Fig. 4

The effect of electrostatic gating on the electrical transport and near-field signal at 6 K. a Schematic view of the sample with a back gate. b The DC resistance, carrier density and mobility as a function of the gate voltage measured in an independent Hall-effect experiment on the same sample. c Experimental near-field amplitude and phase with respect to the reference region as a function of the position and the gate voltage. d The averaged near-field signals in the area marked by the dashed rectangles shown in c as a function of the gate voltage. e Calculation of the gate dependence of the near-field signal performed using the carrier density values and carrier mobility 20 times smaller than the DC values shown in (b). The wavelength is 10.7 μm