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Experiments with Degenerate Bose and Fermi Gases
| Content Provider | Semantic Scholar |
|---|---|
| Author | Gupta, Subhadeep |
| Copyright Year | 2003 |
| Abstract | Two sets of studies are described in this thesis. In the first set, an atom interferometry technique was developed for the measurement of the fine structure constant using a BoseEinstein Condensate. In the second set, degenerate Fermi gases were prepared and their properties explored in a regime of strong interactions. We have developed an atom interferometer which is capable of measuring with high precision the “photon recoil frequency” (ωrec). ωrec corresponds to the kinetic energy of an atom recoiling due to absorption of a photon. ωrec can be used to determine the quantity h/matom and the fine structure constant, α. A preliminary measurement using a 23Na BoseEinstein Condensate yielded ωrec with a precision of 7 × 10−6 which deviated by 2 × 10−4 from the currently accepted value. Plausible upgrades to the apparatus should produce a precision of 10−9 which would bring within reach a measurement of h/matom and α in the 10−9 range. Such accuracy would be of considerable scientific and metrological import. A quantum degenerate gas of 6Li fermions was produced by sympathetic cooling with 23Na bosons in a two-species atom trapping apparatus. The cooling strategy was optimized to enable production of fermions with atom numbers up to 7 × 107 at half the Fermi temperature (TF ), or temperatures down to 0.05TF ∼ 100 nK with 3× 107 atoms. We can also produce degenerate Bose-Fermi mixtures with several million atoms in each species. We studied the behavior of mixtures of fermi gases in regimes of strong interactions near “Feshbach” resonances. A study of system stability enabled the experimental observation of two such Feshbach resonances. We carried out a theoretical study to interpret the observation (by many experimental groups) of hydrodynamic behavior of fermi gases during expansion out of an atom trap in a strongly-interacting regime. The study concluded that this behavior was not a qualitative signature of fermionic superfluidity and could arise from classical collisions. Finally, radio-frequency (RF) spectroscopy was used to probe interaction in 6Li. We demonstrated the absence of mean field “clock” shifts of RF transitions in a two-(spin)state fermion system. Using a three-state system, we measured the interaction strength between different spin states. The measurements near Feshbach resonances indicate a saturation of the interaction strength at a large negative value. This result is of relevance in the continuing quest for fermionic superfluidity in atomic gases. Thesis Supervisor: David E. Pritchard Title: Cecil and Ida Green Professor of Physics Thesis Supervisor: Wolfgang Ketterle Title: John D. MacArthur Professor of Physics |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.rle.mit.edu/cua_pub/ketterle_group/Theses/Thesis_Deep.pdf |
| Alternate Webpage(s) | http://cua.mit.edu/ketterle_group/Theses/Thesis_Deep.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
