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Ultracold Fermions with Repulsive Interactions and Bragg Scattering in an Optical Lattice

Event Details

Event Dates: 

Wednesday, August 29, 2012 - 10:00am

Speaker Name(s): 

Wolfgang Ketterle

Speaker Affiliation(s): 

John D. MacArthur Professor of Physics, MIT-Harvard Center for Ultracold Atoms, MIT
Seminar Type/Subject

Event Details & Abstract: 

For a gas of fermions with repulsive interactions, a transition to a ferromagnetic phase has been predicted – the so-called Stoner model for itinerant ferromagnetism. However, any strong short-range repulsive potential necessarily features a weakly bound paired state. Our experiments show that the ferromagnetic transition does not take place, but is rather preempted by rapid pair formation. Our experimental study can be regarded as a quantum simulation of a Hamiltonian, for which even the qualitative phase diagram cannot be reliably obtained by computational methods. Second, I will show how light scattering can reveal the structure of atoms in optical lattices, analogous to X-ray or neutron scattering off solids.