Measuring the phonon-assisted spectral function by using a nonequilibrium three-terminal single-molecular device

The electron transport through a three-terminal single-molecular transistor (SMT) is theoretically studied. We find that the differential conductance of the third and weakly coupled terminal versus its voltage matches well with the spectral function versus the energy when certain conditions are met. Particularly, this excellent matching is maintained even for the complicated structure of the phonon-assisted side peaks. Thus, this device offers an experimental approach to explore the shape of the phonon-assisted spectral function in detail. In addition, we discuss the conditions of a perfect matching. The results show that at low temperatures, the matching survives regardless of the bias and the energy levels of the SMT. However, at high temperatures, the matching is destroyed.