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Details der Veranstaltung:

2019-11-27 [ ]

Talk with Ms. Chomaz on November 29th

Topic: From roton excitations to supersolid behaviors in quantum Bose gases of highly magnetic atoms

Based on their strong long-range and anisotropic dipole-dipole interactions, highly magnetic lanthanide atoms have been one of the most thriving platforms to study many-body physics in ultracold gases. Within the last few years, experiments using these atoms proved exotic phenomena, in particular the existence of novel many-body states, in dipolar gases. In Ms. Chomaz's talk, she will report on the results of her group in Innsbruck, investigating quantum degenerate Bose gases of erbium and dysprosium atoms.

In erbium gases, her group has observed a special type of elementary excitations, forming a local energy minimum at finite momentum in the dispersion relation, reminiscent of the roton excitation in superfluid helium. In the dipolar case, the roton excitation results from the interplay between the dipole interaction and the gas geometry. They have demonstrated the softening of this excitation when tuning the interaction strength, precursor of a crystallization. They have probe the roton excitation both in the stable and the instable regime, in which we observed the dynamical population of the mode after an interaction quench. They explored the underlying phase diagram, beyond the mean-field instability. Here, we were able to observe both transient and long-lived supersolid behaviors in a limited interaction-strength regime close to the instability threshold, using erbium and dysprosium quantum gases. In the long-lived dysprosium case, they were able to reach the state with supersolid properties by evaporative cooling starting from a thermal sample. Most recently, they also performed first experiments probing the elementary excitations of those gases, providing first hints of superfluid phase flow in the supersolid. Their results pave the way to future studies of the peculiar behavior of supersolid stationary states in dipolar quantum gases.

Laurian Chomaz from University of Innsbruck will talk on the topic on the 29th of November, 15:30 at the Hörsaal of the Atominstitut at Stadionallee 2, 1020 Wien. The invitation with all the details can be found here.