Observation of roton mode population in a dipolar quantum gas

Chomaz, Lauriane; Bijnen, Rick van; Petter, D.; Faraoni, Giulia; Baier, Simon; Becher, Jan Hendrik; Mark, Manfred J.; Wächtler, F.; Santos, Luís; Ferlaino, Francesca

doi:10.1038/s41567-018-0054-7

Cited by 264 publications

(317 citation statements)

References 47 publications

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“…A mixture of 39 K in two different spin states has been predicted to be especially suited for these studies [52,53]. Similar droplets have recently been observed in dipolar condensates [55][56][57].…”

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confidence: 49%

Production of strongly bound K39 bright solitons

et al. 2016

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We report on the production of 39 K matter-wave bright solitons, i.e., 1D matter-waves that propagate without dispersion thanks to attractive interactions. The volume of the soliton is studied as a function of the scattering length through three-body losses, revealing peak densities as high as ∼ 5 × 10 20 m −3 . Our solitons, close to the collapse threshold, are strongly bound and will find applications in fundamental physics and atom interferometry.PACS numbers: 03.75. Lm, Solitons are one-dimensional wave-packets that propagate with neither change of shape nor loss of energy. They are a consequence of non-linearities that balance wave-packet spreading due to dispersion. They appear in numerous physical systems such as water waves, optical fibers, plasmas, acoustic waves or even in energy propagation along proteins [1]. Solitons are also observed in ultracold quantum gases [2][3][4][5][6]. In this context, matterwave bright solitons are Bose-Einstein condensates that remain bound thanks to mean-field attractive interactions in a one dimensional geometry [2,3].Matter-wave bright solitons are predicted to be a great tool to locally probe rapidly varying forces for example close to a surface [7,8], or probe (surface) bound states [7,9] which do not appear in linear scattering. For example, the small size of bright solitons has been used in the measurement of quantum reflection from a barrier [10,11]. Because of their dispersion-free propagation, bright solitons are also believed to be good candidates for performing very long time atom interferometry measurements [12] although interactions may cause additional phase shifts [13][14][15][16]. Recently, an experiment demonstrated an increased visibility for a soliton atomic interferometer as compared to its non interacting counterpart [17]. The interactions in solitons can also lead to squeezed or entangled states, which could improve the sensitivity of interferometric measurements beyond the shot noise limit [18][19][20][21][22][23][24]. In some cases, the formation of mesoscopic Schrödinger cat states or NOON states is predicted [25][26][27]. A problem in using these states is losses, such as three-body collisions, which are an intrinsic source of decoherence. They can also induce unusual soliton center of mass dynamics [28].Experiments producing and studying matter-wave bright solitons, despite their interest in both applied and fundamental physics, have remained scarce. In fact, only two elements have been turned into bright solitons, 7 Li [2, 3, 29, 30] and 85 Rb [10,31]. In this paper, we describe the production of 39 K solitons in the |F = 1, m F = −1 state using the Feshbach resonance at 561 G [32] and its associated zero-crossing of the scattering length at 504.4 G (see figure 1). We have optimized the setup in order to produce strongly bound solitons, i.e., solitons with a large negative interaction energy. We thus pro- The evaporation to Bose-Einstein condensation takes place at 550 G (red bullet). The magnetic field is then ramped in two steps to 507 G (vi...

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Production of strongly bound K39 bright solitons

et al. 2016

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“…Here, B m denotes the Bohr magneton. Such species exhibit fascinating phenomena, such as the Rosensweig instability [8], the emergence of quantum-stabilised droplets [9][10][11] and roton quasiparticles [12]. Correspondingly, all these developments triggered much theoretical work, including, but not limited to, the numerical effort to simulate dipolar quantum gases in fully anisotropic traps [13][14][15][16][17], the roton instability in pancake-shaped condensates [18][19][20], the investigation of beyond-mean-field effects in onecomponent [21,22] and two-component [23] gases, the formation of the previously observed droplets [24][25][26], their ground-state properties and elementary excitations [27][28][29], the role of three-body interactions [30], and the self-bounded nature of the droplets [26].…”

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confidence: 99%

Ground state of an ultracold Fermi gas of tilted dipoles in elongated traps

et al. 2018

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Many-body dipolar effects in Fermi gases are quite subtle as they energetically compete with the large kinetic energy at and below the Fermi surface (FS). Recently it was experimentally observed in a sample of erbium atoms that its FS is deformed from a sphere to an ellipsoid due to the presence of the anisotropic and long-range dipole-dipole interaction Aikawa et al (2014 Science 345 1484). Moreover, it was suggested that, when the dipoles are rotated by means of an external field, the FS follows their rotation, thereby keeping the major axis of the momentum-space ellipsoid parallel to the dipoles. Here we generalise a previous Hartree-Fock mean-field theory to systems confined in an elongated triaxial trap with an arbitrary orientation of the dipoles relative to the trap. With this we study for the first time the effects of the dipoles' arbitrary orientation on the ground-state properties of the system. Furthermore, taking into account the geometry of the system, we show how the ellipsoidal FS deformation can be reconstructed, assuming ballistic expansion, from the experimentally measurable real-space aspect ratio after a free expansion. We compare our theoretical results with new experimental data measured with erbium Fermi gas for various trap parameters and dipole orientations. The observed remarkable agreement demonstrates the ability of our model to capture the full angular dependence of the FS deformation. Moreover, for systems with even higher dipole moment, our theory predicts an additional unexpected effect: the FS does not simply follow rigidly the orientation of the dipoles, but softens showing a change in the aspect ratio depending on the dipoles' orientation relative to the trap geometry, as well as on the trap anisotropy itself. Our theory provides the basis for understanding and interpreting phenomena in which the investigated physics depends on the underlying structure of the FS, such as fermionic pairing and superfluidity.

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“…Indeed, in addition to short-range on-site interactions, it is now possible to engineer also long-range interactions using ultracold molecules, Rydberg-dressed atoms, and dipolar atoms [3][4][5][6][7][8]. Trapping dipolar atoms in optical lattices to form itinerant models has recently been achieved experimentally [3].…”

Section: Introductionmentioning

confidence: 99%

Fast trimers in a one-dimensional extended Fermi-Hubbard model

2018

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We consider a one-dimensional two-component extended Fermi-Hubbard model with nearest-neighbor interactions and mass imbalance between the two species. We study the binding energy of trimers, various observables for detecting them, and expansion dynamics. We generalize the definition of the trimer gap to include the formation of different types of clusters originating from nearest-neighbor interactions. Expansion dynamics reveal rapidly propagating trimers, with speeds exceeding doublon propagation in the strongly interacting regime. We present a simple model for understanding this unique feature of the movement of the trimers, and we discuss the potential for experimental realization.

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Observation of roton mode population in a dipolar quantum gas

Cited by 264 publications

References 47 publications

Production of strongly bound K39 bright solitons

Production of strongly bound K39 bright solitons

Ground state of an ultracold Fermi gas of tilted dipoles in elongated traps

Fast trimers in a one-dimensional extended Fermi-Hubbard model

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