Laterally screened two-dimensional plasma excitations in a disk-shaped two-dimensional electron system

We investigated plasma excitations in a disk-shaped two-dimensional electron system (2DES) laterally screened by a coplanar metal electrode surrounding the 2DES with a fixed-size separation gap around the perimeter of the disk. We find that lateral screening leads to a significant redshift in the plasmon frequency as the gap width approaches zero. It is caused by the redistribution of charges in the metallic gate that induce a logarithmic screening potential in the 2DES region. The spectroscopy of laterally screened plasmons provides valuable information on the structure of the 2DES edge. We developed a theoretical model and performed numerical simulations which show good agreement with the experimental data.