Staff directory José María Escartín Esteban

Publications

2023

• Self-sustained deformable rotating liquid He cylinders: The pure normal fluid 3He and superfluid 4He cases

  Pi, M; Ancilotto, F; Barranco, M; Butler, SL; Escartín, JM Physical Review b; 108 (5): 54524. 2023. 10.1103/PhysRevB.108.054524. IF: 3.700

  ---

2022

• Merging of superfluid helium nanodroplets with vortices

  Escartín J.M., Ancilotto F., Barranco M., Pi M. Physical Review B; 105 (2, 024511) 2022. 10.1103/PhysRevB.105.024511. IF: 4.036

  Within density functional theory, we have investigated the coalescence dynamics of two superfluid helium nanodroplets hosting vortex lines in different relative orientations, which are drawn towards each other by the Van der Waals mutual attraction. We have found a rich phenomenology depending on how the vortex lines are oriented. In particular, when a vortex and antivortex lines are present in the merging droplets, a dark soliton develops at the droplet contact region, which eventually decays into vortex rings. Reconnection events are observed between the vortex lines or rings, leading to the creation of more vortices. Our simulations show the interplay between vortex creation and reconnections, as well as the effect of the droplet surface which pins the vortex ends and, by reflecting short-wavelength excitations produced by the interactions between vortices, strongly affects the droplet final state. Additional vorticity is nucleated in the proximity of surface indentations produced in the course of the dynamics, which in turn interact with other vortices present in the droplets. These effects, obviously absent in the case of bulk liquid helium, show that the droplet surface may act as a multiplier of vortex reconnections. The analysis of the energy spectrum shows that vortex-antivortex ring annihilation, as well as vortex-antivortex reconnections, yields roton bursts of different intensity. © 2022 American Physical Society.

  View abstract

  ---

2021

• Coexistence of vortex arrays and surface capillary waves in spinning prolate superfluid He 4 nanodroplets

  Pi M., Escartín J.M., Ancilotto F., Barranco M. Physical Review B; 104 (9, 094509) 2021. 10.1103/PhysRevB.104.094509. IF: 4.036

  Within density functional theory, we have studied the interplay between vortex arrays and capillary waves in spinning prolate He4 droplets made of several thousand helium atoms. Surface capillary waves are ubiquitous in prolate superfluid He4 droplets, and depending on the size and angular momentum of the droplet, they may coexist with vortex arrays. We have found that the equilibrium configuration of small prolate droplets is vortex free, evolving towards vortex hosting as the droplet size increases. This result is in agreement with a recent experiment [O'Connell, Phys. Rev. Lett. 124, 215301 (2020)PRLTAO0031-900710.1103/PhysRevLett.124.215301] that disclosed that vortex arrays and capillary waves coexist in the equilibrium configuration of very large drops. In contrast to viscous droplets executing rigid-body rotation, the stability phase diagram of spinning He4 droplets cannot be universally described in terms of dimensionless angular momentum and angular velocity variables: Instead, the rotational properties of superfluid helium droplets display a clear dependence on the droplet size and the number of vortices they host. © 2021 American Physical Society.

  View abstract

  ---