Abstract
Recently ultracold lanthanide atoms such as dysprosium and erbium have attracted significant attention in many-body physics [3] and quantum simulation [4] due to their large magnetic dipole-dipole interaction (DDI) [5] and richnesss of Feshbach resonances [6]. Many exotic many-body physics phenomena were explored such as quantum droplet [7, 8], supersolid [9, 10, 11] and extended Bose-Hubbard model [12, 13]. Besides, utilizing novel atomic structure of lanthanide atoms, long-lived spin-orbit coupling (SOC) fermion [14], sythentic gauge field [15, 16] and a bilayer with 50 nm spcing [17] were created. However, realizing quantum degeneracy of lanthanide atoms remains challenging because of the high operating temperature of the oven for generating sufficient atomic flux, narrow linewidth of optical cooling transition, stability of magnetic field, and so on.
The first part of this thesis will present a newly-built apparatus for Erbium (Er) BoseEinstein Condensates (BEC) [18]. The details of important components of the apparatus will be introduced. Besides, various improvements on the apparatus will be included, such as two-stage slower [19, 20, 21], a cost-effective but powerful approach to enhance satuxiv LIST OF TABLES ration atoms number and loading speed of a narrow magneto-optical trap (MOT), active injection locking scheme offering supreme long-term stability [22], saturation fluorescence spectroscopy for narrow linewidth transition, and neural network aided detection of magnetic field for inaccessible region [23]. Furthermore, enhancement of BEC atoms number is achieved via optimization of experimental sequence. Based on this, BEC of 166Er isotope can be generated with the same atom number as 168Er.
The second part will present the realization and study of a quasi-two-dimensional dipolar (q2D) Bose gas with our erbium apparatus. Quasi-2D dipolar Bose gas is a long-sought goal in the community with many novel phenomena proposed to exist. The work of the thesis detailed the first experimental study with ultracold Er atoms and try to establish a framework, pure 2D model, in the slightly dipolar regime using 168Er. Experimentally, the 2D setup consists of an optical sheet beam to provides tight confinement, where a kinematically two-dimensional (2D) condition is satisfied [24], and a high-resolution vertical imaging system to probe in-situ image. In 2D Bose gas, the Berezinskii–Kosterlitz–Thouless (BKT) crossover exist [25], and we have experimentally studied the scale invariance, equation-of-state (EOS) [26, 27] and momentum distribution [28, 29] in our 2D dipolar Bose gas. We have observed the effect from DDI on the properties of 2D dipolar Bose gas and will discuss in the thesis.