Recently ultracold lanthanide atoms such as dysprosium and erbium have attracted significant attention in many-body physics [2] and quantum simulation [3] due to their large magnetic dipole-dipole interaction (DDI) [4] and richnesss of Feshbach resonances [5]. Many exotic many-body physics phenomena were explored such as quantum droplet [6, 7], supersolid [8, 9, 10] and extended Bose-Hubbard model [11, 12]. Besides, utilizing novel atomic structure of lanthanide atoms, long-lived spin-orbit coupling (SOC) fermion [13], sythentic gauge field [14, 15] and a bilayer with 50 nm spcing [16] 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...[ Read more ]

Recently ultracold lanthanide atoms such as dysprosium and erbium have attracted significant attention in many-body physics [2] and quantum simulation [3] due to their large magnetic dipole-dipole interaction (DDI) [4] and richnesss of Feshbach resonances [5]. Many exotic many-body physics phenomena were explored such as quantum droplet [6, 7], supersolid [8, 9, 10] and extended Bose-Hubbard model [11, 12]. Besides, utilizing novel atomic structure of lanthanide atoms, long-lived spin-orbit coupling (SOC) fermion [13], sythentic gauge field [14, 15] and a bilayer with 50 nm spcing [16] 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) Bose- Einstein Condensates (BEC) [17]. The details of critical components of the apparatus will be introduced. Besides, various improvements on the apparatus will be discussed, such as two-stage slower [18, 19, 20], a cost-effective but powerful approach to enhance saturation atoms number and loading speed of a narrow magneto-optical trap (MOT), active injection locking scheme offering superior long-term stability [21], saturation fluorescence spectroscopy for narrow linewidth transition, and neural network aided detection of magnetic field for inaccessible region [22]. Furthermore, we increased the number of ¹⁶⁸Er BEC by optimizing various experimental sequence. Based on those improvements, we achieved a BEC of ¹⁶⁶Er isotope as well.

In the second part, we 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 longsought goal in the community with many novel phenomena proposed to exist. We will present our approach to the experimental characterization of dipolar bosons trapped in a quasi-2D trap. Experimentally, the 2D setup consists of an optical sheet beam to provides tight confinement, where a kinematically two-dimensional (2D) condition is satisfied [23], and a high-resolution vertical imaging system to probe in-situ density distribution. In 2D Bose gas, the Berezinskii–Kosterlitz–Thouless (BKT) crossover exist [24], and we have experimentally studied the BKT critical point, scale invariance, equation-of-state (EOS) [25, 26] and momentum distribution [27, 28] in our 2D dipolar Bose gas. To be specific, we have characterized the how DDI affect BKT critical point in the q2D dipolar Bose gas. More strikingly, we have experimentally observed anisotropy signal due to DDI in q2D BKT dipolar superfluid for the first time.