Monopoles, Alice rings and topological interfaces in a quantum fluid

Abstract: Vortices are common natural phenomena, from turbulence in fluids to atmospheric cyclones. In quantum fields, they can emerge with discrete values of circulation. These are topological excitations (TEs), predicted from symmetry arguments alone and showing striking similarities, from quantum fluids, to condensed matter physics and cosmology. Advancements in ultracold atomic physics are prospecting the controlled creation of previously inaccessible TEs in magnetic quantum fluids known as spinor Bose-Einstein condensates (BECs).

In this seminar, I will address TEs and their dynamics in a spin-2 BECs, where the rich variety of order-parameter symmetries allows exotic phenomena such as fractional vortex charges, monopoles, and non-singular spin textures. In particular, I will show how energy relaxation causes a monopole in the uniaxial-nematic phase to deform into a spin-Alice ring, exhibiting a composite core with distinct short- and long-distance topologies [1]. Numerical simulations reveal dynamical oscillations between the spin-Alice ring and a split-core hedgehog configuration. Moreover, I will also address TEs and their stability across optically induced topological interfaces, where sudden topology changes occur similarly to the early-universe theories [2].

[1] Baio, G. & Borgh M. O, arXiv:2401.04103 (2024). [2] Baio, G. et al., Phys. Rev. Research 6, 013046 (2024).

Mathematics

Audience: researchers in the topic

Fluids and Structures Seminar @ UEA