Periodically Dressed Bose-Einstein Condensate: A Superfluid with an Anisotropic and Variable Critical Velocity

Higbie, James; Stamper-Kurn, Dan

doi:10.1103/physrevlett.88.090401

Cited by 80 publications

(96 citation statements)

References 15 publications

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“…This is precisely what Lin and colleagues 2 achieved in their ingenious experimental set-up, which is an inspired realization of earlier proposals [3][4][5][6] . Using a pair of laser beams, they first imprinted the equivalent of a river's uniform flow -a uniform vector potential -on their ultracold cloud of atoms 7,8 .…”

supporting

confidence: 71%

Neutral atoms put in charge

Zwierlein¹

2009

Nature

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An elegant experiment shows that atoms subjected to a pair of laser beams can behave like electrons in a magnetic field, as demonstrated by the appearance of quantized vortices in a neutral superfluid.Ultracold gases of atoms -a million times thinner than air and a million times colder than interstellar space -allow the observation and control of many-body quantum physics at macroscopic scales. They can thus serve as model materials 1 for condensed-matter systems where such quantum behaviour dominates. From frictionless flow in superfluids to inhibited transport in insulators and from weakly to strongly interacting systems, an extreme variety of fundamental states of matter can be realized in ultracold atomic gases in real time and with the precision of atomic physics. But there seems to be one obvious limitation: atoms are neutral, a fact that in principle precludes the observation of a wealth of phenomena tied to the behaviour of charged particles, for example their behaviour in a magnetic field. On page 000 of this issue, Lin et al. 2 get round this problem and demonstrate in a striking fashion their ability to create synthetic magnetic fields for a neutral ultracold atomic system -A collective state of matter termed a Bose-Einstein condensate develops mini-tornadoes known as quantized vortices. velocity (blue arrows) does not rotate. b, If the water flows non-uniformly and in a different direction on one side of the paddle wheel from that on the other, the wheel rotates (green arrow). The flow pattern is analogous to the 'vector potential' created in Lin and colleagues' experiment 2 to generate a synthetic magnetic field for an ultracold cloud of atoms known as a Bose-Einstein condensate. The rotation axis (purple arrow) and the speed with which the paddle wheel rotates correspond respectively to the direction and strength of the magnetic field. c, d, Images of the BoseEinstein condensate before (c) and after (d) application of the synthetic magnetic field. The appearance of quantized vortices (d) is a direct demonstration of a synthetic magnetic field.

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supporting

confidence: 71%

Neutral atoms put in charge

Zwierlein¹

2009

Nature

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“…In a biased double well such as the one shown in Fig. 1 a BEC in the ground state occupies only one of the two double well minima [16]. Compared to the single-particle spectrum, the second minimum is modified due to the interaction energy, and for small excitation momenta the collective excitation spectrum becomes linear (phonon modes).…”

mentioning

confidence: 99%

“…Compared to the single-particle spectrum, the second minimum is modified due to the interaction energy, and for small excitation momenta the collective excitation spectrum becomes linear (phonon modes). The resulting dispersion is reminiscent of the phonon-maxon-roton like structure [16][17][18] Moreover, the presence of the nonlinearity leads to several phenomena within the collective excitation spectrum which are absent in the single-particle dispersion. One of the most fundamental of these is the softening of the roton-like modes when the spin-orbit coupling parameters are changed appropriately.…”

mentioning

confidence: 99%

“…Compared to the single-particle spectrum, the second minimum is modified due to the interaction energy, and for small excitation momenta the collective excitation spectrum becomes linear (phonon modes). The resulting dispersion is reminiscent of the phonon-maxon-roton like structure [16][17][18] that appears in the excitation spectrum of many interesting systems, such as liquid 4 He [19], BECs with dipolar interactions [2,3], fractional quantum Hall insulators [20] and antiferromagnets [21].…”

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confidence: 99%

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Measurement of collective excitations in a spin-orbit-coupled Bose-Einstein condensate

et al. 2014

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We measure the collective excitation spectrum of a spin-orbit coupled Bose-Einstein condensate using Bragg spectroscopy. The spin-orbit coupling is generated by Raman dressing of atomic hyperfine states. When the Raman detuning is reduced, mode softening at a finite momentum is revealed, which provides insight towards a supersolid-like phase transition. We find that for the parameters of our system, this softening stops at a finite excitation gap and is symmetric under a sign change of the Raman detuning. Finally, using a moving barrier that is swept through the BEC, we also show the effect of the collective excitation on the fluid dynamics.PACS numbers: 03.75. Kk, 03.75.Mn, 32.80.Qk, 71.70.Ej Since the achievement of Bose-Einstein condensation (BEC) in dilute atomic gases, the investigation of collective excitations has been a key tool to gain insight into this unusual state of matter [1]. For most atomic species used in BEC experiments the interactions between the ultracold atoms can be described by isotropic, short-range s-wave scattering, which leads to the well-known linear phonon excitation spectrum at low momentum. However, if long-range interactions, such as dipolar interactions, are present, the collective excitation spectrum of a BEC can exhibit a more complex structure: in addition to the typical low energy phonon spectrum, a roton-like structure can appear. It is characterised by a shoulder in the spectrum, which for certain parameters can turn into a parabolic minimum at a finite momentum [2][3][4][5].Interestingly, a similar parabolic minimum at a finite momentum can also exist in spin-orbit coupled (SOC) systems. In cold atomic gases, spin-orbit coupling can be implemented by Raman dressing of two or more atomic hyperfine states, which play the role of different (pseudo-)spins. The Raman lasers are arranged in such a way that a Raman transition between the states is accompanied by a change of momentum [6][7][8][9][10][11]. Since the Raman coupling strength and the detuning from the Raman resonance can be independently adjusted in an experiment, this provides a very flexible platform to engineer interesting dispersion relations and test spin-orbit coupled physics (for a review, see, e.g., [12][13][14][15]). In the single-particle picture, the effect of the Raman dressing is to displace two copies of the parabolic dispersion originating from the kinetic energy of the particle in opposite directions in momentum space. The Raman coupling opens a gap at the crossing of these two parabolas so that the resulting single-particle dispersion has the form of a double well in momentum space. The double well can be biased towards either minimum by changing the Raman detuning. When the Raman detuning or the Raman coupling exceed a critical value, one of the minima disappears and a single well dispersion results. * engels@wsu.eduIn the presence of nonlinear effects stemming from the s-wave scattering between the atoms in a Raman dressed BEC, the double well structure continues to exist. In a biased double wel...

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“…More recently, the so-called "synthetic" magnetic field approach is developed [14][15][16], which creates an effective gauge potential A for neutral atoms by means of optical field [17][18][19], instead of rotating the frame. In this case, atoms behave like charged particles in magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic properties of rotating trapped ideal Bose gases

Li¹,

Gu²

2014

Physics Letters A

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Ultracold atomic gases can be spined up either by confining them in rotating frame, or by introducing "synthetic" magnetic field. In this paper, thermodynamics of rotating ideal Bose gases are investigated within truncated-summation approach which keeps to take into account the discrete nature of energy levels, rather than to approximate the summation over single-particle energy levels by an integral as does in semi-classical approximation. Our results show that Bose gases in rotating frame exhibit much stronger dependence on rotation frequency than those in "synthetic" magnetic field. Consequently, BEC can be more easily suppressed in rotating frame than in "synthetic" magnetic field.

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Periodically Dressed Bose-Einstein Condensate: A Superfluid with an Anisotropic and Variable Critical Velocity

Cited by 80 publications

References 15 publications

Neutral atoms put in charge

Neutral atoms put in charge

Measurement of collective excitations in a spin-orbit-coupled Bose-Einstein condensate

Thermodynamic properties of rotating trapped ideal Bose gases

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