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Physics Seminar - Dr Lauriane Chomaz

Thursday, 4 July 2019

Physics Department

Dr Lauriane Chomaz

Institute for Experimental Physics

University of Innsbruck

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

Although very dilute, the behavior of ultracold atomic gases is fundamentally determined by the interparticle interactions. For most of the atomic species, these interactions are short-ranged and isotropic, yielding a simple yet very powerful description based on contact pseudopotentials. In the aim of enriching the physics at play, efforts have been dedicated to produce ultracold gases with additional long-range and anisotropic interactions. The Innsbruck group, of which I am now part, made a major contribution in this direction by achieving quantum degeneracy of a highly magnetic lanthanide atom, erbium, in 2012, just after that of dysprosium in 2011.

Quantum gases of highly magnetic lanthanide atoms have become a very successful platform, in which a wide variety of dipolar-related phenomena have been explored. In particular, within the last few years, experiments proved the existence of several exotic many-body states in quantum degenerate Bose dipolar gases.

A special type of elementary excitations of the gas, forming a local energy minimum at finite momentum in the dispersion relation, was observed. This excitation is reminiscent of the famous roton mode in superfluid helium and relates the dipolar gas to this strongly correlated fluid. In the experiment, we have demonstrated the softening of the dipolar roton excitation when tuning the interaction strength, precursor of a crystallization. We have probe the roton excitation both in the stable and the instable regimes, in which we observed the dynamical population of the mode after an interaction quench.

The underlying phase diagram, beyond the mean-field instability, have also been explored in a wide variety of experiments. Quantum stabilized single-droplet states and droplet-assembly states have been observed in various settings. Most recently, droplet-assembly states showing hallmarks of supersolidity were observed in a limited interaction-strength regime close to the instability threshold were observed, in particular in our group.

In my talk, I will review our studies of these intriguing many-body states, presenting their current status and highlighting the future prospects.

WHEN: Thursday 4 July 2019
WHERE: Room 314, Science 3 Building
TIME: 3.00 pm–4.00 pm

All interested are welcome to attend

Light refreshments to follow in Common Room