Electron-phonon coupling close to a metal-insulator transition in one dimension

We consider a one-dimensional system of electrons interacting via a short-range repulsion and coupled to phonons close to the metal-insulator transition at half filling. We argue that the metal-insulator transition can be described as a standard one dimensional incommensurate to commensurate transition, even if the electronic system is coupled to the lattice distortion. By making use of known results for this transition, we prove that low-momentum phonons do not play any relevant role close to half-filling, unless their coupling to the electrons is large in comparison with the other energy scales present in the problem. In other words the effective strength of the low-momentum transferred electron-phonon coupling does not increase close to the metal-insulator transition, even though the effective velocity of the mobile carriers is strongly diminished.Comment: 20 pages, REVTEX styl

Collective transport and optical absorption near the stripe criticality

Within the stripe quantum critical point scenario for high $T_c$ superconductors, we point out the possible direct contribution of charge collective fluctuations to the optical absorption and to the d.c. resistivity.Comment: 2 pages 2 figures 1 style fil

Single-particle spectra near a stripe instability

We analyze the single-particle spectra of a bi-layered electron system near a stripe instability and compare the results with ARPES experiments on the Bi2212 cuprate superconductor near optimum doping, addressing also the issue of the puzzling absence of bonding-antibonding splitting.Comment: Proceedings of the XXII International Conference on Low Temperature Physics August 4-11, 1999, Espoo and Helsinki, Finland (minor changes to the figure) Similar results in the Proceedings of the International Workshop on ``Electronic crystals, ECRYS-99'', May 31-June 5 1999, La Colle sur Loup (France), J. Phys. IV France 9, Pr10-337 (1999

Phase Separation close to the density-driven Mott transition in the Hubbard-Holstein model

The density driven Mott transition is studied by means of Dynamical Mean-Field Theory in the Hubbard-Holstein model, where the Hubbard term leading to the Mott transition is supplemented by an electron-phonon (e-ph) term. We show that an intermediate e-ph coupling leads to a first-order transition at T=0, which is accompanied by phase separation between a metal and an insulator. The compressibility in the metallic phase is substantially enhanced. At quite larger values of the coupling a polaronic phase emerges coexisting with a non-polaronic metal.Comment: 4 pages, 3 figures. Slightly revised text. More details in Fig.1 and 2. Smaller size version of Fig.