Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1410.8545 · Physical Review A

Simultaneous sub-Doppler laser cooling of fermionic Li6 and K40 on the D1 line: Theory and experiment

Franz Sievers, Norman Kretzschmar, Diogo Fernandes, Daniel Suchet, Michael Rabinovic, Saijun Wu, Colin Parker, Lev Khaykovich, Christophe Salomon, Frédéric Chevy

Published Feb 23, 2015• 54 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1103/physreva.91.023426

Related papers

Simultaneous sub-Doppler laser cooling of Li6 and Li7 isotopes

Gentle Dash, Tim de Jongh, Maxime Dixmerias +2 more

We report on the simultaneous sub-Doppler laser cooling of $^{6}\mathrm{Li}$ and $^{7}\mathrm{Li}$ isotopes using gray molasses operating on their respective ${D}_{1}$ atomic transitions. For $^{7}\mathrm{Li}$ we show that the sub-Doppler cooling can be achieved with two distinct $\mathrm{\ensuremath{\Lambda}}$-type transitions, where the upper level can be either of the two ${2}^{2}\phantom{\rule{0.16em}{0ex}}{P}_{1/2}$ hyperfine states. We obtain temperatures of $\ensuremath{\sim}85\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{K}$, with atom numbers of $\ensuremath{\sim}{10}^{8}$, and phase-space densities in the range of ${10}^{\ensuremath{-}6}\ensuremath{-}{10}^{\ensuremath{-}5}$ for both isotopes. These conditions provide a good starting point for loading the mixture into an optical dipole trap and performing evaporative cooling to quantum degeneracy. Our work provides a valuable simplification for the preparation of ultracold $^{6}\mathrm{Li}\ensuremath{-}^{7}\mathrm{Li}$ mixtures, which were proven to be a successful system for the study of impurity physics and Bose-Fermi superfluids.

Physical Review A•Sep 12, 2022•2 citations

\Lambda-enhanced Sub-Doppler Cooling of Lithium Atoms in D1 Gray Molasses

Andrew T. Grier, Igor Ferrier-Barbut, Benno S. Rem +4 more

Following the bichromatic sub-Doppler cooling scheme on the D1-line of 40K recently demonstrated in (Fernandes et al. 2012), we introduce a similar technique for 7Li atoms and obtain temperatures of 60 uK while capturing all of the 5x10^8 atoms present from the previous stage. We investigate the influence of the detuning between the the two cooling frequencies and observe a threefold decrease of the temperature when the Raman condition is fulfilled. We interpret this effect as arising from extra cooling due to long-lived coherences between hyperfine states. Solving the optical Bloch equations for a simplified, \Lambda-type three-level system we identify the presence of an efficient cooling force near the Raman condition. After transfer into a quadrupole magnetic trap, we measure a phase space density of ~10^-5. This laser cooling offers a promising route for fast evaporation of lithium atoms to quantum degeneracy in optical or magnetic traps.

•Apr 25, 2013•0 citations

Λ -enhanced sub-Doppler cooling of lithium atoms in D 1 gray molasses

Andrew T. Grier, Igor Ferrier-Barbut, Benno S. Rem +4 more

Following the bichromatic sub-Doppler cooling scheme on the ${D}_{1}$ line of ${}^{40}$K recently demonstrated in Fernandes et al. [Europhys. Lett. 100, 63001 (2012)], we introduce a similar technique for ${}^{7}$Li atoms and obtain temperatures of $60\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{K}$ while capturing all of the $5\ifmmode\times\else\texttimes\fi{}{10}^{8}$ atoms present from the previous stage. We investigate the influence of the detuning between the the two cooling frequencies and observe a threefold decrease of the temperature when the Raman condition is fulfilled. We interpret this effect as arising from extra cooling due to long-lived coherences between hyperfine states. Solving the optical Bloch equations for a simplified $\ensuremath{\Lambda}$-type three-level system we identify the presence of an efficient cooling force near the Raman condition. After transfer into a quadrupole magnetic trap, we measure a phase space density of $\ensuremath{\sim}$${10}^{\ensuremath{-}5}$. This laser cooling offers a promising route for fast evaporation of lithium atoms to quantum degeneracy in optical or magnetic traps.

arXiv:1304.6971•Physical Review A•Jun 12, 2013•132 citations

Sub-Doppler laser cooling of fermionic 40 K atoms in three-dimensional gray optical molasses

Diogo Fernandes, F. Sievers, N. Kretzschmar +3 more

We demonstrate sub-Doppler cooling of 40 K on the D 1 atomic transition. Using a gray-molasses scheme, we efficiently cool a compressed cloud of 6.5 × 10 8 atoms from ∼4 mK to 20 μ K in 8 ms. After transfer to a quadrupole magnetic trap, we measure a phase space density of ∼10 −5 . This technique offers a promising route for fast evaporation of fermionic 40 K.

arXiv:1210.1310•Europhysics Letters (EPL)•Dec 1, 2012•108 citations

Sub-Doppler laser cooling of40K with Raman gray molasses on the ${D}_{2}$ line

G D Bruce, E Haller, Bruno Peaudecerf +6 more

Gray molasses is a powerful tool for sub-Doppler laser cooling of atoms to low temperatures. For alkaline atoms, this technique is commonly implemented with cooling lasers which are blue-detuned from either the D 1 or D 2 line. Here we show that efficient gray molasses can be implemented on the D 2 line of 40 K with red -detuned lasers. We obtained temperatures of , which enables direct loading of atoms from a magneto-optical trap into an optical dipole trap. We support our findings by a one-dimensional model and three-dimensional numerical simulations of the optical Bloch equations which qualitatively reproduce the experimentally observed cooling effects.

arXiv:1612.04583•Journal of Physics B Atomic Molecular and Optical Physics•Apr 12, 2017•24 citations

Simultaneous sub-Doppler laser cooling and optical trapping of bosonic $^{39}$K-$^{133}$Cs and $^{41}$K-$^{133}$Cs mixtures

Mateusz Bocheński, Jakub Dobosz, Koray Dinçer +2 more

We report simultaneous sub-Doppler cooling and optical dipole trapping of $^{39}$K-Cs and $^{41}$K-Cs mixtures. Both mixtures are cooled to temperatures $\sim10$ $\mathrmμ$K, achieving performance comparable to that obtained with each species individually. To the best of our knowledge, this constitutes the first realization of a laser-cooled and optically trapped $^{41}$K-Cs mixture. For the $^{39}$K-Cs mixture, we additionally implement parallel spin-resolved Feshbach spectroscopy enabled by Stern-Gerlach separation. For potassium isotopes, we implement sub-Doppler cooling with $D_1$-line gray molasses, while for cesium the entire cooling sequence is implemented using $D_2$ transitions. We spin-polarize the atoms and confine Bose-Bose mixtures in a 1064 nm optical dipole trap. Using the resulting $^{39}$K-Cs samples, we observe 14 heteronuclear Feshbach loss features. Five agree with resonances reported previously, while nine have, to the best of our knowledge, not been observed experimentally before, including $p$-wave features and resonances in additional spin channels. The shorter lifetime of the $^{41}$K-Cs mixture in the optical dipole trap currently hinders systematic Feshbach spectroscopy, which we therefore do not pursue in this work. To characterize this limitation quantitatively, we study the decay dynamics of $^{39}$K-Cs and $^{41}$K-Cs mixtures under comparable temperature and density conditions, revealing a substantially stronger nonexponential loss in the $^{41}$K-Cs mixture. The demonstrated preparation of ultracold $^{41}$K-Cs mixtures provides a starting point for Feshbach-resonance and photoassociation spectroscopy of this previously unexplored isotopologue. Such measurements are essential for identifying suitable pathways for magnetoassociation and coherent optical transfer, and ultimately for the production of ultracold ground-state $^{41}$KCs molecules.

arXiv:2609.09003•Sep 8, 2026•0 citations
We report on simultaneous sub-Doppler laser cooling of fermionic 6Li^{6}\mathrm{Li}6Li and 40K^{40}\mathrm{K}40K using the D1{D}_{1}D1​ 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 D1{D}_{1}D1​ transitions. We discuss the physical mechanisms at play, identify the important role of coherences between the ground-state hyperfine levels, and compare D1{D}_{1}D1​ and D2{D}_{2}D2​ sub-Doppler cooling. In 5 ms, the D1{D}_{1}D1​ molasses phase greatly reduces the temperature for both 6Li^{6}\mathrm{Li}6Li and 40K^{40}\mathrm{K}40K at the same time, with final temperatures of 44 and 11\ensuremathμK11\ensuremath{\mu}\mathrm{K}11\ensuremathμK, respectively. For both species this leads to a phase-space density close to 10\ensuremath−4{10}^{\ensuremath{-}4}10\ensuremath−4. These conditions are well suited to direct loading of an optical or magnetic trap for efficient evaporative cooling to quantum degeneracy.
We report on the simultaneous sub-Doppler laser cooling of 6Li^{6}\mathrm{Li}6Li and 7Li^{7}\mathrm{Li}7Li isotopes using gray molasses operating on their respective D1{D}_{1}D1​ atomic transitions. For 7Li^{7}\mathrm{Li}7Li we show that the sub-Doppler cooling can be achieved with two distinct $\mathrm{\ensuremath{\Lambda}}$-type transitions, where the upper level can be either of the two 22P1/2{2}^{2}\phantom{\rule{0.16em}{0ex}}{P}_{1/2}22P1/2​ hyperfine states. We obtain temperatures of $\ensuremath{\sim}85\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{K}$, with atom numbers of $\ensuremath{\sim}{10}^{8}$, and phase-space densities in the range of ${10}^{\ensuremath{-}6}\ensuremath{-}{10}^{\ensuremath{-}5}$ for both isotopes. These conditions provide a good starting point for loading the mixture into an optical dipole trap and performing evaporative cooling to quantum degeneracy. Our work provides a valuable simplification for the preparation of ultracold $^{6}\mathrm{Li}\ensuremath{-}^{7}\mathrm{Li}$ mixtures, which were proven to be a successful system for the study of impurity physics and Bose-Fermi superfluids.
Following the bichromatic sub-Doppler cooling scheme on the D1-line of 40K recently demonstrated in (Fernandes et al. 2012), we introduce a similar technique for 7Li atoms and obtain temperatures of 60 uK while capturing all of the 5x10^8 atoms present from the previous stage. We investigate the influence of the detuning between the the two cooling frequencies and observe a threefold decrease of the temperature when the Raman condition is fulfilled. We interpret this effect as arising from extra cooling due to long-lived coherences between hyperfine states. Solving the optical Bloch equations for a simplified, \Lambda-type three-level system we identify the presence of an efficient cooling force near the Raman condition. After transfer into a quadrupole magnetic trap, we measure a phase space density of ~10^-5. This laser cooling offers a promising route for fast evaporation of lithium atoms to quantum degeneracy in optical or magnetic traps.
Following the bichromatic sub-Doppler cooling scheme on the D1{D}_{1}D1​ line of 40{}^{40}40K recently demonstrated in Fernandes et al. [Europhys. Lett. 100, 63001 (2012)], we introduce a similar technique for 7{}^{7}7Li atoms and obtain temperatures of $60\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{K}$ while capturing all of the $5\ifmmode\times\else\texttimes\fi{}{10}^{8}$ atoms present from the previous stage. We investigate the influence of the detuning between the the two cooling frequencies and observe a threefold decrease of the temperature when the Raman condition is fulfilled. We interpret this effect as arising from extra cooling due to long-lived coherences between hyperfine states. Solving the optical Bloch equations for a simplified $\ensuremath{\Lambda}$-type three-level system we identify the presence of an efficient cooling force near the Raman condition. After transfer into a quadrupole magnetic trap, we measure a phase space density of $\ensuremath{\sim}$${10}^{\ensuremath{-}5}$. This laser cooling offers a promising route for fast evaporation of lithium atoms to quantum degeneracy in optical or magnetic traps.
Sub-Doppler laser cooling of40K with Raman gray molasses on the D2{D}_{2}D2​ line
Gray molasses is a powerful tool for sub-Doppler laser cooling of atoms to low temperatures. For alkaline atoms, this technique is commonly implemented with cooling lasers which are blue-detuned from either the D 1 or D 2 line. Here we show that efficient gray molasses can be implemented on the D 2 line of 40 K with red -detuned lasers. We obtained temperatures of , which enables direct loading of atoms from a magneto-optical trap into an optical dipole trap. We support our findings by a one-dimensional model and three-dimensional numerical simulations of the optical Bloch equations which qualitatively reproduce the experimentally observed cooling effects.
Simultaneous sub-Doppler laser cooling and optical trapping of bosonic 39^{39}39K-133^{133}133Cs and 41^{41}41K-133^{133}133Cs mixtures
We report simultaneous sub-Doppler cooling and optical dipole trapping of 39^{39}39K-Cs and 41^{41}41K-Cs mixtures. Both mixtures are cooled to temperatures ∼10\sim10∼10 μ\mathrmμμK, achieving performance comparable to that obtained with each species individually. To the best of our knowledge, this constitutes the first realization of a laser-cooled and optically trapped 41^{41}41K-Cs mixture. For the 39^{39}39K-Cs mixture, we additionally implement parallel spin-resolved Feshbach spectroscopy enabled by Stern-Gerlach separation. For potassium isotopes, we implement sub-Doppler cooling with D1D_1D1​-line gray molasses, while for cesium the entire cooling sequence is implemented using D2D_2D2​ transitions. We spin-polarize the atoms and confine Bose-Bose mixtures in a 1064 nm optical dipole trap. Using the resulting 39^{39}39K-Cs samples, we observe 14 heteronuclear Feshbach loss features. Five agree with resonances reported previously, while nine have, to the best of our knowledge, not been observed experimentally before, including ppp-wave features and resonances in additional spin channels. The shorter lifetime of the 41^{41}41K-Cs mixture in the optical dipole trap currently hinders systematic Feshbach spectroscopy, which we therefore do not pursue in this work. To characterize this limitation quantitatively, we study the decay dynamics of 39^{39}39K-Cs and 41^{41}41K-Cs mixtures under comparable temperature and density conditions, revealing a substantially stronger nonexponential loss in the 41^{41}41K-Cs mixture. The demonstrated preparation of ultracold 41^{41}41K-Cs mixtures provides a starting point for Feshbach-resonance and photoassociation spectroscopy of this previously unexplored isotopologue. Such measurements are essential for identifying suitable pathways for magnetoassociation and coherent optical transfer, and ultimately for the production of ultracold ground-state 41^{41}41KCs molecules.