Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Deborah Jin

Second Advisor

Eric Cornell

Third Advisor

Cindy Regal

Fourth Advisor

Jun Ye

Fifth Advisor

Victor Gurarie

Abstract

The nature of the normal phase of an ultracold Fermi gas in the BCS-BEC crossover regime is an interesting and unresolved question. As interactions increase, while the many-body ground state remains a condensate of paired fermions, the normal state must evolve from a Fermi liquid to a Bose gas of molecules. In this thesis, I present a technique to spatially select a homogeneous sample from the center of a trapped gas to explore this crossover. Combining this technique with RF spectroscopy, we locally measure Tan's contact as a function of temperature and compare to various many-body theories. In another experiment, we measure the distribution of single-particle energies and momenta for a normal gas across the BCS-BEC crossover. We find that the data fit well to a two-part function that includes a peak corresponding to fermionic quasiparticles and an "incoherent background" that is modeled using the dispersion of thermal molecules. I also describe the construction of a new-generation Fermi gas apparatus.

Comments

Sixth advisor: Carl Lineberger.

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