Thomas Bland

Investigating vortices in dipolar quantum gases

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Following our recent experimental observation of vortices in Bose-Einstein condensates comprised of atoms with inherent long-range dipole-dipole interactions [Nat. Phys. 18, 1453-1458 (2022)], we thoroughly investigate vortex properties in the three-dimensional dominantly dipolar regime, where beyond-mean-field effects are crucial for stability, and investigate the interplay between trap geometry and magnetic field tilt angle. Last year, Jean Dalibard was awarded with the most prestigious French prize for physicists, the CNRS Gold medal, and this work is our contribution to a Special Issue honouring his many contributions to the field of ultracold atoms, and in particular his work on quantum vortices. See the full collection here: CNRS Gold Medal Jean Dalibard (academie-sciences.fr).

See the pre-print here: arXiv:2303.13263, and the now published paper here: C. R. Phys.

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 pre-print here: arXiv:2306.09698

Alex wins a PhD dissertation prize!

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Alex Patscheider, who finished his PhD with us last year, just received one of this year’s Hypo Tirol Prizes for his dissertation on controlling and understanding of dipolar quantum gases of erbium atoms.  Congratulations! 👏

Currently, Alex works as a Quantum Network Engineer at the Canada-based quantum technology company Photonic Inc.

Putting a supersolid under pressure

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In collaboration with colleagues from Otago, we investigate the excitation spectrum and compressibility of a dipolar Bose-Einstein condensate in an infinite tube potential in the parameter regime where the transition between superfluid and supersolid phases occurs. Our study focuses on the density range in which crystalline order develops continuously across the transition. Above the transition the superfluid shows a single gapless excitation band, phononic at small momenta and with a roton at a finite momentum. Below the transition, two gapless excitations branches (three at the transition point) emerge in the supersolid. We examine the two gapless excitation bands and their associated speeds of sound in the supersolid phase. Our results show that the speeds of sound and the compressibility are discontinuous at the transition, indicating a second-order phase transition. These results provide valuable insights into the identification of supersolid phenomena in dipolar quantum gases and the relationship to supersolidity in spin-orbit coupled gases.


See the pre-print here: arXiv:2306.04794

Heating a liquid into a… solid?!

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Raising the temperature of a material enhances the thermal motion of particles. Such an increase in thermal energy commonly leads to the melting of a solid into a fluid and eventually vaporises the liquid into a gaseous phase of matter. Here, together with theorists from Aarhus, Denmark, we study the finite-temperature physics of dipolar quantum fluids and find surprising deviations from this general phenomenology. In particular, we describe how heating a dipolar superfluid from near-zero temperatures can induce a phase transition to a supersolid state with a broken translational symmetry. The predicted effect agrees with our experimental measurements from the Er-Dy, which opens the door for exploring the unusual thermodynamics of dipolar quantum fluids.



See the pre-print here: arXiv:2209.00335 and the published paper here: Nature Communications (2023)

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