Control of dipolar relaxation in external fields

Pasquiou, Benjamin; Bismut, G.; Beaufils, Quentin; Crubellier, A.; Maréchal, É.; Pedri, P.; Vernac, L.; Gorceix, O.; Laburthe‐Tolra, B.

doi:10.1103/physreva.81.042716

Cited by 80 publications

(176 citation statements)

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“…Since the modulation of the magnetic field is parallel to the magnetic bias field, only transitions between states with the same projection quantum number of the total angular momentum are observed. This procedure has been successfully applied in several experiments [37,[53][54][55][56][57][58] to determine atomic scattering properties.…”

Section: Binding Energy Measurementsmentioning

confidence: 99%

Feshbach resonances, weakly bound molecular states, and coupled-channel potentials for cesium at high magnetic fields

et al. 2013

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We explore the scattering properties of ultracold ground-state Cs atoms at magnetic fields between 450 G (45 mT) and 1000 G. We identify 17 previously unreported Feshbach resonances, including two very broad ones near 549 and 787 G. We measure the binding energies of several different dimer states by magnetic field modulation spectroscopy. We use least-squares fitting to these experimental results, together with previous measurements at lower field, to determine a six-parameter model of the long-range interaction potential, designated M2012. Coupled-channels calculations using M2012 provide an accurate mapping between the s-wave scattering length and the magnetic field over the entire range of fields considered. This mapping is crucial for experiments that rely on precise tuning of the scattering length, such as those on Efimov physics.

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Section: Binding Energy Measurementsmentioning

confidence: 99%

Feshbach resonances, weakly bound molecular states, and coupled-channel potentials for cesium at high magnetic fields

et al. 2013

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“…The role Fermi statistics might play in suppressing dipolar relaxation was discussed in Ref. [9], but has never been experimentally investigated.By comparing dipolar relaxation rates in both ultracold bosonic and fermionic dysprosium, we find that spin relaxation is enhanced among bosons while suppressed among fermions. This supports the conclusion that quantum statistics play a substantial role in these collisions: The more energy that is released, the less frequently these exothermic reactions take place, and only quantum spin statistics can explain this counterintuitive effect.…”

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confidence: 99%

“…Inelastic dipolar collisions among highly magnetic atoms in magnetostatic traps were considered in the context of bosonic Cr gases at fifty to hundreds of µK [7] and at a few hundred nK [9] and Dy gases at hundreds of mK [23] and at a few hundred µK [24]. The authors of Ref.…”

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confidence: 99%

“…The long-range, r −3 nature of the dipolar interaction leads to an elastic cross section independent of k i and proportional to the fourth power of the magnetic dipole moment µ regardless of quantum statistics in the limit k i → 0 [7][8][9] [10]. This manifestation of universal dipolar scattering implies that sufficiently strong dipolar interactions allow spin-polarized fermions to evaporatively cool even at energies comparable to and below the Fermi temperature T F .…”

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“…The role Fermi statistics might play in suppressing dipolar relaxation was discussed in Ref. [9], but has never been experimentally investigated.…”

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Fermionic Suppression of Dipolar Relaxation

Burdick¹,

Baumann²,

Tang³

et al. 2015

Phys. Rev. Lett.

119

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We observe the suppression of inelastic dipolar scattering in ultracold Fermi gases of the highly magnetic atom dysprosium: the more energy that is released, the less frequently these exothermic reactions take place, and only quantum spin statistics can explain this counterintuitive effect. Inelastic dipolar scattering in non-zero magnetic fields leads to heating or to loss of the trapped population, both detrimental to experiments intended to study quantum many-body physics with strongly dipolar gases. Fermi statistics, however, is predicted to lead to a kinematic suppression of these harmful reactions. Indeed, we observe a 120-fold suppression of dipolar relaxation in fermionic versus bosonic Dy, as expected from theory describing universal inelastic dipolar scattering, though never before experimentally confirmed. Similarly low inelastic cross sections are observed in spin mixtures, also with striking correspondence to universal dipolar scattering predictions. The suppression of relaxation opens the possibility of employing fermionic dipolar species-atoms or molecules-in studies of quantum many-body physics involving, e.g., synthetic gauge fields and pairing. Spin-statistics play a prominent role in determining the character and rate of elastic collisions among ultracold atoms or molecules [1][2][3], often leading to the enhancement or suppression of thermalization. For example, elastic collisions mediated by short-range interactions between spin-polarized fermions are suppressed at low velocity. The reason lies in the requirement that the total two-particle state-the tensor product of spin and orbital-must be antisymmetric both before and after a collision [4]. Because the orbital wavefunction must be of odd parity for spin-polarized fermions, collisions between two such atoms are inhibited by the p-wave centrifugal energy barrier [5]. For van der Waals interactions, this leads to a kinematic suppression of the elastic cross section as k i → 0, where the wavevector k i is proportional to the relative incoming momentum. The fermionic suppression of thermalizing elastic collisions has an important, well-known consequence: inefficient evaporative cooling near quantum degeneracy [6].This unfavorable scaling is modified in the case of 3D dipolar interactions. The long-range, r −3 nature of the dipolar interaction leads to an elastic cross section independent of k i and proportional to the fourth power of the magnetic dipole moment µ regardless of quantum statistics in the limit k i → 0 [7][8][9][10]. This manifestation of universal dipolar scattering implies that sufficiently strong dipolar interactions allow spin-polarized fermions to evaporatively cool even at energies comparable to and below the Fermi temperature T F . Here "universal" means short-range physics plays no role; scattering only depends on atomic parameters through µ and mass [8] and not on, e.g., the difficult-to-calculate phaseshifts of partial-waves at short range [11]. Indeed, recent experiments employing the highly dipolar fermionic gases KRb...

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Simulating quantum magnets with symmetric top molecules

2013

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We establish a correspondence between the electric dipole matrix elements of a polyatomic symmetric top molecule in a state with nonzero projection of the total angular momentum on the symmetry axis of the molecule and the magnetic dipole matrix elements of a magnetic dipole associated with an elemental spin $F$. It is shown that this correspondence makes it possible to perform quantum simulation of the single-particle spectrum and the dipole-dipole interactions of magnetic dipoles in a static external magnetic field $\bf{B}$ with symmetric top molecules subject to a static external electric field $\bf{E}_{\mathrm{DC}}$. We further show that no such correspondence exists for $^1\Sigma$ molecules in static fields, such as the alkali metal dimers. The effective spin angular momentum of the simulated magnetic dipole corresponds to the rotational angular momentum of the symmetric top molecule, and so quantum simulation of arbitrarily large integer spins is possible. Further, taking the molecule CH$_3$F as an example, we show that the characteristic dipole-dipole interaction energies of the simulated magnetic dipole are a factor of 620, 600, and 310 larger than for the highly magnetic atoms Chromium, Erbium, and Dysprosium, respectively. We present several applications of our correspondence for many-body physics, including long-range and anisotropic spin models with arbitrary integer spin $S$ using symmetric top molecules in optical lattices, quantum simulation of molecular magnets, and spontaneous demagnetization of Bose-Einstein condensates due to dipole-dipole interactions. Our results are expected to be relevant as cold symmetric top molecules reach quantum degeneracy through Stark deceleration and opto-electrical cooling.Comment: 28 pages, 3 figures, submitted to the special issue of Annalen der Physik on "Quantum Simulation"; v2: revised in response to referees' comment

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Control of dipolar relaxation in external fields

Cited by 80 publications

References 69 publications

Feshbach resonances, weakly bound molecular states, and coupled-channel potentials for cesium at high magnetic fields

Feshbach resonances, weakly bound molecular states, and coupled-channel potentials for cesium at high magnetic fields

Fermionic Suppression of Dipolar Relaxation

Simulating quantum magnets with symmetric top molecules

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