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Main Question or Discussion Point
if helium is 'superfluid' at low temperatures then is it correct to think of amorphous solids as 'superviscous'?
What would be the properties of a superviscous amorphos soild?if helium is 'superfluid' at low temperatures then is it correct to think of amorphous solids as 'superviscous'?
Superfluidity is a quantum effect, where the glass transition is a classical effect, as far as I know.if helium is 'superfluid' at low temperatures then is it correct to think of amorphous solids as 'superviscous'?
I am not sure why you think superinsulators have anything to do with this; they are essentially just grainy films where the charging energy of single grains are larger than the availalble thermal energy which means that the charge carriers "freeze out" at low temperatures (it is a bit more complictated than this, since there are some collective effects involved, but that is the essence of it); it is essentially a classical effect and there is no macroscopic coherence involved.
Well, the Wikipedia article isn't very accurate in this case. It is true that the effect is observed when the grains are superconducting; but this does not change what I wrote above. If you want you can think of the system as a network of Cooper pair boxes (which is why you need the grains to be superconducting); but the interaction between these are -as far as I know- still just classical (there is a synchronization of the phase BETWEEN the grains; but there is still no GLOBAL phase; the system is not described by a "single wavefunction").according to the wikipedia article superinsulators are the result of cooper pairs and the effect can be destroyed by magnetic fields.
also see:
http://www.nature.com/nature/journal/v452/n7187/abs/nature06837.html
Although the theory that frozen helium might be a supersolid has been around for years, the first evidence that it was at least a super-something was provided in a 2004 experiment by Moses Chan at Penn State. Researchers there placed a tiny cylinder of frozen helium in a torsion oscillator, which rotates rapidly forward and back, like a washing machine agitator. The resonant frequency of the oscillator -- the one it naturally settles into -- depends on the mass it's trying to move around and back. The researchers found that below a critical temperature, some of the mass of the (solid) helium seemed to disappear.
Physicists in the US have shown that a supposed quantum phase of matter known as a "supersolid" is strongly dependent on the amount of crystal disorder present in the sample being studied. By performing experiments on samples of helium-4 with large amounts of disorder, they found that the trademark effects of supersolidity in the samples rose to more than 20% -- by far the largest proportion seen so far.
Helium II is a superfluid, a quantum-mechanical state of matter with strange properties. For example, when it flows through even capillaries of 10-7 to 10-8 m width it has no measurable viscosity. However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium was observed (which is still pretty small for a fluid). Current theory explains this using the two-fluid model for Helium II. In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a ground state, which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid.
granpa said:I think that most people would agree that the electron doesnt really spin. it just behaves as though it did. I'm thinking that the supercurrent is like that. the cooper pairs dont (necessarily) move. they just behave as though they did.
http://en.wikipedia.org/wiki/London_momentA more fundamental property than the disappearance of viscosity becomes visible if superfluid is placed in a rotating container. Instead of rotating uniformly with the container, the rotating state consists of quantized vortices. That is, when the container is rotated at speed below the first critical velocity (related to the quantum numbers for the element in question)(its the speed of sound in the superfluid) the liquid remains perfectly stationary.
in other words the electrons (or rather cooper pairs) are stationary.The London moment is a quantum-mechanical phenomenon whereby a spinning superconductor generates a magnetic field whose axis lines up exactly with the spin axis. The term may also refer to the magnetic moment of any rotation of any superconductor, caused by the electrons lagging behind the rotation of the object.
Although the theory that frozen helium might be a supersolid has been around for years, the first evidence that it was at least a super-something was provided in a 2004 experiment by Moses Chan at Penn State. Researchers there placed a tiny cylinder of frozen helium in a torsion oscillator, which rotates rapidly forward and back, like a washing machine agitator. The resonant frequency of the oscillator -- the one it naturally settles into -- depends on the mass it's trying to move around and back. The researchers found that below a critical temperature, some of the mass of the (solid) helium seemed to disappear.
Application of heat to a spot in superfluid helium results in a wave of heat conduction at the relatively high velocity of 20 m/s, called second sound.
the article says that superfluid helium behaves as though it has 2 ocmponents. the real atoms would be the second component. the component that flows with little but not zero viscosity.(of course, real atoms can and do really flow but it wouldnt be with zero viscosity. the viscosity might be pretty small though)