Theory Scientific News

Category for scientific news related to the theory group.

Excitations of a two-dimensional supersolid

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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

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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

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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

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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

Der Suprafestkörper: a popular science article on the dipolar supersolid!

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imageIf you have been searching for a high-level overview of the dipolar supersolid phase, look no further than this open access article by Prof. Francesca Ferlaino and Dr. Manfred Mark! Newly published in the journal “Physik in unserer Zeit”, this German language primer lays out the historical background, newly discovered properties and open questions which remain about this paradoxical quantum phase. See the full article below:

Ferlaino, F. and Mark, M.J. (2024), Der Suprafestkörper. Phys. Unserer Zeit. https://doi.org/10.1002/piuz.202301692

Supersolids and… neutron stars?!

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With colleagues from LNGS and Gran Sasso Science Institute (L’Aquila, Italy), we show that rotating dipolar quantum gases in the supersolid phase can serve as a versatile analogues of neutron stars effectively emulating their behaviour during a glitch, an occasional abrupt speed up of a highly magnetic neutron star’s rotation frequency, followed by a slow relaxation. In rotating neutron stars, glitches are believed to occur when many superfluid vortices unpin from the interior, transferring angular momentum to the stellar surface. In the supersolid analogy, we show that a glitch happens when vortices pinned in the low-density inter-droplet region abruptly unpin. We show that dipolar supersolids offer an unprecedented possibility to test both the vortex and crystal dynamics during glitches events and they provide a tool to study glitches originating from different radial depths of a neutron star. Benchmarking our theory against neutron star observations, these results will open a new avenue for the quantum simulation of stellar objects from Earth.


See the paper here: Phys. Rev. Lett., arXiv:2306.09698

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