## "Competing interactions in dipolar erbium atoms"
Ultracold magnetic atoms exhibit short-range contact interactions together with long-range dipole-dipole interactions. The competition between these two interactions gives rise to various quantum phases [1], where the usually dominant mean-field interactions are small and the system is governed by quantum fluctuations [2]. In this talk, I will first report on the study of a supersolid state and its excitation spectrum [3]. In such a state, two symmetries are spontaneously broken: the gauge symmetry, associated with the phase coherence of a superfluid, and the translational invariance, signalizing crystalline order. As a result, two distinct branches appear in the excitation spectrum, one for each broken symmetry. In the second part of the talk, we add a one-dimensional optical lattice to the system and create a platform, in which quantum fluctuations are still unexplored and a variety of new phases may be observable. We employ Bloch oscillations as an interferometric tool to assess the role that quantum fluctuations play in an array of quasi-two- dimensional Bose-Einstein condensates [4]. We observe a transition to a state localized into a single lattice site purely driven by interactions. Finally, we uncover the parameter regimes where both droplet and soliton states can be achieved. [1] L. Chomaz, I. Ferrier-Barbut, F. Ferlaino, B. Laburthe- Tolra, B. L. Lev, and T.Pfau, Dipolar physics: A review of experiments with magnetic quantum gases. ArXiv: 2201.02672 (2022) [2] A. R. P. Lima and A. Pelster, Beyond mean-field low- lying excitations of dipolar Bose gases, Phys.Rev. A 86, 063609 (2012) [3] G. Natale, R.M.W. van Bijnen, A. Patscheider, D. Petter, M.J. Mark, L. Chomaz, and F. Ferlaino, Excitation Spectrum of a Trapped Dipolar Supersolid and Its Experimental Evidence, Phys. Rev. Lett. 123, 050402 (2019) [4] G. Natale, T. Bland, S. Gschwendtner, L. Lafforgue, D. S. Grun, A. Patscheider, M. J. Mark and F. Ferlaino, Bloch oscillations and matter-wave localization of a dipolar quantum gas in a one dimensional lattice, Comm. Phys. 5, 227 (2022) Host: Ricardo Diez Muino Note: This lecture is part of the joint session with talk by Claudia Politi scheduled at 12:00 p.m. |