Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Solid helium

  1. Jun 6, 2006 #1
    :cool: :smile: :cool: Can anybody tell me what is the meaning of a quantum crystall? I've heard it is referred to a lattice with vibrations over harmonic approximation. If so, what about the consequences?
  2. jcsd
  3. Jun 16, 2006 #2
    The meaning?
    Generally, a 'quantum crystal' can be thought of as the very unusual state of a BEC in solid form, i.e., solid helium, for ex., characterized by quantum phase coherence macroscopically. I've heard it can be described otherwise.

    The consequences are very counter intuitive .... a quantum solid is predicted to exhibit superfluidity, and apparently that is what happens. Some call it super solid; I refer to it as supersolidity. If it were possible to put a pure sample on a rotating turntable, the sample would not move :biggrin:
    Is that what you had in mind?

    Last edited: Jun 16, 2006
  4. Jun 16, 2006 #3

    Is that because it has no friction? Also is solid gas possible, sorry but I'm not too skilled in this area?
  5. Jun 18, 2006 #4
    It is a purely quantum effect, and, yes, one result is that the quantum fluid (or in this case the quantum solid, say He-4) experiences no 'friction' with the 'container'. However, the implications are more far reaching.

    Recent solid He-4 experiments apparently reveal that this quantum effect allows solid He-4 to "pass through" another solid while both are in solid phase. :surprised
    Isn't QM interesting. :wink:

    Creator :biggrin:
  6. Jun 18, 2006 #5
    Could we use the He-4 as an Atmospheric Envelope leaking through the pores of a Space Craft/Air Craft Skin to allow the vehicles to experience Zero Friction, If the He-4 oozes from the Skin pores wouldn't it allow for this? Frictionless Flight.
  7. Jun 19, 2006 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No it wouldn't.

    I would strongly recommend anyone that wishes to talk about supersolidity, please, first read the paper by Kim and Chan...please.

  8. Jun 19, 2006 #7
    Nice idea, Intuitive; but as is commonly the case with cryogenic quantum effects, the practical applications remain distant.
    In this case...
    Solid He-4 melting point is around 0.2 *Kelvin, and requires high pressure to remain solid.

    Nevertheless, at such low temp. and high pressure the solid 'superflow' effect remains real. However, it is not 100% as in the case of liquid helium superfluidity; rather only a small percentage of the solid becomes superflow below the melting point, (and if I'm not mistaken the % has a temp./pressure dependency).

    Last edited: Jun 19, 2006
  9. Jun 19, 2006 #8
    Very informative, Thanks.

    Would you happen to know what the Atmospheric Pressure of Air is that is entering into an Air intake Ram at Mach 10?

    From the link that Gokul43201 gave me to read inwhich I spent a couple of hours visiting links from that link as well and some others, it still looks like there is some engineering hope by using the vehicles own energy and areodynamics to give us what we need for the He-4 transition to take place couldn't it if we're dealing with high Mach numbers to play with?

    Just trying to work out some Engineering details for more troubleshooting questions.

    Something like this that uses micro Skin Riffles with Capularies exposed to high Mach Pressures.

    Attached Files:

    • H4.gif
      File size:
      5.2 KB
    Last edited: Jun 19, 2006
  10. Jun 19, 2006 #9
    I still don't think so :uhh: for the same reasons I gave before. For example, how are you going to keep the temperature below 0.2*K while it is exposed to the atmosphere? I've seen engineers who appear to work miracles, but they still have to stay within the confines of physical law.:biggrin:

    If you're looking for reduction in friction or drag through a medium you may want to try something akin to super-cavitation that has recently been used to increase torpedo underwater velocities to several hundred mph.
    Microscopic bubbles are released along the laminar flow of the surface of the structure as it moves through the medium.

    BTW; front surface pressure scales as the square of the velocity; (so, for ex., the force on a surface from a head on 200 mph wind is 4 times that of a 100 mph velocity.)

    However, I don't want to high jack the OP's original intent.

    More details of Moses Chan's He-4 work via torsional oscillations is found in Science, vol 305, p.1941, 2004.

    Last edited: Jun 19, 2006
  11. Jun 19, 2006 #10
    So does this BOSE-Einstein condensation thing, mean that wood and all materials can be turned into lets say, liquid?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Solid helium
  1. Helium Purging (Replies: 4)