We report the Bose-Einstein condensation (BEC) of the most magnetic element, dysprosium. The Dy BEC is the first for an open f -shell lanthanide (rare-earth) element and is produced via forced evaporation in a crossed optical dipole trap loaded by an unusual, blue-detuned and spinpolarized narrow-line magneto-optical trap. Nearly pure condensates of 1.5×10 4 164 Dy atoms form below T = 30 nK. We observe that stable BEC formation depends on the relative angle of a small polarizing magnetic field to the axis of the oblate trap, a property of trapped condensates only expected in the strongly dipolar regime. This regime was heretofore only attainable in Cr BECs via a Feshbach resonance accessed at high magnetic field.

Ultracold dysprosium gases, with a magnetic moment ten times that of alkali atoms and equal only to terbium as the most magnetic atom, are expected to exhibit a multitude of fascinating collisional dynamics and quantum dipolar phases, including quantum liquid crystal physics. We report the first laser cooling and trapping of half a billion Dy atoms using a repumper-free magneto-optical trap (MOT) and continuously loaded magnetic confinement, and we characterize the trap recycling dynamics for bosonic and fermionic isotopes. The first inelastic collision measurements in the few partial wave, 100 µK-1 mK, regime are made in a system possessing a submerged open electronic f-shell. In addition, we observe unusual stripes of intra-MOT < 10 µK sub-Doppler cooled atoms.PACS numbers: 37.10. De, 37.10.Gh, 37.10.Vz, 71.10.Ay Ultracold gases of extraordinarily magnetic atoms, such as dysprosium, offer opportunities to explore strongly correlated matter in the presence of the longrange, anisotropic dipole-dipole interaction (DDI). Such interactions in the presence (or absence) of polarizing fields can compete with short-range interactions to induce phases beyond those described by the nearest neighbor Hubbard model [1]. Specifically, quantum liquid crystal (QLC) physics (see Ref.[2] and citations within) describes strongly correlated systems in which a Fermi surface can spontaneously distort (nematics) or cleave into stripes (smectics) [3]. While material complexity can inhibit full exploration of QLC phases in condensed matter, QLC phases may be more extensively characterized in tunable ultracold gases. In contrast to ultracold ground state polar molecules [4], ultracold Dy offers the ability to explore the spontaneously broken symmetries inherent in QLCs since the DDI is realized without a polarizing field. An exciting prospect lies in observing spontaneous magnetization in dipolar systems, e.g., the existence of a quantum ferro-nematic phase in ultracold fermionic Dy gases not subjected to a polarizing field [5].We report the first magneto-optical trap (MOT) and ultracold collisional rates of this highly complex atom. The stable atoms possessing the largest magnetic moments are the neighboring lanthanide rare-earths, Tb and Dy (both 10 Bohr magnetons (µ B ) to within 0.6% [6,7]). Prior to the present work, the coldest Dy temperatures were achieved via buffer gas and adiabatic cooling to 50 mK with final densities of < 10 9 cm −3 [8], and Dy beams have been transversely pushed and unidirectionally cooled via photon scattering [9,10].Recent experiments using degenerate 52 Cr, a bosonic S-state atom with 6 µ B of magnetic moment, have begun to explore quantum ferrofluids [12]. With suitable scattering lengths, the larger magnetic moment-and 9× larger DDI·mass ratio-of Dy should allow experimental access beyond the superfluid and Mott insulator regions of the extended Bose-Hubbard phase diagram to the density wave and supersolid regimes [13]. Co-trapping iso- In addition, ultracold samples of Dy will aid precision measure...

Magneto-optical traps (MOTs) of highly magnetic lanthanides open the door to explorations of novel phases of strongly correlated matter such as lattice supersolids and quantum liquid crystals. We recently reported the first MOTs of the five high abundance isotopes of the most magnetic atom, dysprosium. Described here are details of the experimental technique employed for repumper-free Dy MOTs containing up to half a billion atoms. Extensive characterization of the MOTs' properties---population, temperature, loading, metastable decay dynamics, trap dynamics---is provided.Comment: 13 pages, 12 figures, follow up material to Phys. Rev. Lett. 104, 063001 (2010

The laser cooling and trapping of ultracold neutral dysprosium has been demonstrated recently using the broad, open, 421-nm cycling transition. Narrow-line magneto-optical trapping of Dy on longer wavelength transitions would enable the preparation of ultracold Dy samples suitable for loading optical dipole traps and subsequent evaporative cooling. We have identified the closed 741-nm cycling transition as a candidate for the narrow-line cooling of Dy. We present experimental data on the isotope shifts, the hyperfine constants A and B, and the decay rate of the 741-nm transition. In addition, we report a measurement of the 421-nm transition's linewidth, which agrees with previous measurements. We summarize the laser-cooling characteristics of these transitions as well as other narrow cycling transitions that may prove useful for cooling Dy.

Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit populationwide sub-Doppler cooling due to their near degeneracy of excited-and ground-state Landé g factors. We discuss here an additional, unusual intra-MOT sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser intensity and magnetic quadrupole gradient increase beyond critical values. Specifically, anisotropically sub-Dopplercooled cores appear, and their orientation with respect to the quadrupole axis flips at a critical ratio of the MOT laser intensity along the quadrupole axis versus that in the plane of symmetry. This phenomenon can be traced to a loss of the velocity-selective resonance at zero velocity in the cooling force along directions in which the atomic polarization is oriented by the quadrupole field. We present data characterizing this anisotropic laser cooling phenomenon and discuss a qualitative model for its origin based on the extraordinarily large Dy magnetic moment and Dy's near degenerate g factors.