let's suppose that the 2004 Penn State experiment is valid, and properly interpreted as a supersolid.

If so, there is a possible theoretical explanation that has not yet been suggested, to my knowledge. Think of a supersolid as two states of matter--superfluid and solid--coexisting. One could be viewed as the normal state and the other could be viewed as a "chimera" state. (Look it up.)

There is a 2008 PRL article by Abrams, Mirollo, Strogatz and Wiley entitled "Solvable Model for Chimera States of Coupled Oscillators."

I have also suggested this article as a possible theoretical explanation for the recent Livermore Lab experiment involving cerium, which produced two different cerium crystals--one larger, one smaller--produced under extremely high pressure. See the Phys Org article entitled "Cerium's Unusual Behavior," Jan 27 2011.

Both of these intriguing results may share the same explanation.
beelize54
2.1 / 5 (7) Feb 18, 2011
I understand super fluids (OK, maybe I don't, I have the concept down), but what is a super solid again
Basically it's the point, many solids keep the thin layer of the molten phase at their surfaces, for example the surface of ice is covered with thin layer of water, which makes ice so slippery. Analogously, I presume, the crystalline domains of solid helium-3 are covered with superfluid hellium. The asymmetry of He-3 atoms helps in it in similar way, like the asymmetry of water molecules, because the He-4 (the atom nuclei of which is composed of two protons and two neutrons) doesn't exhibit supersolidity.

IMO the well known crackling and crunching of snow has its origin in the same phenomena - in another words, snow appears supersolid at least for brief period of time, when exposed to external pressure. Another example of this mechanism is the ballistic transport of electrons at the surface of graphene.
Macksb
1 / 5 (1) Feb 19, 2011
Following up on my prior post, the 2008 PRL article to which I referred begins as follows: "Networks of identical, symmetrically coupled oscillators can spontaneously split into synchronized and desynchronized subpopulations."

The helium and cerium experiments to which I refer in my prior post both meet that general condition. They are networks of identical oscillators. And they are symmetrically coupled, pre-split.

Later in that same article, the authors explain the mathematically possible outcomes of such spontaneous splits. A stable chimera is one possibility. I say the cerium experiment at Lawrence Livermore is an example. A "breathing chimera" state is another possibility. I say the supersolid helium case (Penn State experiment) is an example. "The order parameter pulsates, and the chimera starts to breathe" as the authors say, colorfully, in their 2008 article. That's Kim and Chan's (the Penn State guys) torsional oscillator, which produces superfluid as the chimera.
Macksb
1 / 5 (1) Feb 19, 2011
The balance wheel rotations in the Penn State experiment, back and forth, are a key element. That oscillation stresses the solid helium, causing the solid to slough off a (less fully coupled) fluid (a superfluid, in this case). The external oscillations are similar in this way to external magnetic oscillations hitting a superconductor, causing it to break down once the external force reaches a certain level. In the Penn State experiment, the broken down result is, confusingly, a superfluid, which attracts our attention. But in fact, the superfluid is disordered as compared with the solid helium. That's why I say the superfluid is the chimera portion.

These two apparently special cases--the cerium chimera and the helium chimera--are not special. They simply prove that Art Winfree's coupled oscillator theory is the equivalent of plate tectonics, explaining all phases of matter and their transitions.
hush1
1 / 5 (2) Feb 20, 2011
Does reducing volume (decreasing temperature, increasing density)increase (rotational) inertia?
In a "lossless" (no energy dissipated) medium?

In addition, the energy dissipated by the rotation increased at high speeds.


Does shear modulus exist? In an incompressible sphere? Liquid or solid?

Please ignore (habitual out loud thinking)

Nobel - the motivation?

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