⁸⁷Rubidium Bose-Einstein condensates in optical lattices

Abstract

Bose-Einstein condensates in optical lattices have proven to be a powerful tool for studying a wide variety of physics. In this thesis a series of experiments using optical lattices to manipulate 87Rb Bose-Einstein condensates are described. A systematic shift of the photon recoil momentum due to the index of refraction of a dilute gas of atoms has been observed. The recoil frequency was measured interferometrically using a two-pulse Ramsey interferometer. The two pulses were created using a one dimensional optical lattice. By measuring the resulting frequency as a function of the lattice detuning from the atomic resonance, we found a distinctive dispersive shape for the recoil frequency that fit the recoil momentum as n,.hk. A one-dimensional optical lattice was used to modify the dispersion relation of the condensate in order to demonstrate the matter-wave analogue of Optical Parametric Generation (OPG) and Amplification (OPA) of photons. A condensate was loaded into a moving optical lattice with adjustable quasimomentum k0. As the value for k0o was varied, we observed elastic scattering into two distinct final momentum states k1 and k2.

(cont.) When a small fraction of atoms was first transferred to k1 before ramping on the lattice, we observed the amplification of scattered atoms into k1 and k2. The superfluid-Mott Insulator transition was studied using microwave spectroscopy in a deep three-dimensional optical lattice. Using the density dependent clock shift we were able to spectroscopically distinguish sites with different occupation numbers, and to directly image sites with occupation number from 1 to 5, revealing the shell structure of the Mott Insulator phase.