Physics Dissertation Defense: Yunpeng Ji, Yale University, “ ‘Many-Body Physics in an Ultracold Uniform Fermi Gas”

Event time: 
Friday, October 27, 2023 - 2:00pm to 3:00pm
Sloane Physics Laboratory SPL, Room 56 See map
217 Prospect Street
New Haven, CT 06511
Yunpeng Ji, Yale University
Event description: 

Ultracold atomic gases, traditionally produced in harmonic traps, have been a successful platform in studying many-body problems. Recent developments in homogeneous quantum gases in optical box potentials have introduced new opportunities for investigating complex problems without the complications arising from the density inhomogeneity, enabling more straightforward comparisons with theories. In this presentation, I will introduce the production of a uniform Fermi gas composed of Li-6 atoms and outline four projects that leverage this pristine experimental environment: (I) Stability of the repulsive Fermi gas with contact interactions. We identify that the primary decay mechanism of the gas is a universal three-body recombination process towards the formation of Feshbach molecules. (II) Fermionic Joule-Thomson effect. We investigate the temperature dynamics of a homogeneous Fermi gas during isenthalpic rarefaction. (III) Decay of a strongly interacting Fermi gas. We observe exponential decay of the gas in the BEC-BCS crossover and explore the effect of light on atom losses. (IV) Excitation and observation of sound waves in degenerate Fermi gases. We observe the emergence of sound in a Fermi liquid, and investigate the acoustic response beyond the linear response regime in both the weakly and strongly interacting Fermi gases.

Committee members:
Nir Navon (advisor), Yoram Alhassid, Leonid Glazman, Jack Harris, Frédéric Chevy and Joseph Thywissen