helium-4

This is the first demonstration of whistling in superfluid helium-4.

Boing Boing: January 23, 2005 - January 29, 2005 Archives 2005

This was long after Kapitsa's discovery of superfluidity in a liquid of naturally occurring helium, which is completely dominated by the heavier isotope helium-4.

The Nobel Prize in Physics 2003 - Presentation Speech 2003

This chemical element exists in two forms, or isotopes: a heavier one called helium-4 and a lighter one called helium-3.

The Nobel Prize in Physics 1996 - Presentation Speech 1997

Superfluidity is a remarkable and unusual property that had previously been observed only in helium-4.

The Nobel Prize in Physics 1996 - Presentation Speech 1997

For this reason superfluidity should not be possible in helium-3 which, like helium-4, can be liquidised at a temperature of some degrees above absolute zero.

Press Release: The 1996 Nobel Prize in Physics 1996

This superfluid quantum liquid differs greatly from the one already discovered in the 1930s and studied at about two degrees (i.e. a thousand times) higher temperature in the normal helium isotope helium-4.

Press Release: The 1996 Nobel Prize in Physics 1996

Helium mainly consists of the isotope helium-4, which is a boson (electronic and nuclear spins are zero).

Additional background material on the Nobel Prize in Physics 1996 1996

Bosons such as helium-4 follow Bose-Einstein statistics which, among other things, means that under certain circumstances they condense in the state that possesses the least energy.

Press Release: The 1996 Nobel Prize in Physics 1996

Starting with the experience of superfluidity in helium-4 and superconductivity in metals, it was expected that the fermions in liquid helium-3 should be capable of forming boson pairs and that superfluidity should be obtainable in very cold samples of the isotope helium-3.

Press Release: The 1996 Nobel Prize in Physics 1996

As a quantum liquid helium-3 thus exhibits a considerably more complicated structure than helium-4.

Press Release: The 1996 Nobel Prize in Physics 1996