Abstract:

Droplets are very common in nature, from liquid water to superfluid Helium and nuclear matter. In this talk I will discuss two examples of stable self-bound solutions exist in dipolar gases and Rabicoupled BECs. In the first part I will present the zero temperature phase diagram of bosons interacting via dipolar interactions in three dimensions in free space. Upon increasing the strength of the dipolar interaction and at sufficiently high densities we find a wide region where filaments are stabilized along the direction of the external field. Most interestingly by computing the superfluid fraction we conclude that superfluidity is anisotropic and vanishes along the orthogonal plane. In the second part I will focus on the case of two-component Bose condensates coupled via a laser field. We study the effects of quantum fluctuations on a Rabi-coupled two-component Bose gas of interacting alkali atoms. The divergent zero-point energy of gapless and gapped elementary excitations of the uniform system is properly regularized obtaining a meaningful analytical expression for the beyondmean- field equation of state. In the case of attractive inter-particle interaction we show that the quantum pressure arising from Gaussian fluctuations can prevent the collapse of the mixture with the creation of a self-bound droplet. We characterize the droplet phase and discover an energetic instability above a critical Rabi frequency provoking the evaporation of the droplet. Finally, we suggest an experiment to observe such quantum droplets using Rabi-coupled internal states of 39K atoms and measure their collective excitations.

Keywords: Clusters; Droplets; Mixtures; Dipoles.

References

1. A. Cidrim, F. E. A. dos Santos, E. A. Henn, T. Macrì, Vortices in self-bound dipolar droplets, Phys. Rev. A 98, 023618 (2018).

2. A. Cappellaro, T. Macrì, G. F. Bertacco and L. Salasnich, Equation of state and self-bound droplet in Rabicoupled Bose mixtures, Scientific Reports 7, 13358 (2017).

3. F. Cinti, A. Cappellaro, L. Salasnich and T. Macrì, Superfluid filaments of dipolar bosons in free space, Phys. Rev. Lett. 119, 215302 (2017).

Coffee/tea and cake from 15:00