M.Sc Thesis


M.Sc StudentMenashes Meny
SubjectCharacterization of a Uniform Fermi Gas
using Raman Spectroscopy
DepartmentDepartment of Physics
Supervisor ASSOCIATE PROF. Yoav Sagi
Full Thesis textFull thesis text - English Version


Abstract

In recent years, ultracold Fermi gases were proven to be a powerful platform for advancing quantum technologies and discovering rich many-body physics. The information regarding properties of these systems is often hidden in their momentum distribution, emphasizing the importance of measuring this quantity directly. We perform Raman spectroscopy in which the atoms undergo stimulated absorption and emission of two-photons. In this process, their momentum and energy are changed, which provides a new degree of freedom we control through the Raman beams. The significant momentum imprint of the Raman process allows us to probe the atoms momentum distribution and study some of its novel characteristics. In addition, we apply a dynamical decoupling scheme to flatten the confining potential experienced by the atoms. Using this sequence, we generate an atomic ensemble with a spatially uniform density and probe observables such as the condensed fraction without complications arising from varying thermodynamic conditions across the cloud. Theoretically, we show that the periodic driving leaves the interaction Hamiltonian invariant and does not heat the atomic ensemble. By applying Raman spectroscopy, we measure the momentum distribution of the driven gas, demonstrating that it follows the prediction for a uniform Fermi-Dirac distribution. From the momentum distribution, we extract the gas temperature, thus verifying that it is below the superfluid transition. By repeating this measurement with an increasing duration of the driving pulse, we directly verify that the heating of the gas by the drive is negligible in our experimental timescales. Finally, we present Raman spectra acquired with a uniform strongly interacting Fermi gas throughout the BCS-BEC crossover.