superfluidity

History

Discovered in 1937 by Pyotr Kapitsa (not in the list) and independently by John Allen and Don Misener. Lev Landau explained it with a quantum theory. Later, scientists understood that superfluidity is linked to the condensation of atoms into a single quantum state.

How it works

At ultra-low temperatures, helium atoms behave like one giant quantum particle (Bose-Einstein condensate), moving coherently without collisions that cause friction.

History

Discovered in 1937 by Pyotr Kapitsa (not in the list) and independently by John Allen and Don Misener. Lev Landau explained it with a quantum theory. Later, scientists understood that superfluidity is linked to the condensation of atoms into a single quantum state.

How it works

At ultra-low temperatures, helium atoms behave like one giant quantum particle (Bose-Einstein condensate), moving coherently without collisions that cause friction.

History

In 1937, Pyotr Kapitsa in Cambridge discovered almost complete disappearance of viscosity in helium-4 below 2.17 K. Simultaneously, John Allen and Don Misener observed the fountain effect. In 1941, Lev Landau built a theoretical model, introducing the concepts of superfluid and normal components. The idea of connection with Bose-Einstein condensation, predicted by Satyendra Nath Bose and Albert Einstein, was proposed by Fritz London (not in the list). Superfluidity of He-3 was discovered in 1972 by Douglas Osheroff, Robert Richardson, and David Lee, and explained via Cooper pairing with anisotropy.

How it works

Superfluidity of helium-4 is due to the bosonic nature of atoms. At low temperatures, a macroscopic fraction of atoms occupies a single quantum state — a Bose-Einstein condensate forms. Elementary excitations — phonons and rotons — define the spectrum. According to Nöther's theorem, spontaneous breaking of gauge symmetry leads to a gapless mode of oscillations, providing superfluidity. The superfluid component flows without viscosity until the velocity exceeds a critical value determined by Landau's criterion. Superfluidity in helium-3 is more complex: atoms are fermions, they form Cooper pairs, turning into bosons, which then condense. This is analogous to superconductivity but with p-wave pairing, leading to anisotropic properties.

Open problems & fun facts

The mechanism of high-temperature superfluidity (if possible) is not revealed.; The behavior of quantum turbulence in superfluid liquids is not fully understood.; Interaction of superfluid and normal components in complex geometries and in the presence of impurities.

💡 Superfluid helium does not boil in the ordinary sense: due to a thermal conductivity millions of times greater than copper, bubbles do not form, and the liquid evaporates only from the surface.