Vibron-polaron critical localization in a finite size molecular nanowire

Cyril Falvo

Laboratoire de Physique moleculaire, Univeriste de Franche-Comte, Besancon, France

Information transfer and storage constitute one of the challenges of the modern technology. In this context, surface science, which allows the adsorption of well defined nanostructures, is expected to play a key role. Although most of the studies consider the electron transport, the recent experiments of W. Ho [1] suggest an alternative based on the use of vibrational excitons, i.e. vibrons [2]. In a nano-wire, the vibrons do not propagate freely but interact with their surrounding formed by the low frequency modes of the adsorbates and by the phonons of the substrate. This non-linear coupling is responsible for the formation of small vibron polarons. The present work is devoted to the dynamics of a vibron-polaron in a finite size molecular nano-wire [3]. It is shown that the finite size of the lattice modifies the nature of the phonons and induces a modifiaction of the well-known dressing effect. The vibron-phonon interaction is thus singular at the sides of the nano-wire and generates a shift of the internal frequency of the side molecules. Depending on both the temperature and the coupling strengh, theses defects generate localized states. The occurrence of such localized states is closely related to a critical transition and is studied within the Renormalization Group Theory.


[1] L. J. Lauhon and W. Ho, Surf. Sci. 451, 219 (2000).
[2] V. Pouthier, J.C. Light and C. Girardet, J. Chem. Phys. 114, 4955 (2001).
[3] C. Falvo and V. Pouthier, J. Chem. Phys. (submitted).