We study superfluidity of a cigar-shaped Bose-Einstein condensate by stirring it with a Gaussian potential oscillating back and forth along the axial dimension of the condensate, motivated by experiments of Raman et al. [Phys. Rev. Lett. 83, 2502 (1999)]. Using classical-field simulations and perturbation theory, we examine the induced heating rate, based on the total energy of the system, as a function of the stirring velocity $v$ . We identify the onset of dissipation by a sharply increasing heating rate above a velocity ${v}_{c}$ , which we define as the critical velocity. We show that ${v}_{c}$ is influenced by the oscillating motion, the strength of the stirrer, the temperature, and the inhomogeneous density of the cloud. This results in a vanishing ${v}_{c}$ for the parameters similar to the experiments, which is inconsistent with the measurement of nonzero ${v}_{c}$ . However, if the heating rate is based on the thermal fraction after a $100\phantom{\rule{4pt}{0ex}}\mathrm{ms}$ equilibration time, our simulation recovers the experimental observations. We demonstrate that this discrepancy is due to the slow relaxation of the stirred cloud and dipole mode excitation of the cloud.We study superfluidity of a cigar-shaped Bose-Einstein condensate by stirring it with a Gaussian potential oscillating back and forth along the axial dimension of the condensate, motivated by experiments of Raman et al. [Phys. Rev. Lett. 83, 2502 (1999)]. Using classical-field simulations and perturbation theory, we examine the induced heating rate, based on the total energy of the system, as a function of the stirring velocity $v$. We identify the onset of dissipation by a sharply increasing heating rate above a velocity ${v}_{c}$, which we define as the critical velocity. We show that ${v}_{c}$ is influenced by the oscillating motion, the strength of the stirrer, the temperature, and the inhomogeneous density of the cloud. This results in a vanishing ${v}_{c}$ for the parameters similar to the experiments, which is inconsistent with the measurement of nonzero ${v}_{c}$. However, if the heating rate is based on the thermal fraction after a $100\phantom{\rule{4pt}{0ex}}\mathrm{ms}$ equilibration time, our simulation recovers the experimental observations. We demonstrate that this discrepancy is due to the slow relaxation of the stirred cloud and dipole mode excitation of the cloud.

arXiv:2110.14634Physical Review AApr 25, 202214 citations

Study of bose einstein condensates in superfluid regime

Priyanka Verma

Jan 1, 20130 citations

Probing superfluidity of Bose-Einstein condensates via laser stirring

Vijay Pal Singh, Wolf Weimer, Kai Morgener +5 more

We investigate the superfluid behavior of a Bose-Einstein condensate of $^{6}\mathrm{Li}$ molecules. In the experiment by Weimer et al. [Phys. Rev. Lett. 114, 095301 (2015)] a condensate is stirred by a weak, red-detuned laser beam along a circular path around the trap center. The rate of induced heating increases steeply above a velocity ${v}_{c}$ , which we define as the critical velocity. Below this velocity, the moving beam creates almost no heating. In this paper, we demonstrate a quantitative understanding of the critical velocity. Using both numerical and analytical methods, we identify the nonzero temperature, the circular motion of the stirrer, and the density profile of the cloud as key factors influencing the magnitude of ${v}_{c}$ . A direct comparison to the experimental data shows excellent agreement.We investigate the superfluid behavior of a Bose-Einstein condensate of $^{6}\mathrm{Li}$ molecules. In the experiment by Weimer et al. [Phys. Rev. Lett. 114, 095301 (2015)] a condensate is stirred by a weak, red-detuned laser beam along a circular path around the trap center. The rate of induced heating increases steeply above a velocity ${v}_{c}$, which we define as the critical velocity. Below this velocity, the moving beam creates almost no heating. In this paper, we demonstrate a quantitative understanding of the critical velocity. Using both numerical and analytical methods, we identify the nonzero temperature, the circular motion of the stirrer, and the density profile of the cloud as key factors influencing the magnitude of ${v}_{c}$. A direct comparison to the experimental data shows excellent agreement.

arXiv:1509.02168Physical Review AFeb 22, 201646 citations

v

. We identify the onset of dissipation by a sharply increasing heating rate above a velocity

{v}_{c}

, which we define as the critical velocity. We show that

{v}_{c}

is influenced by the oscillating motion, the strength of the stirrer, the temperature, and the inhomogeneous density of the cloud. This results in a vanishing

{v}_{c}

for the parameters similar to the experiments, which is inconsistent with the measurement of nonzero

{v}_{c}

. However, if the heating rate is based on the thermal fraction after a

100\phantom{\rule{4pt}{0ex}}\mathrm{ms}

equilibration time, our simulation recovers the experimental observations. We demonstrate that this discrepancy is due to the slow relaxation of the stirred cloud and dipole mode excitation of the cloud.

We investigate the superfluid behavior of a Bose-Einstein condensate of

^{6}\mathrm{Li}

molecules. In the experiment by Weimer et al. [Phys. Rev. Lett. 114, 095301 (2015)] a condensate is stirred by a weak, red-detuned laser beam along a circular path around the trap center. The rate of induced heating increases steeply above a velocity

{v}_{c}

, which we define as the critical velocity. Below this velocity, the moving beam creates almost no heating. In this paper, we demonstrate a quantitative understanding of the critical velocity. Using both numerical and analytical methods, we identify the nonzero temperature, the circular motion of the stirrer, and the density profile of the cloud as key factors influencing the magnitude of

{v}_{c}

. A direct comparison to the experimental data shows excellent agreement.