Following our recent experimental observation of vortices in Bose-Einstein condensates comprised of atoms with inherent long-range dipole-dipole interactions [Nat. Phys. 18, 1453-1458 (2022)], we thoroughly investigate vortex properties in the three-dimensional dominantly dipolar regime, where beyond-mean-field effects are crucial for stability, and investigate the interplay between trap geometry and magnetic field tilt angle. Last year, Jean Dalibard was awarded with the most prestigious French prize for physicists, the CNRS Gold medal, and this work is our contribution to a Special Issue honouring his many contributions to the field of ultracold atoms, and in particular his work on quantum vortices. See the full collection here: CNRS Gold Medal Jean Dalibard (academie-sciences.fr).

See the pre-print here: arXiv:2303.13263, and the now published paper here: C. R. Phys.

# Er-Dy Scientific News

Category for scientific news of the Er-Dy group

## A ship-in-a-bottle quantum gas microscope

Quantum gas microscopes are versatile and powerful tools to investigate lattice systems down to the single atom level. Here we present a quantum gas microscopy setup for experiments with highly magnetic atoms of the lanthanoid elements erbium and dysprosium. Our setup features a quartz glass cell, enclosed by a compact multi-shell ferromagnetic shield. Inside, a non-magnetic, non-conducting, large-working-distance, high-numerical-aperture, in-vacuum microscope objective will enable single-site imaging of our strongly dipolar atomic mixture.

See the pre-print here: arXiv:2306.05404

## Heating a liquid into a… solid?!

Raising the temperature of a material enhances the thermal motion of particles. Such an increase in thermal energy commonly leads to the melting of a solid into a fluid and eventually vaporises the liquid into a gaseous phase of matter. Here, together with theorists from Aarhus, Denmark, we study the finite-temperature physics of dipolar quantum fluids and find surprising deviations from this general phenomenology. In particular, we describe how heating a dipolar superfluid from near-zero temperatures can induce a phase transition to a supersolid state with a broken translational symmetry. The predicted effect agrees with our experimental measurements from the Er-Dy, which opens the door for exploring the unusual thermodynamics of dipolar quantum fluids.

See the pre-print here: arXiv:2209.00335 and the published paper here: Nature Communications (2023)

## Review of recent experiments with dipolar gases

The last 15 years has seen tremendous experimental progress for the manipulation and control of ultracold atoms with sizeable dipole-dipole interactions. In this review, together with other group leaders who first condensed dysprosium and chromium, we review the discoveries made so far, and lay out the future perspectives for this exciting field!

The paper can be found here: Dipolar physics: a review of experiments with magnetic quantum gases – IOPscience

## Quantum vortices in a dipolar gas!

We report on the observation of vortices in a dysprosium quantum gas! Together with Dr. Giacomo Lamporesi from the University of Trento, we investigate one of the most fundamental phenomenon of superfluidity: quantized vorticity. We exploit the anisotropic nature of the dipole-dipole interaction to induce angular symmetry breaking in an otherwise cylindrically symmetric pancake-shaped trap. Tilting the magnetic field towards the radial plane deforms the cloud into an ellipsoid through magnetostriction, which is then set into rotation. At stirring frequencies approaching the radial trap frequency, we observe the generation of dynamically unstable surface excitations, which cause angular momentum to be pumped into the system through vortices. In the image above, if we keep the magnetic field tilted whilst rotating the vortices arrange into a stripe configuration along the field–in close corroboration with simulations–realizing a long sought-after prediction for dipolar vortices. Tilting the field back up the vortices lose this alignment, and become isotropic in shape.

Check out the paper in Nature Physics here: Nat. Phys. The paper is also twinned with a nice write-up from Prof. Zoran Hadzibabic from the University of Cambridge, titled “When ultracold magnets swirl“

## Can Angular Oscillations Probe Superfluidity in Dipolar Supersolids?

Now published in PRL! In a new joint theory-experimental collaboration, we investigate the extent that angular oscillations of a dipolar supersolid can tell us about the superfluidity of the system. Previous investigations of this been confined to linear droplet arrays.

Here, together with Prof. Luis Santos at the University of Hannover, we explore angular oscillations in systems with 2D structure, which in principle have greater sensitivity to superfluidity. Surprisingly, in both experiment and simulation, we find that the frequency of angular oscillations remains nearly unchanged even when the superfluidity of the system is altered dramatically. Indicating that angular oscillation measurements do not always provide a robust experimental probe of superfluidity with typical experimental protocols.

The paper can be accessed here: PRL 129, 040403 and the preprint here: arXiv:2111.07768