Transport through double quantum dot with electron-LO-phonon interaction

We theoretically study the transport through a serial double quantum dot (DQD) in the presence of electron-LO-phonon interaction. In contrast to the case of acoustic phonon,\footnote{P.\ Roulleau {\it et al}., Nat.\ Commun.\ {\bf 2}, 239 (2011).} the coherent coupling between an electron and an optical phonon, so-called polaron formation, has a small dissipation, which influences the transport properties markedly. We calculate the current through the DQD using the Keldysh Green function, as a function of the tuning of energy levels between the quantum dots, when the bias voltage is sufficiently large. The electron-phonon interaction is considered by the perturbation expansion. We find a subpeak structure of the current due to the polaron formation and evaluate elastic and inelastic components of the current.