In this thesis we study and characterize an erbium atomic beam emerging from a high-temperature oven system. This is the first step towards the production of a quantum-degenerate gas of Er. Er is a rare-earth element and its quantum mechanical interaction properties are yet rather unexplored. Its exceptionally large magnetic moment of 7μB makes Er especially interesting, since it allows studies on the physics of dipolar quantum gases. In addition, Er shows an unusual electronic configuration and a complex energy level scheme, promising rich scattering properties and offering many possibilities for laser cooling. Since Er has a high melting point temperature of more than 1500 C, the oven system for the production of a thermal atomic beam requires specific engineering. This includes thermal shielding, heated apertures, special crucible materials as well as reliable controland security systems. We characterize the atomic beam emerging from the oven by absorption spectroscopy and fluorescence imaging on the strong 401 nm transition. Based on our measurements, we optimize the collimation setup and we find the ideal operation temperature to be T ≃ 1250 C with a corresponding atomic flux of 3× 1010 s−1 injected into the Zeeman slower.
In this thesis we study and characterize an erbium atomic beam emerging from a high-temperature oven system. This is the first step towards the production of a quantum-degenerate gas of Er. Er is a rare-earth element and its quantum mechanical interaction properties are yet rather unexplored. Its exceptionally large magnetic moment of 7μB makes Er especially interesting, since it allows studies on the physics of dipolar quantum gases. In addition, Er shows an unusual electronic configuration and a complex energy level scheme, promising rich scattering properties and offering many possibilities for laser cooling. Since Er has a high melting point temperature of more than 1500 C, the oven system for the production of a thermal atomic beam requires specific engineering. This includes thermal shielding, heated apertures, special crucible materials as well as reliable controland security systems. We characterize the atomic beam emerging from the oven by absorption spectroscopy and fluorescence imaging on the strong 401 nm transition. Based on our measurements, we optimize the collimation setup and we find the ideal operation temperature to be T ≃ 1250 C with a corresponding atomic flux of 3× 1010 s−1 injected into the Zeeman slower.
Atomic oven generating controllable atomic beam flux plays a fundamental role in quantum gas experiments. Here, we report a new heater design that can heat up an high temperature atomic oven with fast thermal response. The new heater shows a heating rate improved by 7.65 times comparing to that of the conventional resistive heater while the crucible temperature can heated up to 1200K. With this oven, we generated a collimated ytterbium beam with flux exceeding 1014 atoms/s at 823 K. We believe that our design offers a promising solution for shortening experimental dead time and improve the experiment efficiency in cold atom researches.
Ultracold atoms are powerful platforms through which to study many-body physics. In recent years there has been a marked increase in the number and variety of species (lanthanides, transition metals, dipolar molecules, etc.) brought to ultracold temperatures, providing new ingredients from which to build interesting systems. In this thesis I report on the design and construction of an erbium-lithium mixture apparatus with broad applicability for quantum simulation. The combination of large mass imbalance, competition of interaction length scales, and variable quantum statistics points toward this mixture hosting a rich variety of Bose-Bose and Bose-Fermi phases with applications ranging from condensed matter to astrophysics. Leveraging these desirable properties, however, necessitated the development of a new quantum gas platform. The first section of this thesis is dedicated to describing that process in detail. The second section of this thesis describes the development of experimental sequences through which we synthesize quantum gases. In our experiments we successively laser cool each species before combining them in a suite of optical dipole traps for evaporative cooling to degeneracy. I finally present our creation of the first degenerate Bose-Bose mixture of erbium-166 and lithium-7, as well as a measurement of the interspecies s-wave scattering length.
Quantum gas microscopy provides an exciting platform for the study of in situ atom-atom interactions. Recent advances in quantum gas microscopy have allowed the probing of the Bose-Hubbard and Fermi-Hubbard Hamiltonian with a variety of atomic species. In this thesis, we are currently extending these platforms with the introduction of an Erbium Dipolar Quantum Gas Microscope which will allow us to study dipole-dipole interactions in a lattice. Erbium has several exciting properties, which increase the control and flexibility of these systems. These include stable bosonic and fermionic isotopes, a large magnetic dipole moment (7uB), a large spin value (J=6 and F=19/2 for bosonic and fermionic isotopes), a rich Feshbach spectrum, and several useful broad and narrow atomic transitions. A broad 401 nm transition can be used for imaging, which in combination with a 266 nm lattice spacing will provide fast time scales and access to a dipole-dipole interaction of approximately 30 Hz. This thesis will document the progress toward an Erbium Quantum Gas Microscope and include a variety of systems which have been developed. It will also show the first ever 841nm, red-detuned Magneto-Optical Trap with temperatures as low as 400 nK and a phase space density up to 0.05. This, in combination with other improvements, will allow for faster cycle times and more control over the system. These developments will allow us to benefit from the long-range interaction of Erbium and probe the Extended Bose-Hubbard and Extended Fermi-Hubbard Hamiltonian to an unprecedented degree.
With the advent of ultracold atomic gases experimentally realized by laser cooling techniques nearly 40 years ago, the doors to accessing novel physical behaviour have been opened wide and far. Experimentally, research in this domain started with alkali atoms, proceeded with alkaline earth atoms, and only more recently embarked on atoms with higher complexity of their spectrum, as e.g. the highly dipolar lanthanide atomic species erbium and dysprosium. Those elements possess a non-vanishing orbital angular momentum in the ground state, leading to ample advantages for the manipulation with far-detuned laser light in phase imprinting schemes, as losses due to spontaneous scattering can be suppressed radically in comparison to the case of alkali atomic species. This beneficial behaviour will be used in the future for the generation of synthetic magnetic fields for electrically neutral erbium atoms aimed at investigating fractional quantum Hall physics. This thesis describes in the first part the generation of an atomic erbium Bose-Einstein condensate in a hybrid crossed optical dipole trap. The main purpose of this endeavor was an enhancement of absolute atom number of the degenerate ensemble and long-term stability of the experimental setup with respect to the use of a single beam dipole trap. A comparison of the here achieved results with respect to those achieved in only a single CO2 laser beam dipole trap is illustrated. In the second part of this thesis a theoretical evaluation of the generation of synthetic magnetic fields for ultracold erbium atoms in prospect for experimental investigations of fractional quantum Hall physics is presented. One of the most promising techniques for the realization of strong synthetic magnetic fields is by phase imprinting via Raman manipulation. Here for the theoretical calculation of such fields with erbium atoms a compared to earlier work on alkali atoms new modified optical Raman coupling scheme in a σ+ - σ- beam polarization configuration is chosen. It is shown that sufficiently high field strengths with good spatial homogeneity can be reached for experimentally viable parameters. Additionally, an estimation for the expected Laughlin gap in the proposed erbium atomic fractional quantum Hall system is given.
Simulating highly correlated quantum systems with classical computers exceed their capa- bilities as the system size increases. In analog quantum simulators, the system of interest is mimicked by another quantum system in a highly controllable and accessible environ- ment. Even though quantum simulations with ultracold atoms have been demonstrated successfully, ultra-low temperature regimes are experimentally challenging to achieve and still remain to be explored. New approaches to realizing ever lower temperatures, especially in Fermi systems, have been and continue to be a constant pursuit in Atomic, Molecular, and Optical Physics (AMO). Within this thesis, a new quantum gas experiment of fermionic 6Li and bosonic 166Er is presented and first results on sympathetic cooling of Li to quantum degeneracy by Er are demonstrated. The experimental apparatus is described in detail with a focus on the Li subsystem of the dual-species experiment. Standard and further developed laser cooling techniques used to produce a Magneto-Optical Trap (MOT) of Li are characterized, along with their associated vacuum system stages. In this context, a combined Optical Pumping / Transversal Cooling (OP/TC) technique of the atomic beam on the D1-line is presented, and an enhancement of the MOT loading rate by one order of magnitude is demonstrated. The architecture and building blocks of the laser system for providing resonant light at 671 nm for laser cooling of Li are detailed, and laser locking techniques for frequency stabilization and light amplification by injection locking of high-power laser diodes are presented. Special focus is placed on the introduction and characterization of a new laser- diode-independent injection locking technique, keeping spectrally pure amplified light by a periodic slave current optimization routine executed by a microcontroller. The system has been submitted for patent approval. In further steps of optical cooling of Li, a non-standard free-space Gray Molasses (GM) technique based on intensity ramps, providing temperatures as low as 13 µK, is presented. The non-standard technique is characterized and compared to the standard pulse GM approach, which typically achieves 50 µK only. Cooling steps for preparing an ultracold Li cloud in the glass cell start from an Optical Dipole Trap (ODT) loaded by a compressed Magneto-Optical Trap (cMOT) and consecutive evaporation into a 1D transport lattice of counter propagating 1064 nm laser beams. By detuning one of the lattice beams, optical transport over 1 m to the glass cell with an efficiency of 74% is demonstrated. In a combined ErLi sequence, the two species are transported to the glass cell together and loaded to 1064 nm ODTs. Sympathetic cooling of Li by forced evaporation of Er to T/TF = 0.77 ± 0.10 next to the production of an Er BEC are presented. To conclude, this work introduces a new promising dual-species quantum gas experiment and its ability for providing sympathetic cooling of Li by Er to quantum degeneracy is demon- strated. These findings are an encouraging foundation for achieving higher degeneracies by refined experimental control in pursuit of penetrating unexplored temperature regimes in quantum simulators.
If a beam is to be produced from a material that is solid or liquid at laboratory temperature, then it must be converted to a vapour in an oven before it passes through the beam-forming impedance. In the reviews mentioned in Section 1.2, the approach has usually been to give details of numerous designs. In this chapter, we discuss the general design principles, and then the next two chapters become more of a reference source for the evaporation of different substances. We thus include the experience of a large number of experimenters who have needed to heat a liquid or solid substance to form it into an atomic or molecular beam. If the material can be evaporated and raised to a temperature to give the required input pressure at the input to the impedance at a temperature less than about 1500 K, it is usual to describe the heating device as an oven. At higher temperatures, the device is usually called a furnace, but the distinction is not really necessary. Hence we will avoid the term except for thermal dissociation of a molecular species, discussed in Chapter 6, when very high temperatures are usually needed, so a furnace is a more appropriate term. For convenience we will also term a completely different approach, namely, the evaporation of the material by direct electron beam heating of the surface (Section 3.2.5) as an oven. ‘Crucible’ is used by many authors interchangeably with ‘oven,’ but it often implies a container for the material to be evaporated that is placed within a heated envelope.