Asymmetric current-voltage curve

In the early 1950 s it first became possible to determine the photoelectric sensitivity of dyes of different classes (phthalocyanines, cyanines, etc.) by measuring barrier-layer photopotentials in cases where barriers were strongly affected by carriers trapped in the surface states of adsorbed gases 54-56>. Jn agreement with the theory of inorganic surface-barrier rectifiers, asymmetric current-voltage curves were also observed. 

The first concrete proposal for UE was the 1974 Ansatz by Ari Aviram and Mark A. Ratner that a rectifier of electrical current could be achieved with a single molec-ule. A rectifier is an electronic device through which electrical current is conducted asymmetrically, i.e., preferentially from left to right, rather than vice versa the IV curve is asymmetrical with voltage. 

Further, we studied the nonequilibrium current for large bias-voltages (Fig. 26). Because e iCoulomb interaction, the I-V curve is asymmetric for Vbias> and there are one step and one maximum for the current. The step contributes to one peak for the conductance. When we introduce the Coulomb interaction to the... 

Fig. 34 Vibronic instability in an asymmetric multilevel model voltage-current curve, differential conductance, and the number of excited vibrons (crosses). Dashed line show the voltage-current curve without vibrons (details see in the text).

The voltage-current curve is now asymmetric, a large step corresponds to the resonant level with inverted population. 

As you can see, the LTSpice simulation plots the DC current dependency correctly, but the influence of the AC amplitude is distorted. The AC amplitude has a strong influence on the results, which is to be expected according to the theory [8, 9]. The measured curve with 1 A AC amplitude deviates more from the Simulation with 1 A and the curve with 10 mV amplitude is closer to the simulation, for the case without any superposed DC current. This means a better linearity is achieved by continuously adjusting the current amplitude so a maximal voltage response of 10 mV is met. The asymmetric behavior is clearly visible when comparing the curves with the superposed charging and discharging DC currents. In both cases, the measured impedance is smaller than the impedance without any superposed DC current. 

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