Bose-Fermi mixtures of ultracold gases of dysprosium

Laser cooling and trapping of the most magnetic fermionic atom, dysprosium (Dy), may provide a framework to explore quantum liquid crystal (QLC) theory (Chapter 1). This thesis presents details of the Dy laser cooling and trapping apparatus including the laser systems at 421, 741, and 1064 nm, the ultra-high vacuum (UHV) chamber, and the computer control that has produced a magneto-optically (MOT) and magneto-statically (MT) trapped Dy gas (Chapters 3, 4, 5). Despite the fact that Dy has a complex energy level structure with nearly 140 metastable states (Chapter 2), Dy MOT at 421-nm transition with 32-MHz linewidth was realized without any rempumper, exploiting its large magnetic moment, which brought a strong magnetic confinement of metastable states of Dy. This unique MOT/MT dynamics is discussed and its quantitative measurements are shown in Chapter 6. When the Dy atoms dropped from the MOT were adsorptively imaged, it was observed that Dy MOT had a bimodal temperature distribution in contrast to the usual MOT described by a single temperature (Chapter 7). Such novel anisotropic sub-Doppler laser cooling of Dy, which breaks the symmetry in cooling, is due to Dy's large magnetic spin aligned along a strong axis of the quadrupole field of the MOT, and we further support this plausible conjecture with the velocity selective resonance (VSR) theory. The MOT at ~ 1 mK was cooled to ~ 10 uK by narrow-line cooling at 741 nm with a linewidth of 2 kHz, and we were able to load the optical dipole trap (ODT) at 1064 nm. By loading two isotopes of 164Dy and 163Dy in sequence to the MOT and narrow-line cooling them simultaneously, ultracold Bose-Fermi mixtures of Dy in the ODT were realized (Chapter 8). This thesis is concluded with a discussion of prospect on the Bose-Fermi mixtures of Dy