Dancing supersolids synchronize

 

In collaboration between the Er-Dy Lab and the Theory subgroup, and Dr. Giacomo Lamporesi at the BEC centre in Trento, our new pre-print reveals a fundamental difference in a supersolid’s response to rotation in absence or presence of a quantum vortex. This work builds on our previous investigation of vortices in supersolids, showing that the superfluid and solid natures synchronize to the external rotation only when there are vortices in the state. We verify this theoretical prediction in the experiment, revealing the route to vortex nucleation in supersolids.

See the pre-print here: https://arxiv.org/abs/2412.11976

Vortices in a dipolar supersolid

 

Now published in Nature!

In an internal collaboration between the Er-Dy Lab and the Theory subgroup, our new pre-print reveals a fundamental difference in vortex nucleation between the unmodulated superfluid and the modulated 2D supersolid phase of dipolar BECs. This work builds on our previous investigation of vortices in dipolar gases (see our writeups here and here) and of supersolids with two-dimensional crystalline order (see our writeup here). This opens the door to study the hydrodynamic properties of exotic quantum systems with multiple spontaneously broken symmetries, ranging from quantum crystals to neutron stars — for a general overview of the connection between glitches in the supersolid and neutron stars, see our writeup here.

See the article in Nature here: Observation of vortices in a dipolar supersolid

Read the pre-print here: arXiv:2403.18510.

Read the feature by Quanta Magazine here: Physicists spot quantum tornadoes twirling in a supersolid

Excitations of a two-dimensional supersolid

Now published in the journal “Physical Review A”!  The newest work from the Theory group are the results of PhD student Elena Poli’s DK-ALM research stay abroad in the group of Professor Blair Blakie at the University of Otago, NZ. In this theory paper, they study the excitations and elastic parameters of the 2D supersolid state of a BEC with dipolar interactions and soft-core interactions. See the following excerpt from the abstract for some of the details of this collaborative effort:

[The] supersolid state has three gapless excitation branches arising from the spontaneously broken continuous symmetries. Two of these branches are related to longitudinal sound waves, similar to those in one-dimensional supersolids. The third branch is a transverse wave arising from the non-zero shear modulus of the two-dimensional crystal. We present the results of numerical calculations for the excitations and dynamic structure factor characterising the density fluctuations, and study their behavior across the discontinuous superfluid to supersolid transition. We show that the speeds of sound are described by a hydrodynamic theory that incorporates generalized elastic parameters, including the shear modulus. Furthermore, we establish that dipolar and soft-core supersolids manifest distinct characteristics, falling into the bulk incompressible and rigid lattice limits, respectively.

See the article in PRA here: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.053301
See the pre-print here: Excitations of a two-dimensional supersolid https://arxiv.org/abs/2407.01072.

Spektrum magazine article: glitches in supersolids and neutron stars for Sterne und Weltraum

For German speakers: in this month’s edition of ‘Sterne und Weltraum’ of Spektrum magazine, you will find an article  about the links between glitches in supersolids and in neutron stars, written by our very own Elena Poli, Thomas Bland, Manfred Mark, and Francesca Ferlaino, alongside frequent collaborator, Massimo Mannarelli.

Read the article here: https://www.spektrum.de/news/pulsare-quantenwirbel-beschleunigen-neutronensterne/2206793

Binary supersolids get exciting

Now published in Physical Review Letters! With colleagues here in Innsbruck and at the University of Otago, NZ, we predict a rich excitation spectrum of a binary dipolar supersolid in a linear crystal geometry, where the ground state consists of two partially immiscible components with alternating, interlocking domains. We identify three Goldstone branches, each with first-sound, second-sound or spin-sound character. In analogy with a diatomic crystal, the resulting lattice has a two-domain primitive basis, and we find that the crystal (first-sound-like) branch is split into optical and acoustic phonons. We also find a spin-Higgs branch that is associated with the supersolid modulation amplitude.


See the paper here: PhysRevLett.133.103401 and arXiv:2312.03390

Pinning dynamics of vortices in a dipolar supersolid

ImageNow published in the journal “Few-Body Systems”! Together with collaborators at Laboratori Nazionali del Gran Sasso, we investigate the pinning dynamics of vortices in rotating dipolar supersolids. This work is a follow-up our paper last year on how glitches in the supersolid serve as a versatile analogue of the same behaviour in neutron stars.

See the paper here: Few Body Systems, arxiv.org/abs/2407.03212