L. G. Caron

RENORMALIZATION GROUP APPROACH TO QUASI-ONE-DIMENSIONAL CONDUCTORS

We review the recent progress made in the application of the renormalization group method to the interacting quasi-one-dimensional electron gas. From the functional integral formulation of the partition function as expressed in terms of anticommuting Grassmann variables, the effects of single-electron interchain hopping on the mechanisms of propagation of correlations leading to long range ordering is analyzed in full details for the non-half-filled band case. Within a unified formalism, the scaling features of the purely one-dimensional correlations, the dimensionality crossover of both single and composite particles, the critical temperatures, and the responses functions are described.

New Mechanisms for Phase Transitions in Quasi-One-Dimensional Conductors

We show that interchain single-particle tunnelling in quasi-one-dimensional solids invariably leads to effective interchain pair tunnelling interactions even when there is no gap in the intrachain excitation spectrum. These can lead to antiferromagnetism well before the dimensionality crossover or to superconductivity below this crossover whenever the nesting conditions of the Fermi surface are poor. We thus suggest a new mechanism for super-conductivity which would involve Cooper pairs on different chains and an isotropic gap compatible with recent nuclear-relaxation rate experiments.

Transmission of 0–15 eV monoenergetic electrons through aliphatic and alicyclic hydrocarbon films

High‐resolution electron transmission spectra and their second energy derivatives were measured in thin (∼100 A) organic films deposited on polycrystalline and single crystal metal substrates. For all compounds investigated (i.e., benzene, pentene, hexane, 1‐hexane, trans‐2, trans‐4‐hexadiene, 1,3,5‐hexatriene, norbornene, norbornadiene, 1,3‐cycloheptadiene, and 1,3,5‐cycloheptatriene), these spectra contained broad maxima observable in dc curves and much sharper and less intense features, that were usually only visible in the doubly differentiated spectra (DDTS). The broad maxima were interpreted to result from a convolution of inelastically scattered electron currents that increased the total transmitted current, mainly due to a change in their reflection coefficient at the film‐vacuum interface. The sharper features were more difficult to interpret. In hexatriene, norbormadiene, and heptatriene, they could be correlated with gas phase electronic transitions. As previously observed in C6‐alicyclic hydro...

Superconductivity in armchair carbon nanotubes

We use the momentum space renormalization group to study the influence of phonons and the Coulomb interaction on the superconducting response function of armchair single-walled nanotubes. We do not find superconductivity in undoped single nanotubes. When doped, superconducting fluctuations can develop because of the phonons but remain small and are easily destroyed by the Coulomb interaction. The origin of superconductivity in ropes of nanotobes is most likely an intertube effect. Projections to zigzag nanotubes indicate a more favorable disposition to superconducting fluctuations.

Density matrix renormalization group applied to the ground state of the XY spin-Peierls system.

We use the density matrix renormalization group (DMRG) to map out the ground state of a XY-spin chain coupled to dispersionless phonons of frequency

GROUND-STATE PROPERTIES OF THE ONE-DIMENSIONAL KONDO LATTICE AT PARTIAL BAND FILLING

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Temperature and thickness dependence of the 0–15 eV electron transmission spectra of rare gas films

. We confirm the existence of a critical spin-phonon coupling

Thermodynamic Density Matrix Renormalization Group Study of the Magnetic Susceptibility of Half-Integer Quantum Spin Chains

% \alpha _c\propto \omega ^{0.7}

Evolution of the spin-Peierls transition in the (TMTTF)2X salts (X=AsF6,PF6,Br) under pressure

for the onset of the spin gap bearing the signature of a Kosterlitz-Thouless transition. We also observe a classical-quantum crossover when the spin-Peierls gap

Importance of one-dimensional correlations in the phase diagram of the (TMTTF)2-(TMTSF)2-X salts

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