Superfluid



  Superfluidity is a phase of matter or description of heat capacity in which "unusual" effects are observed when quantum hydrodynamics, it was discovered by Pyotr Kapitsa, John F. Allen, and Don Misener in 1937 and has been described through phenomenological and microscopic theories.

Background

Although the phenomenologies of the superfluid states of helium-4 and fermion condensate. A unified description of superconductivity and superfluidity is possible in terms of gauge symmetry breaking.

Superfluids, such as supercooled helium-4, exhibit many unusual properties. A superfluid acts as if it were a mixture of a normal component, with all the properties associated with normal fluid, and a superfluid component. The superfluid component has zero Clausius-Clapeyron relation. A second unusual effect is that superfluid helium can form a layer, a single atom thick, up the sides of any container in which it is placed.

A 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 element in question) the liquid remains perfectly stationary. Once the first critical velocity is reached, the superfluid will very quickly begin spinning at the critical speed. The speed is quantized - i.e. it can only spin at certain speeds.

Applications

Recently in the field of molecule solvated in a superfluid medium allows a molecule to have effective rotational freedom - allowing it to behave exactly as it would in the "gas" phase.

Superfluids are also used in high-precision devices, such as gyroscopes, which allow the measurement of some theoretically predicted gravitational effects (for an example see the Gravity Probe B article).

Recently, superfluids have been used to trap and slow the speed of light. In an experiment, performed by Lene Hau, light was passed through a superfluid and found to be slowed to 17 meters per second (normally 299,792,458 meters per second).[1]

The Infrared Astronomical Satellite (IRAS), launched in January 1983 to gather infrared data was cooled by 720 litres of superfluid helium, maintaining a temperature of 1.6K (-271.6 ­°C).

Recent discoveries

Physicists have recently been able to create a Fermionic condensate from pairs of ultra-cold fermionic atoms. Under certain conditions, fermion pairs form Bose–Einstein condensation. At the other limit, the fermions (most notably superconducting electrons) form Cooper pairs which also exhibit superfluidity. This recent work with ultra-cold atomic gases has allowed scientists to study the region in between these two extremes, known as the BEC-BCS crossover.

Additionally, solid appears to become superfluid [1].

Notes and References

  1. ^ Lene Vestergaard Hau, S. E. Harris, Zachary Dutton, Cyrus H. Behroozi Light speed reduction to 17 metres per second in an ultracold atomic gas Nature 397, 594-598 (18 February 1999)
  • Hagen Kleinert, Gauge Fields in Condensed Matter, Vol. I, "SUPERFLOW AND VORTEX LINES", pp. 1–742, World Scientific (Singapore, 1989); Paperback ISBN 9971-5-0210-0 (also available online here)

See also
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Superfluid". A list of authors is available in Wikipedia.