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• PUBLIC
  LECTURE

• Department of Physics
• Brown University
• Box 1843
• Barus Holley Building
• 182 Hope Street
• Providence, RI 02912
• physics @ physics.brown.edu

The BCS Theory of
Superconductivity

Wolfgang Ketterle
John D. MacArthur Professor of Physics
MIT

Recipeint of the 2001 Nobel Prize in together with Eric Allin Cornell and Carl Wieman. Professor of Physics Emeritus for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates.

Prof Ketterle's Wikipedia Entry
Prof Ketterle's Faculty page, MIT


Lecture
"Superfluidity and BEC-BCS Crossover in an Ultracold Gas of Fermionic Atoms"

Abstract
Ultracold quantum degenerate Fermi gases provide a remarkable opportunity to study strongly interacting fermions. In contrast to other Fermi systems, these gases have low densities and their interactions can be precisely controlled over an enormous range. A major goal has been the realization of superfluidity in such a system. The observation of vortex lattices in a strongly interacting rotating Fermi gas provides definitive evidence for superfluidity. By varying the binding energy between fermion pairs, we have studied the crossover from a Bose-Einstein condensate of molecules to a Bardeen-Cooper-Schrieffer superfluid of loosely bound pairs. The crossover is associated with a new form of superfluidity for which the observed transition temperatures (normalized for the density of the gas) by far exceed the highest transition temperatures achieved in high-T_c superconductors. We have extended those studies to fermions in optical lattices and to Fermi gases with imbalanced spin populations. The imbalanced system shows rich features including a quantum phase transition at a critical imbalance, which is the Pauli limit of superfluidity, and phase separation.