Little Big Bang: Strong Interactions in Ultracold Fermi Gases

Martin Zwierlein

Massachusetts Institute of Technology

“Fermions, particles with half-integer spin such as electrons, protons and neutrons, are the building blocks of matter. Strong interactions among them give rise to novel states of matter whose properties are often not fully understood. High-temperature superconductors, neutron stars and the quark-gluon plasma of the early universe provide famous examples. Ultracold Fermi gases of atoms are a new type of strongly interacting fermionic matter that can be created and studied in the laboratory with exquisite control.

In equilibrium, direct absorption images of the trapped atomic gas reveal the entire thermodynamics of the system, including the transition into the superfluid state. The specific heat of the gas displays a characteristic lambda-like feature at the superfluid critical temperature of 17% of the Fermi temperature. Scaled to the density of electrons, superfluidity would occur far above room temperature.

Non-equilibrium processes are observable in real time. We recently studied the collision of "spin up" and "spin down" Fermi gases with resonant, quantum limited interactions, as well as the propagation of topological excitations, solitary waves, in the superfluid phase. Our measurements in and out of equilibrium provide benchmarks for current many-body theories and will help to understand other strongly interacting Fermi systems, such as high-temperature superconductors and neutron stars.”



Physics, COS