arXiv subjects

F. Mila

Publications and source records attributed to F. Mila.

93 records · Page 6Linked to original sources

arXiv1996

Confinement and transverse conductivity in coupled Luttinger liquids

One--particle interchain hopping in a system of coupled Luttinger liquids is investigated by use of exact diagonalizations techniques. Firstly, the two chains problem of spinless fermions is studied in order to see the behaviour of the band splitting as a function of the exponent $α$ which characterizes the $1D$ Luttinger liquid. Moderate intra-chain interactions can lead to a strong reduction of this splitting. The on-set of the confinement within the individual chains (defined by a vanishing splitting) seems to be governed by $α$. We give numerical evidence that inter-chain coherent hopping can be totally suppressed for $α\sim 0.4$ or even smaller $α$ values. The transverse conductivty is shown to exhibit a strong incoherent part. Even when coherent inter-chain hopping is believed to occur (at small $α$ values), it is shown that the coherent Drude weight is always significantly smaller than the incoherent weight. Implications for the optical experiments in quasi-1D organic or high-$T_c$ superconductors is outlined.

cond-mat↗

arXiv1996

One particle interchain hopping in coupled Hubbard chains

Interchain hopping in systems of coupled chains of correlated electrons is investigated by exact diagonalizations and Quantum-Monte-Carlo methods. For two weakly coupled Hubbard chains at commensurate densities (e.g. n=1/3) the splitting at the Fermi level between bonding and antibonding bands is strongly reduced (but not suppressed) by repulsive interactions extending to a few lattice spacings. The magnitude of this reduction is directly connected to the exponent $α$ of the 1D Luttinger liquid. However, we show that the incoherent part of the single particle spectral function is much less affected by the interchain coupling. This suggests that incoherent interchain hopping could occur for intermediate $α$ values.

cond-mat↗

arXiv1994

Charge gap in the one--dimensional dimerized Hubbard model at quarter-filling

We propose a quantitative estimate of the charge gap that opens in the one-dimensional dimerized Hubbard model at quarter-filling due to dimerization, which makes the system effectively half--filled, and to repulsion, which induces umklapp scattering processes. Our estimate is expected to be valid for any value of the repulsion and of the parameter describing the dimerization. It is based on analytical results obtained in various limits (weak coupling, strong coupling, large dimerization) and on numerical results obtained by exact diagonalization of small clusters. We consider two models of dimerization: alternating hopping integrals and alternating on--site energies. The former should be appropriate for the Bechgaard salts, the latter for compounds where the stacks are made of alternating $TMTSF$ and $TMTTF$ molecules. % $(TMTSF)_2 X$ and $(TMTTF)_2 X$ ($X$ denotes $ClO_4$, $PF_6$, $Br$...).

cond-mat↗