What is Bose-Einstein condensation a phase of?

Bose-Einstein condensation is a phase of matter that occurs at extremely low temperatures, close to absolute zero, where a group of bosons occupy the same quantum state, leading to remarkable physical phenomena. At these low temperatures, the thermal energy is minimal, allowing particles, specifically bosonic atoms, to clump together and behave collectively as a single quantum entity. This results in the formation of a superfluid state, characterized by frictionless flow and other unique properties.

The term "gaseous superfluid" is particularly appropriate because Bose-Einstein condensates form from a dilute gas of atoms that, at ultra-low temperatures, transition into the condensed phase. In this phase, the particles exhibit macroscopic quantum phenomena, which are not observable in the classical regime.

Understanding this phase transition helps to elucidate the behaviors of quantum systems and the underlying principles of quantum mechanics.