Bias dependence of the interlayer conductance in moire tunnel junctions

We have investigated the bias effect in moire tunnel junctions using an extending theory developed previously by us. The theory is founded on optical methods, and thus, compared to the conventional theories, it can better take into account the superposition of periods and the corresponding coherence in moire tunnel junctions. Here, the bias effect on the interlayer conductance is studied under two cases: (1) The thickness of the upper layer is much less that of the lower layer. (2) The thickness of the upper layer is equal to that of the lower layer. In the former case, the bias can significantly depress the intensity of the peak. Physically, the attenuation of the intensity of the peak originates from the breaking of the periodicity of the potential by the bias. In the latter case, the intensity of the peak is less attenuated by the bias, while the position of the peak shifts to smaller angle. These phenomena are due to the significant alteration of the wave vectors at the interface caused by the bias. In addition, we have investigated the influences of barrier thickness on the interlayer conductance in the latter case. It is found that, with increasing barrier thickness, the intensity of the peak will decrease significantly, and be depressed by the bias more significantly. Finally, we discuss how to design the device to decrease the negative impact of the bias on the performance and how to utilize the bias to tune the parameters of the device.