Coupled pair of one- and two-dimensional magnetoplasmons on electrons on helium

Electrons on the liquid helium surface form an extremely clean two dimensional system where different plasmon-excitations can coexist. Under a magnetic field time reversal symmetry is broken and all bulk magneto-plasmons become gaped at frequencies below cyclotron resonance while chiral one edge appear perimeter. We theoretically show that presence of homogeneous density gradient in electron gas leads to formation delocalized magneto-plasmon mode same frequency range as lowest edge-magnetoplasmon mode. experimentally confirm its existence by measuring corresponding peak dependence admittance gas. This allows realize prototype investigate coupling between one-dimensional single Such model be important for understanding transport properties topological materials states dimensionality