Seo Ho Youn
University of Illinois at Urbana–Champaign
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Featured researches published by Seo Ho Youn.
Physical Review Letters | 2011
Mingwu Lu; Nathaniel Q. Burdick; Seo Ho Youn; Benjamin Lev
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 spin-polarized narrowline 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 a high-magnetic field.
Physical Review Letters | 2010
Mingwu Lu; Seo Ho Youn; Benjamin Lev
Ultracold dysprosium gases, with a magnetic moment 10 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 microK-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 microK sub-Doppler cooled atoms.
Physical Review A | 2011
Mingwu Lu; Seo Ho Youn; Benjamin Lev
The laser cooling and trapping of ultracold neutral dysprosium has been recently demonstrated 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 transitions 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.
Physical Review A | 2010
Seo Ho Youn; Mingwu Lu; Benjamin Lev
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 Land´ e 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.
Physical Review A | 2010
Seo Ho Youn; Mingwu Lu; Ushnish Ray; Benjamin Lev
Archive | 2011
Seo Ho Youn
Bulletin of the American Physical Society | 2011
Mingwu Lu; Seo Ho Youn; Richard Turner; Matthew Naides; Nathaniel Q. Burdick; Alicia Kollar; Nobie Redmon; Benjamin Lev
Archive | 2010
Seo Ho Youn; Mingwu Lu; Benjamin Lev
Frontiers in Optics | 2010
Benjamin Lev; Mingwu Lu; Seo Ho Youn
Bulletin of the American Physical Society | 2009
Seo Ho Youn; Mingwu Lu; Ushnish Ray; Benjamin Lev