Rotating a Supersolid Dipolar Gas

Abstract

Distintictive features of supersolids show up in their rotational properties. We calculate the moment of inertia of a harmonically trapped dipolar Bose-Einstein condensed gas as a function of the tunable scattering length parameter, providing the transition from the (fully) superfluid to the supersolid phase and eventually to an incoherent crystal of self-bound droplets. The transition from the superfluid to the supersolid phase is characterized by a jump in the moment on inertia, revealing its first order nature. In the case of elongated trapping in the plane of rotation we show that the the moment of inertia determines the value of the frequency of the scissors mode, which is significantly affected by the reduction of superfluidity in the supersolid phase. The case of isotropic trapping is instead well suited to study the formation of quantized vortices, which are shown to be characterized, in the supersolid phase, by a sizeable deformed core, caused by the presence of the sorrounding density peaks.

Vortex properties in the extended supersolid phase of dipolar Bose-Einstein condensates

“…7. It appears that the core is very deformed following the symmetry of the interstitial site [34]. We have found a similar vortex-core structure for other values of the scattering length.…”

“…2. In this phase, the lowestenergy position of the vortex core is in the interstitial region between three adjacent droplets, where the local particle density ρ(r) is very small, so that the energy cost of the additional depression of ρ(r) near the vortex core (remember that the local density has to vanish at the vortex core) is minimized and the kinetic energy of the superfluid flow around the vortex core also decreases [34]. To visualize the vortex-core structure, the map of the difference between the densities of the configuration with and without vortex at the interstitial site for the a s = 93 a 0 case is shown in the upper panel of Fig.…”

“…Most of the recent evidence of supersolid behavior in dipolar gases is based on the identification of two main features of a SSP, i.e., (i) a nonzero, nonclassical translational and rotational inertia [36] and (ii) the appearance of the Nambu-Goldstone gapless mode [37] corresponding to phase fluctuations-besides the phonon mode associated to density fluctuations which results from the translational discrete sym-metry of the system. But no evidence of another hallmark of superfluidity has been gathered so far, namely, the presence of quantized vortices [34]. Experimental realization and detection of quantized vortices would provide a direct evidence of global coherence in the SSP of a dipolar system.…”

Self-bound supersolid stripe phase in binary Bose-Einstein condensates

“…This new form of self-bound, ultradilute quantum matter has already revealed a range of unexpected phenomena. Prominent examples are the pattern formation of quantum ferrofluidic droplets [8][9][10] shaped by the long-range anisotropic dipolar interaction, or the recent evidence for supersolidity [16][17][18][19][20][21].…”

Kolmogorov and Kelvin wave cascades in a generalized model for quantum turbulence

“…In helium and other superfluids, the interaction between bosons is stronger and high-order nonlinearities are needed for proper modeling. For instance, in helium high-order terms are considered to mimic its equation of state [25] and in dipolar BECs beyond mean field terms are needed to describe the physics of recent supersolid experiments [34].…”