Revealing the Superfluid Lambda Transition in the Universal Thermodynamics of a Unitary Fermi Gas

Abstract

Nailing Down the Superfluid Transition A gas of fermions, the class of particle that protons, neutrons, and electrons belong to, can be found in contexts as different as neutron stars and a block of metal. When the interaction between fermions is on the brink of forming fermion pairs, the thermodynamics of the gas become dependent only on the gas temperature and density. Ku et al. (p. 563 , published online 12 January; see the Perspective by Zwerger ) measured this universal thermodynamics with high precision in an ultracold Fermi gas, observing the predicted transition into a superfluid state through the characteristic lambda-shaped transition in the gas's specific heat.