Observation of a superradiant quantum phase transition in an intracavity degenerate Fermi gas

Abstract

Fermionic superradiance Placing an atomic gas inside an optical cavity can have profound effects, for example, inducing long-range atomic interactions through the coupling with the cavity’s photons. Such experiments have been done with bosonic atoms but realizing them with fermions has proven trickier. Zhang et al . placed an ultracold gas of fermionic lithium-6 atoms in a cavity pumped by a laser beam orthogonal to the cavity axis. For sufficiently strong pumping, the researchers detected a checkerboard pattern in the atoms’ momentum space corresponding to a superradiant phase transition in the cavity. The Pauli exclusion principle, which applies to fermions but not bosons, slowed down the atomic dynamics. —JS