What Is Superfluidity ?

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What Are Superfluids ?
Superfluids are, like superconductors, related to the behaviour of materials at very low temperatures. Superfluids can only observed at much lower temperatures than superconductors, Helium-4 doesn't display superfluid-behaviour until nearly below 2K. and these temperatures are not easy to reach.

When a material does become a superfluid, it displays some very strange behaviour; The Lambda Point
There are other interesting facts about superfluids, the point at which a liquid becomes a superfluid is named the lambda point. This is because at around this area the graph of specific heat capacity against temperature is shaped like the greek letter l.

The relationship at the superfluidity boundary of Helium-4,
between its specific heat capacity and its temperature.

The graph has an asymptote at its lambda point; this is when the atoms are moving slowly enough to form a single energy state, and are then unaffected by other atoms. Above the lambda point the atoms all move about in a disordered way, but below this temperature they all move in an organised way. We can see these effects in Helium-4 becuse it is still a liquid at these low temperatures; most materials solidify above these temperatures.

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Page Contributed by John Duffell, Year 13 student 1999-2000