Two-dimensional supersolidity in a circular trap

Figure: Experimental realisation of a two-dimensional seven droplet hexagon state. (a) In-situ image of density profile. (b) Image after 36 ms time-of-flight expansion. (c,d) Corresponding theory result for the same trap. In (d), the time-of-flight expansion is estimated by a Fourier transform of the wavefunction.

Dipolar condensates were recently coaxed into supersolid phases supporting both superfluid and crystal excitations. The first dipolar supersolids consisted of one dimensional droplet arrays, and a recent experiment here achieved two dimensional supersolidity, observing the transition from a linear chain to a zig-zag configuration of droplets.

In this work, in collaboration with Prof. Luis Santos from the Leibniz University Hannover, we show that while one-dimensional supersolids may be prepared from condensates via a roton instability, such a procedure in two dimensions tends to destabilise the supersolid. By evaporatively cooling directly into the supersolid phase–hence bypassing the roton instability–we experimentally produce a 2D supersolid in a near-circular trap, an observation verified through state-of-the-art finite temperature simulations. We show that 2D roton modes have little in common with the supersolid configuration, instead, unstable rotons produce a small number of central droplets, which triggers a nonlinear process of crystal growth. We calculate excitations for a 2D supersolid ground state, and make comparisons with 1D arrays using the static structure factor. These results provide insight into the process of supersolid formation in 2D, and define a realistic path to the formation of large two-dimensional supersolid arrays.

This work is on the arXiv, and a PDF can be found here.

Lifecycle of a Supersolid Featured in APS Physics Viewpoint and Physics World

Congratulation to Max, Claudia, Lauritz, Lauriane, Manfred and Matt for their experimental work

on the lifecycle of a supersolid, which has been just published in Phys. Rev. Lett..

The paper got selected as Editors’ Suggestion by APS and featured in Physics Viewpoint and in Physics World.

Read More:

Research News: Physics Viewpoint article by Chinmayee Mishra, entitled  “Cooling a Thermal Cloud to a Supersolid”.

Research News: Physics World article by Oliver Stockdale, entitled “High-resolution imaging sheds light on supersolid formation

Reference:

Birth, Life, and Death of a Dipolar Supersolid

Maximilian Sohmen, Claudia Politi, Lauritz Klaus, Lauriane Chomaz, Manfred J. Mark, Matthew A. Norcia, and Francesca Ferlaino

Phys. Rev. Lett. 126, 233401 (2021)

Published June 7, 2021

Elected member of the ÖAW

In recognition of her outstanding achievements, Francesca Ferlaino was elected a Corresponding Member of the Mathematical and Natural Sciences Class of the Austrian Academy of Sciences.

The Austrian Academy of Sciences (ÖAW) strengthens its ranks with 31 newly elected members. In this year’s elections, 19 female and 12 male researchers from a wide variety of disciplines in the humanities, social and cultural sciences as well as mathematics, natural and technical sciences were awarded membership in the ÖAW for their outstanding scientific achievements. Francesca Ferlaino’s research explores quantum phenomena in atomic gases at ultralow temperatures with contributions spanning topics including quantum matter of atoms and molecules and few-body and scattering physics. Her work has earned her multiple awards, including the prestigious Feltrinelli Prize, the Grand Prix de Physique “Cécile-DeWitt Morette/École de Physique des Houches” from the French Academy of Sciences, the Junior BEC Award, and the Erwin Schrödinger Prize, the highest award of the Austrian Academy of Sciences. In addition, she is recipient of an Alexander-von-Humboldt Professorship, a START-Prize and two ERC Grants (Starting and Consolidator).

Phase coherence in out-of-equilibrium supersolid states of ultracold dipolar atoms

Now in Nature Physics!

Supersolids are fluid and solid at the same time. In jointly collaboration work, together with Thierry Giamarchi, theoretical physicist from the University of Geneva, we have for the first time investigated what happens when such a state is brought out of balance.

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