  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 a 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 red-shift, sharpening,
and phonon-sidebands of the SMT level), owing to improved disentagling 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.
