52,102 research outputs found
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
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.
Doping-driven transition to a time-reversal breaking state in the phase diagram of the cuprates
Motivated by recent tunnelling and Andreev-reflection experiments, we study
the conditions for a quantum transition within the superconducting phase of the
cuprates,in which a bulk imaginary (time-reversal breaking) component
appears in addition to the order parameter.
We examine in detail the role of some important physical features of the
cuprates.In particular we show that a closed Fermi surface,a bilayer splitting,
an orthorhombic distortion,and the proximity to a quantum critical point around
optimal doping favor the appearance of the imaginary component. These findings
could explain why the mixed order parameter is
observed in YBCO and LSCO, and suggest that it could appear also in Bi2212. We
also predict that, in all cuprates, the mixed state should be stable only in a
limited doping region all contained beneath the dome. The
behavior of the specific heat at the secondary transition is discussed.Comment: 8 pages, 3 figures. Expanded text, 1 extra figur
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