arXiv:cond-mat/9908102 · Physical Review A

Sub-Doppler laser cooling of fermionic 40K atoms

Giovanni Carlo Modugno, Craig Benko, Peter Hannaford, G. Roati, M. Inguscio

Published Nov 1, 1999• 32 citations

Abstract

We report laser cooling of fermionic ${}^{40}\mathrm{K}$ atoms, with temperatures down to $(15\ifmmode\pm\else\textpm\fi{}5) \ensuremath{\mu}\mathrm{K},$ for an enriched sample trapped in a magneto-optical trap and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of 2 of the lowest realizable rms velocity $(\ensuremath{\sim}{3.5v}_{\mathrm{rec}})$ in three-dimensional optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of ${}^{40}\mathrm{K}$ atoms.

DOI: 10.1103/physreva.60.r3373

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arXiv:cond-mat/9908102 · Physical Review A

Sub-Doppler laser cooling of fermionic 40K atoms

Giovanni Carlo Modugno, Craig Benko, Peter Hannaford, G. Roati, M. Inguscio

Published Nov 1, 1999• 32 citations

arXiv HTML PDF

Abstract

We report laser cooling of fermionic

{}^{40}\mathrm{K}

atoms, with temperatures down to

(15\ifmmode\pm\else\textpm\fi{}5) \ensuremath{\mu}\mathrm{K},

for an enriched sample trapped in a magneto-optical trap and additionaly cooled in optical molasses. This temperature is a factor of 10 below the Doppler-cooling limit and corresponds to an rms velocity within a factor of 2 of the lowest realizable rms velocity

(\ensuremath{\sim}{3.5v}_{\mathrm{rec}})

in three-dimensional optical molasses. Realization of such low atom temperatures, up to now only accessible with evaporative cooling techniques, is an important precursor to producing a degenerate Fermi gas of

{}^{40}\mathrm{K}

atoms.

DOI: 10.1103/physreva.60.r3373

Related papers

Sub-Doppler laser cooling and magnetic trapping of natural-abundance fermionic potassium

Mateusz Bocheński, Mariusz Semczuk

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D. Sukachev, A. Sokolov, K. Chebakov +3 more

Sub-Doppler laser cooling in a magneto-optical trap for thulium atoms at a wavelength of 410.6 nm has been experimentally studied. Without any dedicated molasses period of sub-Doppler cooling, the cloud of 3 × 106 atoms at a temperature of 25(5) μK was observed. The measured temperature is significantly lower than the Doppler limit of 240 μK for the cooling transition at 410.6 nm. The high efficiency of the sub-Doppler cooling process is due to a near-degeneracy of the Landé g-factors of the lower 4f 136s 2 (J = 7/2) and the upper 4f 125d 3/26s 2 (J = 9/2) cooling levels.Sub-Doppler laser cooling in a magneto-optical trap for thulium atoms at a wavelength of 410.6 nm has been experimentally studied. Without any dedicated molasses period of sub-Doppler cooling, the cloud of 3 × 106 atoms at a temperature of 25(5) μK was observed. The measured temperature is significantly lower than the Doppler limit of 240 μK for the cooling transition at 410.6 nm. The high efficiency of the sub-Doppler cooling process is due to a near-degeneracy of the Landé g-factors of the lower 4f 136s 2 (J = 7/2) and the upper 4f 125d 3/26s 2 (J = 9/2) cooling levels.

arXiv:1012.5433Journal of Experimental and Theoretical Physics LettersNov 1, 201023 citations

We report laser cooling of fermionic

{}^{40}\mathrm{K}

atoms, with temperatures down to

(15\ifmmode\pm\else\textpm\fi{}5) \ensuremath{\mu}\mathrm{K},

(\ensuremath{\sim}{3.5v}_{\mathrm{rec}})

{}^{40}\mathrm{K}

atoms.

We report on the realization of sub-Doppler laser cooling of sodium atoms in gray molasses using the

{D}_{1}

optical transition $(3s\phantom{\rule{0.16em}{0ex}}^{2}S_{1/2}\ensuremath{\rightarrow}3p\phantom{\rule{0.16em}{0ex}}^{2}P_{1/2})$ at 589.8 nm. The technique is applied to samples containing $3\ifmmode\times\else\texttimes\fi{}{10}^{9}$ atoms, previously cooled to $350\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{K}$ in a magneto-optical trap, and it leads to temperatures as low as $9\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{K}$ and phase-space densities in the range of ${10}^{\ensuremath{-}4}$. The capture efficiency of the gray molasses is larger than 2/3, and we observe no density-dependent heating for densities up to ${10}^{11}\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$.

Sub-Doppler laser cooling of40K with Raman gray molasses on the

{D}_{2}

line

We report on simultaneous sub-Doppler laser cooling of fermionic

^{6}\mathrm{Li}

and

^{40}\mathrm{K}

using the

{D}_{1}

optical transitions. We compare experimental results to a numerical simulation of the cooling process applying a semiclassical Monte Carlo wave-function method. The simulation takes into account the three-dimensional optical molasses setup and the dipole interaction between atoms and the bichromatic light field driving the

{D}_{1}

transitions. We discuss the physical mechanisms at play, identify the important role of coherences between the ground-state hyperfine levels, and compare

{D}_{1}

and

{D}_{2}

sub-Doppler cooling. In 5 ms, the

{D}_{1}

molasses phase greatly reduces the temperature for both

^{6}\mathrm{Li}

and

^{40}\mathrm{K}

at the same time, with final temperatures of 44 and $11\ensuremath{\mu}\mathrm{K}$, respectively. For both species this leads to a phase-space density close to ${10}^{\ensuremath{-}4}$. These conditions are well suited to direct loading of an optical or magnetic trap for efficient evaporative cooling to quantum degeneracy.