Erbium Scientific News

Category for scientific news of the Erbium group

A Thouless pump with dipolar interactions

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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

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In this preprint, we present together with collaborators from the University of Otago 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!

See the pre-print here: arXiv:2308.00003.

Review of recent experiments with dipolar gases

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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!

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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)

Revealing the topological nature of the bond order wave in a strongly correlated quantum system

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Now published in PRR with collaborators from ICFO, Barcelona! In the recent years, great effort has been devoted toward the study of symmetry-protected topological phases. We show that the bond order wave (BOW) induced by frustration between competing couplings has a nontrivial topological sector in the presence of chiral symmetry. We reveal its topological nature by finding a nonzero string order correlator and a degenerate entanglement spectrum, and design a realistic experimental scheme involving magnetic atoms trapped in an optical lattice. The latter paves the way towards an efficient quantum simulation of topological phases in many-body quantum systems.

The paper can be accessed here: Phys. Rev. Research, and the pre-print here: arXiv

Determination of the scattering length of erbium atoms

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Now published in PRA with collaborators from JILA, Boulder (Colorado, USA), we accurately determine the scattering length for the four bosonic erbium isotopes with highest abundance in the magnetic field range from 0G to 5G. We use the cross-dimensional thermalization technique and extract the scattering length by applying a fit of the complete Enskog equations of change and by utilizing an analytic formula for the so-called number of collisions per re-thermalization. We benchmark our results with the very accurate but experimentally more demanding lattice modulation spectroscopy, confirming the accuracy of our experimental protocol.

The paper can be accessed here: Phys. Rev. A, and the pre-print here: arXiv

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