Effects of electron-phonon interaction on nonequilibrium transport through a single-molecule transistor

On the basis of the nonequilibrium Green's function and nonperturbative canonical transformation for the local electron-phonon interaction (EPI), the quantum transport through a single-molecule transistor (SMT) has been investigated with particular attention paid to the joint effect of the EPI and SMT-lead coupling on the spectral function and conductance. In addition to the usual EPI-induced renormalized effects (such as the redshift, sharpening, and phonon sidebands of the SMT level), owing to improved disentangling the electron-phonon system it has been found that the profile of the spectral function of the SMT electron is sensitive to lead chemical potentials, thus can readily be manipulated by tuning the bias as well as the SMT-gate voltage. As a consequence, the broken particle-hole symmetry in this system can be clearly recognized through the phonon sidebands in the spectral function. These EPI effects also manifest themselves in the nonequilibrium transport properties of the SMT, particularly at low temperature.