Extended Data Fig. 2: Charge neutrality of the sensor.
a. Conduction band alignment for the TMD layers involved in the device structure under zero external electric field. b-d, First energy derivative of the sensor reflection contrast spectrum \((\frac{dR}{d{\epsilon }})\) as a function of the total filling factor. The gate voltages are scanned along the three arrowed lines in Fig. 1b with \({\nu }_{m} > 0\) and \({\nu }_{t}=0\) (b), \({\nu }_{m}=0\) and \({\nu }_{t} > 0\) (c) and \({\nu }_{m}=1\) and \({\nu }_{t} > 0\) (d). Incompressible states are labeled by their filling factors. The 1 s and 2 s excitons of the WSe2 sensor layer as well as the 2 s exciton of the MoSe2 target layer are labeled. The robust 1 s exciton resonance of the WSe2 layer, irrespective of the filling factor, demonstrates the charge neutrality of the sensor.
