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Dipolar condensed atomic mixtures and miscibility under rotation
by Lauro Tomio, R. Kishor Kumar and Arnaldo Gammal
This is not the current version.
|As Contributors:||LAURO TOMIO|
|Submitted by:||TOMIO, LAURO|
|Submitted to:||SciPost Physics Proceedings|
|Proceedings issue:||24th European Few Body Conference (University of Surrey, U.K.)|
|Subject area:||Quantum Physics|
By considering symmetric and asymmetric dipolar coupled mixtures (with dysprosium and erbium isotopes), we report a study on relevant anisotropic effects, related to spatial separation and miscibility, due to dipole-dipole interactions (DDIs) in rotating binary dipolar Bose-Einstein condensates. The binary mixtures are kept in strong pancake-like traps, with repulsive two-body interactions modeled by an effective two-dimensional (2D) coupled Gross-Pitaevskii equation. The DDI are tuned from repulsive to attractive by varying the dipole polarization angle. A clear spatial separation is verified in the densities for attractive DDIs, being angular for symmetric mixtures and radial for asymmetric ones. Also relevant is the mass-imbalance sensibility observed by the vortex-patterns in symmetric and asymmetric-dipolar mixtures. In an extension of this study, here we show how the rotational properties and spatial separation of these dipolar mixture are affected by a quartic term added to the harmonic trap of one of the components.
Submission & Refereeing History
Reports on this Submission
Anonymous Report 1 on 2019-11-22 Invited Report
1. The study of ultracold dipolar mixtures, in particular dipolar condensates, is a timely problem, and this contribution points to interesting options to control the miscibility/overlap of such two-component systems.
2. The variety of parameters explored provide a broad overview of the options offered by theses systems, with realistic parameters, and a relevant choice of atomic species.
3. The problem, methods and results are presented in a succinct and clear manner.
1. There is not much discussion about how the quartic potential could be created in practice, and why it would affect only (or mostly) the heavier species. While for the Er-Dy mixture it is clear that this may help invert the inside-outside densities, for the Dy-Dy mixture the situation is less clear. If this additional trapping energy is considered to be due to the same trapping laser creating the harmonic confinement, it would appear that it should affect the lighter species more, as this is the one that will generally explore a larger spatial region.
This manuscript presents a detailed numerical study of the miscibility properties of two-component dipolar condensates in both harmonic and harmonic + quartic potentials, under rotation.
Specifically, the authors have considered mixtures of two dysprosium isotopes, or a dysprosium isotope with an erbium isotope. The same authors have recently reported on the distinct miscibility properties of these two mixtures due to the differing role of contact interactions, which lead to a broad variety of density profiles for the two systems as a function of rotation velocity and of the strength of the dipole-dipole interaction. Here, they show how these density profiles can be modified by adding a quartic potential that affects one of the two species, namely the heavier one in each case.
The main finding in the present manuscript is the possibility to affect the pattern of density distribution in both 'symmetric' and 'asymmetric' mixtures by controlling the additional quartic potential. In particular, the authors show it is possible to (i) induce the lead to radial phase separation [in particular, the appearance of the 'ring lattice'] in the Dy-Dy mixture [Fig. 1], and (ii) reverse the inner-outer density imbalance in the Er-Dy mixtures [Figs. 3 and 4], in contrast to the observations in their earlier work without quartic potential. These suggestions may be of interest to ongoing experimental efforts.
Because of the timeliness of this work, together with the broad range of parameters studied with well-established numerical techniques, I recommend publication of this manuscript in SciPost Physics Proceedings.
1. The authors should introduce earlier on what they mean by "symmetric" and "asymmetric" mixtures. This is done only on page 5 (lines 166-167), when the concepts have been used much earlier in the text.
2. The authors should provide some statement on the potential way to generate a controllable quartic potential in practice (e.g., an additional laser detuned from a particular transition of one species, so as to affect only that one?).
3. The authors could indicate the advantages, if any, of calculating the dipole-interaction term by moving to momentum (Fourier) space. Does this provide any numerical advantage?