Plasmonic Twistronics: Discovery of Plasmonic Skyrmion Bags

SPICE Workshop on Spin textures: Magnetism meets Plasmonics, July 23rd - 25th 2024

Harald Giessen

  1. Giessen1, J. Schwab1, A. Neuhaus², P. Dreher², S. Tsesses3, A. Mantha1, F. Mangold1, B. Frank1, G. Bartal3, F.-J. Meyer zu Heringdorf2, and T. J. Davis1,2,4 
  2. 4th Physics Institute, Research Center SCoPE, and Integrated Quantum Science and Technology Center, University of Stuttgart, Germany
  3. Faculty of Physics and Center for Nanointegration, University of Duisburg-Essen, Germany
  4. Andrew and Erna Viterbi Department of Electrical Engineering, Technion-Israel Institute of Technology, Israel
  5. School of Physics, University of Melbourne, Australia

 

Plasmonic skyrmion lattices are created by the interference of surface plasmon polariton waves. Superimposing two plasmonic skyrmion lattices with a relative twist creates a moiré skyrmion superlattice. Their vector fields are calculated numerically and measured using time-resolved PEEM vector microscopy, demonstrating that the topology contains skyrmion bags of controllable size for certain magic angles.

Twistronics are studied intensively in 2D-materials, especially in twisted bilayer graphene, following the discovery of flat electronic bands. This has led to groundbreaking findings, such as unconventional superconductivity and correlated insulator states. In these systems, the moiré lattice is created by introducing a relative twist between the upper and lower layer of the material by a twist angle .

Here, we explore the application of twistronics in plasmonic systems by superimposing two plasmonic skyrmion lattices to create a moiré skyrmion superlattice. Skyrmions are topological excitations in continuous vector fields observed in magnetic materials and liquid crystals, but they can also be created in plasmonic systems through interference of surface plasmon polariton waves [1, 2].

We combine the concepts of twistronics with plasmonic topological excitations and demonstrate that the topology of moiré skyrmion lattices contains skyrmion bags as complex topological quasiparticles that so far have been demonstrated only in liquid crystals, and whose formation has been predicted in chiral ferromagnets [3]. The size of plasmonic skyrmion bags can be controlled by the twist angle and its center of rotation. The resulting electric field distribution of a skyrmion bag can be derived numerically (see Figure 1 (b)) and verified experimentally using time-resolved two-photon photoemission electron microscopy (PEEM) vector microscopy [2].

The ability to control topological properties of light has great potential for applications such as spin-optics, imaging, structured illumination microscopy, non-dipolar light-matter-interaction, as well as topological and quantum technologies.

References

[1] S. Tsesses, E. Ostrovsky, K. Cohen, B. Gjonaj, N. H. Lindner, G. Bartal, Optical skyrmion lattice in evanescent electromagnetic fields. Science, 361, 993–996 (2018).

[2] T. J. Davis, D. Janoschka, P. Dreher, B. Frank, F. J. Meyer zu Heringdorf, H. Giessen, Ultrafast vector imaging of plasmonic skyrmion dynamics with deep subwavelength resolution. Science, 368, eaba6415 (2020).

[3] D. Foster, C. Kind, P. J. Ackerman, J. S. B. Tai, M. R. Dennis, I. I. Smalyukh, Two-dimensional skyrmion bags in liquid crystals and ferromagnets. Nat Phys. 15, 655–659 (2019).