Extended Data Fig. 1: Operating gate-voltage range of the sensor.
a,b, Gate dependence of the reflectance contrast spectrum of the device with the sensor at E = 6 mV/nm (a) and – 55 mV/nm (b). The gate voltage Vtot (= Vtg + Vbg) is proportional to the total charge density in the moiré bilayer and the sensor layer. The red and blue dashed lines mark the limits of gate voltage beyond which the sensor becomes doped, as evidenced by the emergence of the polarons (1.7–1.75 eV) and disappearance of the 2 s state (~ 1.85 eV). c, Operating range of the gate voltage (shaded area). It is primarily determined by the back gate voltage (-2 V, 4 V). The sensor is closer to the back gate. The blue and red symbols are determined from the boundaries in a, b and similar measurements at other electric fields.
