Speaker
Description
Surface plasmon polaritons enable the confinement and manipulation of electromagnetic radiation far below the diffraction limit and constitute a key platform for nanoscale photonics. In conventional plasmonic systems, however, nanofocusing on tapered metallic structures is strongly constrained by the plasmonic dispersion. In particular, for conical metallic tips typically only a single mode can propagate towards the apex, limiting the control of additional photonic degrees of freedom such as orbital angular momentum. Here we investigate theoretically the propagation of surface plasmon polaritons on a conical tip made of a magnetic Weyl semimetal. The nontrivial topological band structure of Weyl semimetals, characterised by the presence of Weyl nodes, gives rise to a modified electromagnetic response that alters the propagation of plasmonic modes. As a consequence, all modes with a given sign of orbital angular momentum can propagate towards the tip apex and be nanofocused. These results reveal a mechanism for angular-momentum-selective plasmonic nanofocusing and highlight the potential of topological materials for manipulating structured light at the nanoscale.