where PFE(t) is the time-dependent FE polarization density, C is the parallel plate capacitance density, A is the area, and IR is the DC current of the ferroelectric. The three terms in Eq. (1) are the FE, capacitive, and DC resistive responses, respectively. IR is dominant by the tunneling current in FTJ and responsible for the TER effect. The FE and capacitive responses are time-dependent but could be substantial especially when IR is small and the voltage ramp rate is fast.The trajectory of P-V loop is described using the multi-domain Preisach theory [14] that is well calibrated with the experimental saturation and minor P-V hysteresis loops (Fig.7).The potential profile within the stack is then solved using the Poisson equation, and the WKB equation is used for calculating the tunneling current. Additional nonpolar ILs mayexist between FE and electrodes and thus are considered in both electrostatic and tunneling current calculation. Table I shows the complete flow for solving I(t) including not onlytunneling but also FE and capacitive components and lists all detailed equations used in our model.