arXiv:1110.4552 · Physical Review A

Quantum degenerate Bose-Fermi mixture of chemically different atomic species with widely tunable interactions

Jee Woo Park, Cheng-Hsun Wu, Ibon Santiago, Tobias Tiecke, Sebastian Will, Peyman Ahmadi, Martin W. Zwierlein

Published May 9, 2012• 131 citations

Abstract

We have created a quantum degenerate Bose-Fermi mixture of ${}^{23}$Na and ${}^{40}$K with widely tunable interactions via broad interspecies Feshbach resonances. Over 30 Feshbach resonances between ${}^{23}$Na and ${}^{40}$K were identified, including $p$-wave multiplet resonances. The large and negative triplet background scattering length between ${}^{23}$Na and ${}^{40}$K causes a sharp enhancement of the fermion density in the presence of a Bose condensate. As explained via the asymptotic bound-state model, this strong background scattering leads to wide Feshbach resonances observed at low magnetic fields. Our work opens up the prospect to create chemically stable, fermionic ground-state molecules of ${}^{23}$Na-${}^{40}$K, where strong, long-range dipolar interactions would set the dominant energy scale.

DOI: 10.1103/physreva.85.051602

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arXiv:1110.4552 · Physical Review A

Quantum degenerate Bose-Fermi mixture of chemically different atomic species with widely tunable interactions

Jee Woo Park, Cheng-Hsun Wu, Ibon Santiago, Tobias Tiecke, Sebastian Will, Peyman Ahmadi, Martin W. Zwierlein

Published May 9, 2012• 131 citations

arXiv HTML PDF

Abstract

We have created a quantum degenerate Bose-Fermi mixture of

{}^{23}

Na and

{}^{40}

K with widely tunable interactions via broad interspecies Feshbach resonances. Over 30 Feshbach resonances between

{}^{23}

Na and

{}^{40}

K were identified, including

p

-wave multiplet resonances. The large and negative triplet background scattering length between

{}^{23}

Na and

{}^{40}

K causes a sharp enhancement of the fermion density in the presence of a Bose condensate. As explained via the asymptotic bound-state model, this strong background scattering leads to wide Feshbach resonances observed at low magnetic fields. Our work opens up the prospect to create chemically stable, fermionic ground-state molecules of

{}^{23}

Na-

{}^{40}

K, where strong, long-range dipolar interactions would set the dominant energy scale.

DOI: 10.1103/physreva.85.051602

Related papers

Dual-species Bose-Einstein condensates of $^{23}$ Na and $^{41}$ K with tunable interactionsDual-species Bose-Einstein condensates of $^{23}$Na and $^{41}$K with tunable interactions

Jaeryeong Chang, Sung‐Jun Lee, Yoonsoo Kim +2 more

We report the creation of dual-species Bose-Einstein condensates (BECs) of $^{23}$ Na and $^{41}$ K. Favorable background scattering lengths enable efficient sympathetic cooling of $^{41}$ K via forced evaporative cooling of $^{23}$ Na in a plugged magnetic trap and an optical dipole trap. The $1/e$ lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about $3\times10^5$ $^{23}$ Na atoms surrounding $5\times10^4$ $^{41}$ K atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest $s$ -wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic $^{23}$ Na $^{41}$ K molecules as well as the exploration of many-body physics in bosonic $^{23}$ Na- $^{41}$ K mixtures.We report the creation of dual-species Bose-Einstein condensates (BECs) of $^{23}$Na and $^{41}$K. Favorable background scattering lengths enable efficient sympathetic cooling of $^{41}$K via forced evaporative cooling of $^{23}$Na in a plugged magnetic trap and an optical dipole trap. The $1/e$ lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about $3\times10^5$ $^{23}$Na atoms surrounding $5\times10^4$ $^{41}$K atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest $s$-wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic $^{23}$Na$^{41}$K molecules as well as the exploration of many-body physics in bosonic $^{23}$Na-$^{41}$K mixtures.

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Broad Feshbach Resonance with a Large Background Scattering Length in a Fermionic Atom-Molecule Mixture

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Formation of bosonic Na 23 K 41 Feshbach molecules

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Ultracold Feshbach molecules are a crucial intermediate step for the creation of quantum degenerate gases of strongly dipolar molecules. After coherent transfer to the rovibrational ground state, these dimers can realize stable dipolar gases with strong, tunable long-range interactions. Here, we report the creation of bosonic Na 23 K 41 Feshbach molecules by radio-frequency (RF) association. An RF pulse applied on the molecular side of an interspecies Feshbach resonance at 73.6(1) G associates up to 1.1 ( 1 ) × 10 4 molecules from a thermal mixture of Na 23 and K 41 atoms. Measurements of the binding energy reveal a broad resonance width of 5.1(2) G, facilitating robust control over interspecies interactions. The molecule lifetime in the presence of background atoms exceeds 2 ms and increases to approximately 7 ms after removal of Na 23 . These results constitute a key step toward the production of ultracold Na 23 K 41 ground-state molecules and for pursuing shielded evaporative cooling in the dipolar regime.Ultracold Feshbach molecules are a crucial intermediate step for the creation of quantum degenerate gases of strongly dipolar molecules. After coherent transfer to the rovibrational ground state, these dimers can realize stable dipolar gases with strong, tunable long-range interactions. Here, we report the creation of bosonic Na 23 K 41 Feshbach molecules by radio-frequency (RF) association. An RF pulse applied on the molecular side of an interspecies Feshbach resonance at 73.6(1) G associates up to 1.1 ( 1 ) × 10 4 molecules from a thermal mixture of Na 23 and K 41 atoms. Measurements of the binding energy reveal a broad resonance width of 5.1(2) G, facilitating robust control over interspecies interactions. The molecule lifetime in the presence of background atoms exceeds 2 ms and increases to approximately 7 ms after removal of Na 23 . These results constitute a key step toward the production of ultracold Na 23 K 41 ground-state molecules and for pursuing shielded evaporative cooling in the dipolar regime.

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We report the creation of dual-species Bose-Einstein condensates (BECs) of Na23 and K41 . Favorable background scattering lengths enable efficient sympathetic cooling of K41 via forced evaporative cooling of Na23 in a plugged magnetic trap and an optical dipole trap. The 1/e lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about 3×105 Na23 atoms surrounding 5×104 K41 atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest s -wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic Na23K41 molecules as well as the exploration of many-body physics in bosonic Na23−K41 mixtures. Published by the American Physical Society 2024We report the creation of dual-species Bose-Einstein condensates (BECs) of Na23 and K41 . Favorable background scattering lengths enable efficient sympathetic cooling of K41 via forced evaporative cooling of Na23 in a plugged magnetic trap and an optical dipole trap. The 1/e lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about 3×105 Na23 atoms surrounding 5×104 K41 atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest s -wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic Na23K41 molecules as well as the exploration of many-body physics in bosonic Na23−K41 mixtures. Published by the American Physical Society 2024

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Strongly interacting isotopic Bose-Fermi mixture immersed in a Fermi sea

Cheng-Hsun Wu, Ibon Santiago, Jee Woo Park +2 more

We have created a triply quantum-degenerate mixture of bosonic $^{41}\mathrm{K}$ and two fermionic species $^{40}\mathrm{K}$ and $^{6}\mathrm{Li}$ . The boson is shown to be an efficient coolant for the two fermions, spurring hopes for the observation of fermionic superfluids with imbalanced masses. We observe multiple heteronuclear Feshbach resonances, in particular a wide $s$ -wave resonance for the combination $^{41}\mathrm{K}$ - $^{40}\mathrm{K}$ , opening up studies of strongly interacting isotopic Bose-Fermi mixtures. For large imbalance in the local densities of different species, we enter the polaronic regime of dressed impurities immersed in a bosonic or fermionic bath.We have created a triply quantum-degenerate mixture of bosonic $^{41}\mathrm{K}$ and two fermionic species $^{40}\mathrm{K}$ and $^{6}\mathrm{Li}$. The boson is shown to be an efficient coolant for the two fermions, spurring hopes for the observation of fermionic superfluids with imbalanced masses. We observe multiple heteronuclear Feshbach resonances, in particular a wide $s$-wave resonance for the combination $^{41}\mathrm{K}$-$^{40}\mathrm{K}$, opening up studies of strongly interacting isotopic Bose-Fermi mixtures. For large imbalance in the local densities of different species, we enter the polaronic regime of dressed impurities immersed in a bosonic or fermionic bath.

arXiv:1103.4630Physical Review AJul 13, 2011113 citations

We have created a quantum degenerate Bose-Fermi mixture of

{}^{23}

Na and

{}^{40}

K with widely tunable interactions via broad interspecies Feshbach resonances. Over 30 Feshbach resonances between

{}^{23}

Na and

{}^{40}

K were identified, including

p

-wave multiplet resonances. The large and negative triplet background scattering length between

{}^{23}

Na and

{}^{40}

{}^{23}

Na-

{}^{40}

K, where strong, long-range dipolar interactions would set the dominant energy scale.

Dual-species Bose-Einstein condensates of

^{23}

Na and

^{41}

K with tunable interactions

We report the creation of dual-species Bose-Einstein condensates (BECs) of

^{23}

Na and

^{41}

K. Favorable background scattering lengths enable efficient sympathetic cooling of

^{41}

K via forced evaporative cooling of

^{23}

Na in a plugged magnetic trap and an optical dipole trap. The

1/e

lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about

3\times10^5

^{23}

Na atoms surrounding

5\times10^4

^{41}

K atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest

s

-wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic

^{23}

^{41}

K molecules as well as the exploration of many-body physics in bosonic

^{23}

Na-

^{41}

K mixtures.

We have successfully prepared an optically trapped ultracold mixture of

{}^{23}

Na and

{}^{87}

Rb atoms and studied their interspecies Feshbach resonances. Using two different spin combinations, several

s

- and

p

-wave resonances are identified by observing high inelastic losses and temperature increases for both species near resonant magnetic field values. The two

s

-wave resonances observed below 500 G between atoms in their lowest-energy levels are possible candidates for Feshbach molecule association. Our results are well characterized by a coupled-channel model which also refines the ground-state interaction potentials between

{}^{23}

Na and

{}^{87}

Rb. This work opens up the prospect for preparing ultracold ensembles of ground-state bosonic NaRb molecules which are chemically stable and can provide strong dipolar interactions.

We have created a triply quantum-degenerate mixture of bosonic

^{41}\mathrm{K}

and two fermionic species

^{40}\mathrm{K}

and

^{6}\mathrm{Li}

. The boson is shown to be an efficient coolant for the two fermions, spurring hopes for the observation of fermionic superfluids with imbalanced masses. We observe multiple heteronuclear Feshbach resonances, in particular a wide

s

-wave resonance for the combination

^{41}\mathrm{K}

^{40}\mathrm{K}

, opening up studies of strongly interacting isotopic Bose-Fermi mixtures. For large imbalance in the local densities of different species, we enter the polaronic regime of dressed impurities immersed in a bosonic or fermionic bath.