An ultra-cold Fermi gas is a great way to simulate quantum many-body physics. The deeperunderstanding of strongly interacting fermionic systems gained from studying physics of such ultra-cold systems have found applications to high TC superconductors. The apparatus described here aims to study non-equilibrium dynamics and transport properties of unitary Fermi systems by optical cooling and trapping a cloud of 6Li atoms. My contribution to the design and construction of the Sommer group ultra-cold 6Li apparatus involves the design and construction of the Feshbach resonance electronics, AOM electronics for the laser system, setup of some of the AOM and ODT optics, and some coding. In this text I describe the design of our vacuum apparatus and laser system that traps and cools 6Li atoms to micro Kelvin temperatures, characterizes its performance, and describe how it can be utilized for spin transport experiments across normal-superfluid interface
The work described in this thesis is related to various projects that I worked on towards the production of ultra-cold ensembles of ⁸⁵Rb, ⁸⁷Rb and fermionic ⁶Li. In the past few years, ultra-cold atomic gases have evolved into a mature field of research, driving various theoretical and experimental groups towards new possibilities. This thesis starts with an overview of the research direction of the field and the lab in particular, to use ultra-cold fermionic atoms as quantum simulators for several condensed matter problems. It discusses the experimental route to quantum degeneracy in a sample of ultra-cold atoms and techniques to get there. The rest of the thesis primarily discusses the first step to degeneracy- production of ultra-cold ensembles of rubidium and lithium. It starts with the theoretical concepts that enable laser cooling and trapping. The interaction between light and atoms and how it leads to a decrease in temperature of the ensemble is discussed. The limits of different cooling mechanism with relevance of the atoms of interest are described. The starting point for all laser cooling experiments is an atomic source, the details of the requirements and efficiency of different atomic sources is discussed, emphasizing our choice of sources for the two atoms. Other technical details such as the vacuum system and the control system for the experiment are briefly discussed. Preliminary data from our first ensembles of ultra-cold lithium and rubidium is shown. At the end, the planning and progress of the first experiments that we aim to achieve with these ultra-cold atoms namely looking for Feshbach resonances and studying the effect of DC electric fields on them, and studies with ultra-cold lithium atoms in optical lattices, is discussed.
Cold atom apparatuses have proven to be an invaluable tool in quantum many-body studies as they provide a platform for quantum simulations. These systems allow us to explore thousands of avenues related to neutron stars, novel technologies, quantum many-body physics and many more. Since joining the Sommer Laboratory group, I have made significant contribution to the design and construction of an ultracold 6Li apparatus. In this work I describe the design of a 'two-part' vacuum system for the injection and manipulation of lithium atoms. Additionally, I describe the lasersystems necessary to cool and capture hot lithium atoms to temperatures on the order of several hundred micro-kelvin. Finally I discuss the design and performance of our built apparatus at the time of this dissertation's submission. I will also give a brief overview of research that has led up to this point in the field of atomic physics followed by a description of our atomic apparatus and the future application of this apparatus.
This thesis presents novel techniques for the experimental study of ultracold quantum gases of fermionic lithium and potassium atoms.In the first part of this thesis, we describe the design and characterization of the new components of our experimental apparatus capable of trapping and cooling simultaneously
6Li and
40K atoms to ultracold temperatures.We report on a novel sub-Doppler cooling mechanism, operating on the D
1 line transition of alkali atoms, for laser cooling of lithium and potassium. The measured phase space densities after this molasses phase are on the order of
10−4 for both
6Li and
40K. We present the forced evaporative cooling of
40K atoms, starting in an optically plugged magnetic quadrupole trap and continuing in an optical dipole trap. In this context, we report on the production of a quantum degenerate Fermi gas of
1.5×105 atoms
40K in a crossed dipole trap with
T/TF=0.17, paving the way for the study of strongly interacting superfluids of
40K.In the second part of this thesis, we present a narrow-linewidth, all-solid-state laser source, emitting 5.2 W in the vicinity of the lithium D-line transitions at 671 nm. The source is based on a diode-end-pumped unidirectional ring laser operating on the 1342 nm transition of Nd:YVO
4, capable of producing 6.5 W of single-mode light delivered in a diffraction-limited beam. We report on three different approaches for second-haromonic generation of its output beam, namely by employing an enhancement cavity containing a ppKTP crystal, intracavity frequency doubling and a ppZnO:LN waveguide structure.
I have been one of the main responsible for building a new laboratory for Bose-Einstein condensation with 87Rb. In particular, the experimental setup has been designed for performing experiments with Bose-Einstein condensates load into optical lattices of variable geometries. All parts essential for Bose-Einstein condensation are in place. Atoms are collected in a magneto-optical trap, transferred to another vacuum chamber, with better vacuum, and trapped in another magneto-optical trap. Atoms are successfully transferred to a dark magnetic trap, and system for diagnostics with absorption imaging has been realized. We have not yet been able to form a Bose-Einstein condensate, due to a range of technical difficulties. Equipment for alignment of optical lattices with flexible geometry has been designed, built, and tested. This tool has been proven to work as desired, and there is a great potential for a range of unique experiments with Bose-Einstein condensates in optical lattices of various geometries, including superlattices and quasi-periodic lattices. Numerical studies have been made on anisotropic optical lattices, and the existence of a transition between a 2D superfluid phase and a 1D Mott-insulating phase has been confirmed. We have shown that the transition is of Berezinskii-Kosterlitz-Thouless type. In another numerical study it has been shown that using stimulated Raman transitions is a practical method for transferring atoms between states in a double optical lattice. Thus, it will be possible to transfer populations between the lattices, with further applications in qubit read/write operations.
We report on the design and construction of a versatile setup for experiments with ultracold lithium (Li) gases. We discuss our methods to prepare an atomic beam and laser cool it in a Zeeman slower and a subsequent magneto-optical trap, which rely on established methods. We focus on our laser system based on a stable interference-filter-stabilized, linear-extended-cavity diode laser, so far unreported for lithium wavelengths. Moreover, we describe our optical setup to combine various laser frequencies for cooling, manipulation, and detection of Li atoms. We characterize the performance of our system preparing degenerate samples of Li atoms via forced evaporation in a hybrid crossed-beam optical-dipole trap plus confining magnetic trap. Our apparatus allows one to produce quantum gases of N ≈ 105…106 fermionic lithium-6 atoms at nanokelvin temperatures in cycle times below 10 s. Our optical system is particularly suited to study the dynamics of fermionic superfluids in engineered optical potentials.