اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدLifetime of angular momentum in a rotating strongly interacting Fermi gas
592
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We investigate the lifetime of angular momentum in an ultracold strongly interacting Fermi gas, confined in a trap with controllable ellipticity. To determine the angular momentum we measure the precession of the radial quadrupole mode. We find that in the vicinity of a Feshbach resonance the deeply hydrodynamic behavior in the normal phase leads to a very long lifetime of the angular momentum. Furthermore, we examine the dependence of the decay rate of the angular momentum on the ellipticity of the trapping potential and the interaction strength. The results are in general agreement with the theoretically expected behavior for a Boltzmann gas.
قيم البحث
اقرأ أيضاً
We present a comprehensive study of the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer (BEC-BCS) crossover in fermionic $^6$Li using Bragg spectroscopy. A smooth transition from molecular to atomic spectra is observed with a clear signature of
pairing at and above unitarity. These spectra probe the dynamic and static structure factors of the gas and provide a direct link to two-body correlations. We have characterised these correlations and measured their density dependence across the broad Feshbach resonance at 834 G.
We report on measurements of an elementary surface mode in an ultracold, strongly interacting Fermi gas of 6Li atoms. The radial quadrupole mode allows us to probe hydrodynamic behavior in the BEC-BCS crossover without being influenced by changes in
the equation of state. We examine frequency and damping of this mode, along with its expansion dynamics. In the unitarity limit and on the BEC side of the resonance, the observed frequencies agree with standard hydrodynamic theory. However, on the BCS side of the crossover, a striking down shift of the oscillation frequency is observed in the hydrodynamic regime as a precursor to an abrupt transition to collisionless behavior; this indicates coupling of the oscillation to fermionic pairs.
The angular momentum of rotating superfluid droplets originates from quantized vortices and capillary waves, the interplay between which remains to be uncovered. Here, the rotation of isolated sub-micrometer superfluid 4He droplets is studied by ultr
afast x-ray diffraction using a free electron laser. The diffraction patterns provide simultaneous access to the morphology of the droplets and the vortex arrays they host. In capsule-shaped droplets, vortices form a distorted triangular lattice, whereas they arrange along elliptical contours in ellipsoidal droplets. The combined action of vortices and capillary waves results in droplet shapes close to those of classical droplets rotating with the same angular velocity. The findings are corroborated by density functional theory calculations describing the velocity fields and shape deformations of a rotating superfluid cylinder.
We study the expansion of a rotating, superfluid Fermi gas. The presence and absence of vortices in the rotating gas is used to distinguish superfluid and normal parts of the expanding cloud. We find that the superfluid pairs survive during the expan
sion until the density decreases below a critical value. Our observation of superfluid flow at this point extends the range where fermionic superfluidity has been studied to densities of 1.2 10^{11} cm^{-3}, about an order of magnitude lower than any previous study.
We study a rotating atomic Fermi gas near a narrow s-wave Feshbach resonance in a uniaxial harmonic trap with frequencies $Omega_perp$, $Omega_z$. Our primary prediction is the upper-critical angular velocity, $omega_{c2} (delta,T)$, as a function of
temperature $T$ and resonance detuning $delta$, ranging across the BEC-BCS crossover. The rotation-driven suppression of superfluidity at $omega_{c2}$ is quite distinct in the BCS and BEC regimes, with the former controlled by Cooper-pair depairing and the latter by the dilution of bosonic molecules. At low $T$ and $Omega_zllOmega_perp$, in the BCS and crossover regimes of $0 lesssim delta lesssim delta_c$, $omega_{c2}$ is implicitly given by $hbar sqrt{omega_{c2}^2 +Omega_perp^2}approx 2Delta sqrt{hbar Omega_perp/epsilon_F}$, vanishing as $omega_{c2} simOmega_perp(1-delta/delta_c)^{1/2}$ near $delta_capprox 2epsilon_{F} + fracgamma 2epsilon_{F} ln(epsilon_F/hbarOmega_perp)$ (with $Delta$ the BCS gap and $gamma$ resonance width), and extending bulk result $hbaromega_{c2} approx 2Delta^2/epsilon_{F}$ to a finite number of atoms in a trap. In the BEC regime of $delta < 0$ we find $omega_{c2} toOmega^-_perp$, where molecular superfluidity can only be destroyed by large quantum fluctuations associated with comparable boson and vortex densities.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
