A Thouless pump with dipolar interactions

Thouless pumping represents a powerful concept to probe quantized topological invariants in quantum systems. We explore this mechanism in a generalized Rice-Mele Fermi-Hubbard model characterized by the presence of competing onsite and intersite interactions. While large on-site repulsion leads to a breakdown of quantized pumping , sufficiently large intersite interactions allow for an interaction-induced recovery of Thouless pumps. The stable topological transport at large interactions is connected to the presence of a spontaneous bond-order-wave in the ground-state phase diagram of the model. We also discuss a concrete experimental setup based on ultracold magnetic atoms in an optical lattice.

The article can be found here: Quantum, the pre-print can be accessed here: arXiv

A very excited dipolar quantum droplet

Now published in PRL!  Together with collaborators from the University of Otago, we present the the excitation spectrum of Erbium at the crossover from a Bose-Einstein condensate to a trapped macrodroplet. The measurements coincide well with the predictions and confirm the peculiar features of this spectrum: a strong upward shift in energy at low momentum and the appearance of multiple excitation branches at higher momentum. It turns out that these features can be explained by the tendency of the excitations to avoid the central dense part of the droplet and by becoming more like ripples moving over the surface of a droplet!

Read it in Physical Review Letters, Phys. Rev. Lett. 132, 103401,  and see the pre-print here: arXiv:2308.00003.

A Thouless pump with dipolar interactions

Thouless pumping represents a powerful concept to probe quantized topological invariants in quantum systems. We explore this mechanism in a generalized Rice-Mele Fermi-Hubbard model characterized by the presence of competing onsite and intersite interactions. While large on-site repulsion leads to a breakdown of quantized pumping , sufficiently large intersite interactions allow for an interaction-induced recovery of Thouless pumps. The stable topological transport at large interactions is connected to the presence of a spontaneous bond-order-wave in the ground-state phase diagram of the model. We also discuss a concrete experimental setup based on ultracold magnetic atoms in an optical lattice.

The pre-print can be accessed here: arXiv

A very excited dipolar quantum droplet

Now published in PRL!  Together with collaborators from the University of Otago, we present the the excitation spectrum of Erbium at the crossover from a Bose-Einstein condensate to a trapped macrodroplet. The measurements coincide well with the predictions and confirm the peculiar features of this spectrum: a strong upward shift in energy at low momentum and the appearance of multiple excitation branches at higher momentum. It turns out that these features can be explained by the tendency of the excitations to avoid the central dense part of the droplet and by becoming more like ripples moving over the surface of a droplet!

Read it in Physical Review Letters, Phys. Rev. Lett. 132, 103401,  and see the pre-print here: arXiv:2308.00003.

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

Bloch oscillations and matter-wave localization in erbium!

We study Er atoms in a one-dimensional lattice. We use Bloch oscillations to evaluate the role played by the different interaction terms, and in particular by the quantum fluctuations. We additionally observe a transition–driven by interactions–to a state localized to a single lattice plane. To benchmark our results, we developed a discrete one-dimensional extended Gross-Pitaevskii theory. This model is in quantitative agreement with the experiment, additionally revealing, in our parameter regime, the existence of many different phases: macrodroplets occupying single or many lattice sites and two-dimensional bright solitons.

See the open access paper here: Commun. Phys. 5, 227 (2022)