115 research outputs found
Collisional stability of a three-component degenerate Fermi gas
We report on the creation of a degenerate Fermi gas consisting of a balanced
mixture of atoms in three different hyperfine states of Li. This new system
consists of three distinguishable Fermions with different and tunable
interparticle scattering lengths , and . We are able
to prepare samples containing atoms in each state at a
temperature of about nK, which corresponds to . We
investigated the collisional stability of the gas for magnetic fields between 0
and 600 G and found a prominent loss feature at 130 G. From lifetime
measurements we determined three-body loss coefficients, which vary over nearly
three orders of magnitude
Mapping the Two-Component Atomic Fermi Gas to the Nuclear Shell-Model
The physics of a two-component cold fermi gas is now frequently addressed in
laboratories. Usually this is done for large samples of tens to hundreds of
thousands of particles. However, it is now possible to produce few-body systems
(1-100 particles) in very tight traps where the shell structure of the external
potential becomes important. A system of two-species fermionic cold atoms with
an attractive zero-range interaction is analogous to a simple model of nucleus
in which neutrons and protons interact only through a residual pairing
interaction. In this article, we discuss how the problem of a two-component
atomic fermi gas in a tight external trap can be mapped to the nuclear shell
model so that readily available many-body techniques in nuclear physics, such
as the Shell Model Monte Carlo (SMMC) method, can be directly applied to the
study of these systems. We demonstrate an application of the SMMC method by
estimating the pairing correlations in a small two-component Fermi system with
moderate-to-strong short-range two-body interactions in a three-dimensional
harmonic external trapping potential.Comment: 13 pages, 3 figures. Final versio
Crossovers in Unitary Fermi Systems
Universality and crossover is described for attractive and repulsive
interactions where, respectively, the BCS-BEC crossover takes place and a
ferromagnetic phase transition is claimed. Crossovers are also described for
optical lattices and multicomponent systems. The crossovers, universal
parameters and phase transitions are described within the Leggett and NSR
models and calculated in detail within the Jastrow-Slater approximation. The
physics of ultracold Fermi atoms is applied to neutron, nuclear and quark
matter, nuclei and electrons in solids whenever possible. Specifically, the
differences between optical lattices and cuprates is discussed w.r.t.
antiferromagnetic, d-wave superfluid phases and phase separation.Comment: 50 pages, 15 figures. Contribution to Lecture Notes in Physics
"BCS-BEC crossover and the Unitary Fermi Gas" edited by W. Zwerge
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