Visualization of Dimensional Effects in Collective Excitations of Optically Trapped Quasi-Two-Dimensional Bose Gases

In this Letter, we show that the classical SO(2,1) symmetry of a harmonically trapped Fermi gas in two dimensions is broken by quantum effects. The anomalous correction to the symmetry algebra is given by a two-body operator that is well known as the contact. Taking into account this modification, we are able to derive the virial theorem for the system and a universal relation for the pressure of a homogeneous gas. The existence of an undamped breathing mode is associated with the classical symmetry. We provide an estimate for the anomalous frequency shift of this oscillation at zero temperature and compare the result with a recent experiment by [E. Vogt et al., Phys. Rev. Lett. 108, 070404 (2012)]. Discrepancies are attributed to finite temperature effects.

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“…The effect of a quantum anomaly on a Bose gas at zero temperature has been studied previously in Refs. [20,21].…”

mentioning

confidence: 99%

Quantum Anomaly, Universal Relations, and Breathing Mode of a Two-Dimensional Fermi Gas

Hofmann

2012

Phys. Rev. Lett.

109

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“…, and µ/8E R → µ. Finally, we arrive at an effective 1D Hamiltonian describing our model system [54][55][56][57],…”

Section: A Effective Modelmentioning

confidence: 99%

Unusual behavior of sound velocity of a Bose gas in an optical superlattice at quasi-one-dimension

Chen

et al. 2014

Eur. Phys. J. D

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A Bose gas trapped in a one-dimensional optical superlattice has emerged as a novel superfluid characterized by tunable lattice topologies and tailored band structures. In this work, we focus on the propagation of sound in such a novel system and have found new features on sound velocity, which arises from the interplay between the two lattices with different periodicity and is not present in the case of a condensate in a monochromatic optical lattice. Particularly, this is the first time that the sound velocity is found to first increase and then decrease as the superlattice strength increases even at one dimension. Such unusual behavior can be analytically understood in terms of the competition between the decreasing compressibility and the increasing effective mass due to the increasing superlattice strength. This result suggests a new route to engineer the sound velocity by manipulating the superlattice's parameters. All the calculations based on the mean-field theory are justified by checking the exponent γ of the off-diagonal one-body density matrix that is much smaller than 1. Finally, the conditions for possible experimental realization of our scenario are also discussed.

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“…1, which consists of a BEC with 1D SOC that is trapped in a strongly anisotropic lattice potential. The transverse lattice confinement in the y-and z-directions is sufficiently strong to freeze the atomic motion in these directions, allowing the atomic tunneling only in the xdirection [28]. This realizes an optically trapped quasi-1D BEC with 1D SOC in the x-direction, which can be well described by the GPE [9,[23][24][25][26],…”

Section: Emerging Flat Bands In a Spin-orbit-coupled Becmentioning

confidence: 99%

Probing the flat band of optically trapped spin-orbital-coupled Bose gases using Bragg spectroscopy

Chen

et al. 2015

Phys. Rev. A

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Motivated by the recent efforts in creating flat bands in ultracold atomic systems, we investigate how to probe a flat band in an optically trapped spin-orbital-coupled Bose-Einstein condensate using Bragg spectroscopy. We find that the excitation spectrum and the dynamic structure factor of the condensate are dramatically altered when the band structure exhibits various levels of flatness. In particular, when the band exhibits perfect flatness around the band minima corresponding to a nearinfinite effective mass, a quadratic dispersion emerges in the low-energy excitation spectrum; in sharp contrast, for the opposite case when an ordinary band is present, the familiar linear dispersion arises. Such linear-to-quadratic crossover in the low-energy spectrum presents a striking manifestation of the transition of an ordinary band into a flat band, thereby allowing a direct probe of the flat band by using Bragg spectroscopy.

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Visualization of Dimensional Effects in Collective Excitations of Optically Trapped Quasi-Two-Dimensional Bose Gases

Cited by 17 publications

References 39 publications

Quantum Anomaly, Universal Relations, and Breathing Mode of a Two-Dimensional Fermi Gas

Quantum Anomaly, Universal Relations, and Breathing Mode of a Two-Dimensional Fermi Gas

Unusual behavior of sound velocity of a Bose gas in an optical superlattice at quasi-one-dimension

Probing the flat band of optically trapped spin-orbital-coupled Bose gases using Bragg spectroscopy

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