Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session L3: Recent Work on Strongly Coupled Fermi Gases I |
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Sponsoring Units: DCMP Chair: Alexander Fetter, Stanford University Room: LACC 515B |
Tuesday, March 22, 2005 2:30PM - 3:06PM |
L3.00001: Fermionic Condensates Invited Speaker: The realization of fermionic superfluidity in a dilute gas of atoms, analogous to superconductivity in metals, is a long-standing goal of ultracold gas research. In my talk I will present experiments where it has become possible to create a condensate of fermionic atom pairs. These pairs are regarded as generalized Cooper pairs in the crossover regime between BCS-type superfluidity and Bose-Einstein condensation (BEC). Beyond providing experimental access to this exciting crossover regime, a gas of ultracold fermionic atoms is a highly controllable system where experimenters can widely vary interactions and study dynamical behaviour. The experiments therefore open the intriguing possibility to address fundamental questions of modern solid state physics with an atomic physics system. [Preview Abstract] |
Tuesday, March 22, 2005 3:06PM - 3:42PM |
L3.00002: Universal properties of Fermi gases near a Feshbach resonance Invited Speaker: A resonantly-interacting degenerate gas of Fermi atoms provides a paradigm for strong interactions and impacts several disciplines, including condensed matter physics (high-temperature superconductivity), nuclear physics (universal interactions, quark-gluon plasma), high-energy physics (effective theories of strong interactions), and astrophysics (neutron stars). A feature common to all of these systems is that spin-up and spin-down particles ``strongly" interact, i.e., the zero-energy scattering length far exceeds the interparticle spacing. The atomic gas is an extremely flexible experimental system: Thanks to the Feshbach resonance phenomenon, the scattering length can be tuned to any value simply by applying an external magnetic field. I will describe experiments that focus on two phenomena stemming from strong interactions: (i) high-temperature superfluidity and (ii) universality, in which the system becomes independent of the microscopic details of the interaction. These phenomena are probed by studying the fundamental thermodynamics and mechanical properties of an optically trapped gas of fermionic lithium-6. [Preview Abstract] |
Tuesday, March 22, 2005 3:42PM - 4:18PM |
L3.00003: Strongly Interacting Fermi Gases: Current Issues and Future Prospects Invited Speaker: There has been rapid development in the study of interacting atomic Fermi gases last year. In this talk, I shall discuss the issues brought forth by current experiments with regard to the nature of the newly found pair condensate, the universal thermodynamic and dynamical features in strongly interacting regime, and new methods of probing strongly interacting physics not possible in solid state environment. In the last part of the talk, I shall discuss the exciting theoretical possibilities associating with the latest experimental progress on producing molecules with higher orbital angular momentum, and on strongly interacting Fermi gases in optical lattices. \newline \newline In collaboration with Roberto Diener. [Preview Abstract] |
Tuesday, March 22, 2005 4:18PM - 4:54PM |
L3.00004: BCS-BEC crossover in strongly interacting Fermi gases Invited Speaker: We discuss our treatment of the BCS-BEC crossover for trapped Fermi atoms, where the mutual interaction can be tuned from weak to strong coupling by means of a Fano-Feshbach resonance. A simple Hamiltonian describing fermions of two different species mutually interacting with a point-contact interaction leads to an accurate description of the systems that currently are the most widely studied experimentally. The resulting many-body problem is then solved by diagrammatic methods. The superfluid phase is described by a single-particle fermionic self-energy, where it is crucial that pairing-fluctuation effects are included on top of the BCS mean-field. The theory reduces to the Popov theory for dilute superfluid fermions in weak coupling and to the Bogoliubov approximation for the composite bosons in strong coupling (where bosonic molecules form as bound-fermion pairs). Excellent agreement is found by comparing our theoretical results with experimental data on cold trapped Fermi atoms as well as with recent QMC simulations, especially in the crossover region about the unitarity limit. Further developments of the theory will be also discussed. [Preview Abstract] |
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