404 research outputs found
Reply to the Comment by Sandvik, Sengupta, and Campbell on ``Ground State Phase Diagram of a Half-Filled One-Dimensional Extended Hubbard Model''
In their Comment (see cond-mat/0301237), Sandvik, Sengupta, and Campbell
present some numerical evidences to support the existence of an extended
bond-order-wave (BOW) phase at couplings (U,V) weaker than a tricritical point
(U_t,V_t) in the ground state phase diagram of the one-dimensional half-filled
U-V Hubbard model. They claim that their results do not agree with the phase
diagram proposed in my Letter (cond-mat/0204244), which shows a BOW phase for
couplings stronger than the critical point only. However, I argue here that
their results are not conclusive and do not refute the phase diagram described
in the Letter.Comment: 1 page, published versio
Optical conductivity of the one-dimensional dimerized Hubbard model at quarter filling
We investigate the optical conductivity in the Mott insulating phase of the
one-dimensional extended Hubbard model with alternating hopping terms
(dimerization) at quarter band filling. Optical spectra are calculated for the
various parameter regimes using the dynamical density-matrix renormalization
group method. The study of limiting cases allows us to explain the various
structures found numerically in the optical conductivity of this model. Our
calculations show that the dimerization and the nearest-neighbor repulsion
determine the main features of the spectrum. The on-site repulsion plays only a
secondary role. We discuss the consequences of our results for the theory of
the optical conductivity in the Bechgaard salts.Comment: 11 pages and 12 figure
Correlations and confinement of excitations in an asymmetric Hubbard ladder
Correlation functions and low-energy excitations are investigated in the
asymmetric two-leg ladder consisting of a Hubbard chain and a noninteracting
tight-binding (Fermi) chain using the density matrix renormalization group
method. The behavior of charge, spin and pairing correlations is discussed for
the four phases found at half filling, namely, Luttinger liquid, Kondo-Mott
insulator, spin-gapped Mott insulator and correlated band insulator.
Quasi-long-range antiferromagnetic spin correlations are found in the Hubbard
leg in the Luttinger liquid phase only. Pair-density-wave correlations are
studied to understand the structure of bound pairs found in the Fermi leg of
the spin-gapped Mott phase at half filling and at light doping but we find no
enhanced pairing correlations. Low-energy excitations cause variations of spin
and charge densities on both legs that demonstrate the confinement of the
lowest charge excitations on the Fermi leg while the lowest spin excitations
are localized on the Hubbard leg in the three insulating phases. The velocities
of charge, spin, and single-particle excitations are investigated to clarify
the confinement of elementary excitations in the Luttinger liquid phase. The
observed spatial separation of elementary spin and charge excitations could
facilitate the coexistence of different (quasi-)long-range orders in
higher-dimensional extensions of the asymmetric Hubbard ladder
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