Ultracold gases of fermionic atoms offer researchers a way to study quantum many-body phenomena using measurement techniques from atomic and molecular physics. In a new experiment, Hauke Biss of the University of Hamburg, Germany, and colleagues have used such a gas to measure the excitation spectrum of a quantum many-body system that undergoes a transition from a Bose-Einstein condensate (BEC) to a Bardeen-Cooper-Schrieffer (BCS) superfluid [1]. The results provide important benchmark data for theories of strongly interacting Fermi gases in settings such as neutron stars and unconventional superconductors.
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