Most students of physics know about the special properties of Bose-Einstein condensates (BECs) as demonstrated in the two best-known examples: superfluid helium-4, first reported in 1938, 1 and condensates of trapped atomic gases, first observed in 1995. 2 (See the article by Wolfgang Ketterle in Physics Today, December 1999, page 30.) Many also know that superfluid 3 He and superconducting metals contain BECs of fermion pairs. 3 An underlying principle of all those condensed-matter systems, known as quantum fluids, is that an even number of fermions with half-integer spin can be combined to make a composite boson with integer spin. Such composite bosons, like all bosons, have the property that below some critical temperature—roughly the temperature at which the thermal de Broglie wavelength becomes comparable to the distance between the bosons—the total free energy is minimized by having a macroscopic number of bosons enter a single quantum state...
David Snoke, Peter Littlewood; Polariton condensates. Physics Today 1 August 2010; 63 (8): 42–47. https://doi.org/10.1063/1.3480075
Download citation file:
Purchase an annual subscription for $25. A subscription grants you access to all of Physics Today's current and backfile content.