Hannover 2020 – scientific programme

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A: Fachverband Atomphysik

A 17: Ultracold atoms, ions, and BEC IV (joint session A/Q)

A 17.6: Talk

Wednesday, March 11, 2020, 12:30–12:45, f303

Rotons and Maxons in a Rydberg-Dressed Bose-Einstein Condensate — •Gary McCormack¹, Rejish Nath², and Weibin Li¹ — ¹School of Physics and Astronomy, and Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems, Nottingham, UK — ²Indian Institute of Science Education and Research, Pune, India

We investigate a three-dimensional Bose-Einstein condensate with a long-range soft-core two-body interaction. This interaction is induced by laser coupling the condensed atom to a highly excited Rydberg state off-resonantly. We show that the long-range interaction drastically alters the dispersion relation, giving rise to both roton and maxon modes. While rotons are typically responsible for density modulations throughout the system, maxons are normally unstable and hence decay quickly once excited, as predicted in dipolar condensates. We show that maxon modes in the Rydberg-dressed condensate, on the contrary, is stable in the dynamics. We provide a scheme to trigger the maxon mode through a quench, i.e. suddenly activation of the strong soft-core interaction. The emergence of the maxon is accompanied by persistent, high frequency oscillations in the quantum depletion, while rotons cause much slower oscillations. Through a self-consistent Bogoliubov approach, we identify the dependence of maxon modes on the soft-core interaction. We also reveal how the maxons will modify the dynamics of density-density correlations and number fluctuations of the condensate. Our study paves a new route to probe exotic quasiparticles in ultracold Bose gases with Rydberg-dressed long-range interactions.