Atomic, Molecular, and Optical Physics Seminar

Fermionic Superfluidity with Imbalanced Spin Populations and the Quantum Phase Transition to the Normal State

Christian Schunck
Department of Physics
M I T

Whether it occurs in superconductors, helium-3 or inside a neutron star, fermionic superfluidity requires pairing of fermions. For an equal mixture of two states of fermions, pairing can be complete and the entire system will become superfluid. When the two populations of fermions are unequal, not every particle can find a partner. Will the system nevertheless stay superfluid? We studied this intriguing question in an unequal mixture of strongly interacting ultracold fermionic atoms. The superfluid region vs population imbalance was mapped out by employing two complementary indicators: The presence or absence of vortices in a rotating mixture, as well as the fraction of condensed fermion pairs in the gas. Due to the strong interactions near a Feshbach resonance, the superfluid state is remarkably stable in response to population imbalance. The final breakdown of superfluidity marks a new quantum phase transition, the Pauli limit of superfluidity.

Monday, February 27, 2006
4:00pm
Gant Science Complex
Physics Department
Room P121


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