Fig. 4: Gate-specific ferroelectricity controlled by the other gate.

a Two regimes are identified according to the stability of the hysteretic behavior. Below the threshold of V_b/d_b ~0.15 V nm⁻¹ the ferroelectricity is stable (highlighted in blue), whereas it becomes more and more fragile when exceeding the threshold. The scanning ranges used in other panels and Fig. S6 are denoted. b Take the scanning range of V_b/d_b as above 0.2 V nm⁻¹, one obtains a phase diagram without ferroelectric hysteresis by scanning V_t/d_t slowly (see its hysteresis-free counterpart in Fig. S3). However, the anomalous screening remains robust. c The relaxation to the stable states shown in b is quantified by a temporal characterization. Two representative points are selected: one is for V_t > 0 in the backward scan and the other is V_t < 0 in the forward scan. The characteristic time fitted by an exponential decay function are 7.1 and 0.2 h, respectively. Measurement details and raw data can be found in Fig. S4.d Below the threshold, a regular parallelogram can be formed. An obvious criterion is that the resistance ridge at CNP in the anomalous screening regime is strictly parallel with the y axis. Here the scanning range of V_b/d_b is 0.1 (left) and 0.15 (right) V nm⁻¹. The label ON/OFF means hysteresis loops are switched on/off. e In a larger scanning range of V_b ~0.21 V nm⁻¹, the relaxation distorts the parallelogram in the upper-left corner of the V_t-V_b phase diagram, i.e., the ridge is no more in parallel with the y axis; furthermore, it eliminates completely the hysteresis in the lower-right corner. f By increasing the scanning rate through a particular scheme (see details in Fig. S5), the relaxation could be overcome and hence a full hysteresis loop is restored.