Stability of quantum degenerate Fermi gases of tilted polar molecules

Veljić, Vladimir; Pelster, Axel; Balaž, Antun

doi:10.1103/physrevresearch.1.012009

Cited by 8 publications

(9 citation statements)

References 67 publications

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“…This is three times higher than what was reached in degenerate Fermi gases of magnetic atoms [42]. In the near future, intriguing dipolar many-body phenomena such as modifications of collective excitation modes [43], distortion [42] or the collapse [44] of the Fermi sea should be observable in suitable trap geometries and with improved detection of the cloud expansion.…”

Section: Discussionmentioning

confidence: 79%

Evaporation of microwave-shielded polar molecules to quantum degeneracy

Schindewolf,

Bause,

Chen

et al. 2022

Preprint

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Ultracold polar molecules offer strong electric dipole moments and rich internal structure, which makes them ideal building blocks to explore exotic quantum matter [1-8], implement novel quantum information schemes [9][10][11], or test fundamental symmetries of nature [12]. Realizing their full potential requires cooling interacting molecular gases deeply into the quantum degenerate regime. However, the complexity of molecules which makes their collisions intrinsically unstable at the short range, even for nonreactive molecules [13][14][15][16][17][18], has so far prevented the cooling to quantum degeneracy in three dimensions. Here, we demonstrate evaporative cooling of a three-dimensional gas of fermionic sodium-potassium molecules to well below the Fermi temperature using microwave shielding. The molecules are protected from reaching short range with a repulsive barrier engineered by coupling rotational states with a blue-detuned circularly polarized microwave. The microwave dressing induces strong tunable dipolar interactions between the molecules, leading to high elastic collision rates that can exceed the inelastic ones by at least a factor of 460. This large elastic-toinelastic collision ratio allows us to cool the molecular gas down to 21 nanokelvin, corresponding to 0.36 times the Fermi temperature. Such unprecedentedly cold and dense samples of polar molecules open the path to the exploration of novel many-body phenomena, such as the long-sought topological p-wave superfluid states of ultracold matter.

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Section: Discussionmentioning

confidence: 79%

Evaporation of microwave-shielded polar molecules to quantum degeneracy

Schindewolf,

Bause,

Chen

et al. 2022

Preprint

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“…In the opposite case of a relatively small-radius confinement potential, the hydrodynamic approach used in Reference [20] can effectively determine spectra of discrete low-lying modes. Another promising development of the present study is related to the collective modes in ultra-cold Fermi gases with dipolar interactions intensely investigated recently [30][31][32]. Different interaction potentials, as well as a deformation of the Fermi surface [32] can be straightforwardly incorporated in the GPF approach.…”

Section: Discussionmentioning

confidence: 99%

“…Another promising development of the present study is related to the collective modes in ultra-cold Fermi gases with dipolar interactions intensely investigated recently [30][31][32]. Different interaction potentials, as well as a deformation of the Fermi surface [32] can be straightforwardly incorporated in the GPF approach. Finally, we note that the path-integral technique used here has as a specific advantage over some other methods that it explicitly allows the studying of damped collective modes at non-zero temperatures, relevant to the experiments.…”

Section: Discussionmentioning

confidence: 99%

Dispersion and Damping of Phononic Excitations in Fermi Superfluid Gases in 2D

2020

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We calculate the sound velocity and the damping rate of the collective excitations of a 2D fermionic superfluid in a non-perturbative manner. Specifically, we focus on the Anderson–Bogoliubov excitations in the BEC-BCS crossover regime, as these modes have a sound-like dispersion at low momenta. The calculation is performed within the path-integral formalism and the Gaussian pair fluctuation approximation. From the action functional, we obtain the propagator of the collective excitations and determine their dispersion relation by locating the poles of this propagator. We find that there is only one kind of collective excitation, which is stable at T = 0 and has a sound velocity of v F / 2 for all binding energies, i.e., throughout the BEC-BCS crossover. As the temperature is raised, the sound velocity decreases and the damping rate shows a non-monotonous behavior: after an initial increase, close to the critical temperature T C the damping rate decreases again. In general, higher binding energies provide higher damping rates. Finally, we calculate the response functions and propose that they can be used as another way to determine the sound velocity.

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“…Ref. [47,48,55] more recently investigated the effect of the dipolar anisotropy on the time-of-flight expansion and on the angular dependence of the Fermi surface deformation of the ground state in relation to the trap anisotropy, and found that the Fermi surface deforms maximally when the dipoles are tilted along the less confined trap direction. Here, we analyze the interplay of this effect with the otherwise predominant shell structure in the weakly interacting regime.…”

Section: Introductionmentioning

confidence: 99%

Interplay between shell structure and trap deformation in dipolar fermi gases

Bengtsson,

Eriksson,

Josefi

et al. 2020

Preprint

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Finite fermion systems are known to exhibit shell structure in the weakly-interacting regime, as well known from atoms, nuclei, metallic clusters or even quantum dots in two dimensions. All these systems have in common that the particle interactions between electrons or nucleons are spatially isotropic. Dipolar quantum systems as they have been realized with ultra-cold gases, however, are governed by an intrinsic anisotropy of the two-body interaction that depends on the orientation of the dipoles relative to each other. Here we investigate how this interaction anisotropy modifies the shell structure in a weakly interacting two-dimensional anisotropic harmonic trap. Going beyond Hartree-Fock by applying the so-called "importance-truncated" configuration interaction (CI) method as well as quadratic CI with single-and double-substitutions, we show how the magnetostriction in the system may be counteracted upon by a deformation of the isotropic confinement, restoring the symmetry.

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Stability of quantum degenerate Fermi gases of tilted polar molecules

Cited by 8 publications

References 67 publications

Evaporation of microwave-shielded polar molecules to quantum degeneracy

Evaporation of microwave-shielded polar molecules to quantum degeneracy

Dispersion and Damping of Phononic Excitations in Fermi Superfluid Gases in 2D

Interplay between shell structure and trap deformation in dipolar fermi gases

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