Edge diffraction and plasmon launching in two-dimensional electron systems

Abstract

Diffraction of light at lateral inhomogenities is a central process in the near-field studies of nanoscale phenomena, especially the propagation of surface waves. Theoretical description of this process is extremely challenging due to breakdown of plane-wave methods. Here, we present and analyze an exact solution for electromagnetic wave diffraction at the linear junction between twodimensional electron systems (2DES) with dissimilar surface conductivities. The field at the junction is a combination of three components with different spatial structure: free-field component, nonresonant edge component, and surface plasmon-polariton (SPP). We find closed-form expressions for efficiency of photon-to-plasmon conversion by the edge being the ratio of electric fields in SPP and incident wave. Particularly, the conversion efficiency can considerably exceed unity for the contact between metal and 2DES with large impedance. Our findings can be considered as a first step toward quantitative near-field microscopy of inhomogeneous systems and polaritonic interferometry.

Plasmonic modes at inclined edges of anisotropic 2D materials

“…Spatial profiles of electric field and charge density oscillations corresponding to the edge mode can be naturally divided into two parts (the similar field decomposition was noted in Ref. [81]). The first part is always strongly confined to the edge, and the second part corresponds to evanescent 2D waves with complex wave vector projections perpendicular to the edge.…”