Fig. 2: Visualizing and quantifying the plasmonic response of individual ferroelectric domains in t-WSe2.
a The fourth harmonic of the near-field scattering amplitude, \({s}_{4}\), plotted as a function of gate-voltage \({V}_{g}\) and measured for a line trace that crosses three ferroelectric domains (see blue arrow line in Panel c). The positions of the domain wall are indicated on the top by four solid lines. b Representative results for the voltage-dependence of the scattering amplitude, \({s}_{4}({V}_{{{{{{\rm{g}}}}}}})\), probed within AB and BA domains. These two traces were extracted from data in Panel a (dashed lines). The charge neutrality points (CNP) are distinct for the AB and BA domains. In the shaded regions, graphene is heavily doped and supports propagating plasmon polaritons launched by the tip. c, d Images of the near-field scattering amplitude, \({s}_{4}\), acquired at \({V}_{g}=+ 20{\,}{V}\) and \({V}_{g}=-10{\,}{V}\), respectively. The dashed lines mark the domain boundaries. These images reveal the contrast reversal between AB/BA domains. e Carrier density mapping extracted from the near-field amplitude \({s}_{4}\) as described in the text. All the data were acquired with photon energy \({\omega=862\,{{{{{\rm{cm}}}}}}}^{-1}\) and, for Device B, with a moiré-averaged CNP of about \(-26{\,}{V}\).
