Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 24: Symposium “Condensed Matter Phases in Ultracold Atoms”

TT 24.6: Talk

Thursday, March 29, 2007, 12:00–12:25, H20

Fermionic Superfluidity with Imbalanced Spin Populations — •Martin Zwierlein — MIT, Cambridge, MA, USA — Johannes-Gutenberg Universität Mainz, Germany

Whether it occurs in superconductors, helium-3 or inside a neutron star, fermionic superfluidity requires pairing of fermions. For an equal mixture of spin up and spin down fermions, pairing can be complete and the entire system will become superfluid. If the two fermion populations are imbalanced, not every particle can find a partner. Will the system nevertheless stay superfluid?

In this talk I will present our studies of this intriguing question in an unequal mixture of strongly interacting, ultracold fermionic atoms. We establish the phase diagram for the superfluid and the normal state as a function of population imbalance and interaction strength. Due to strong interactions near a Feshbach resonance, the superfluid state is remarkably stable in response to population imbalance. The final breakdown of superfluidity at large imbalance marks a phase transition, the Pauli or Clogston limit of superfluidity.