203 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
Charge-density-wave formation in the Edwards fermion-boson model at one-third band filling
We examine the ground-state properties of the one-dimensional Edwards
spinless fermion transport model by means of large-scale density-matrix
renormalization-group calculations. Determining the single-particle gap and the
Tomonaga-Luttinger liquid parameter () at zero temperature, we prove
the existence of a metal-to-insulator quantum phase transition at one-third
band filling. The insulator---established by strong correlation in the
background medium---typifies a charge density wave (CDW) that is commensurate
with the band filling. is very small at the quantum critical
point, and becomes in the infinitesimally doped
three-period CDW, as predicted by the bosonization approach.Comment: 6 pages, 3 figures, contributions to SCES 201
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
Local density of states of the one-dimensional spinless fermion model
We investigate the local density of states of the one-dimensional half-filled
spinless fermion model with nearest-neighbor hopping t>0 and interaction V in
its Luttinger liquid phase -2t < V <= 2t. The bulk density of states and the
local density of states in open chains are calculated over the full band width
4t with an energy resolution <= 0.08t using the dynamical density-matrix
renormalization group (DDMRG) method. We also perform DDMRG simulations with a
resolution of 0.01t around the Fermi energy to reveal the power-law behaviour
predicted by the Luttinger liquid theory for bulk and boundary density of
states. The exponents are determined using a finite-size scaling analysis of
DDMRG data for lattices with up to 3200 sites. The results agree with the exact
exponents given by the Luttinger liquid theory combined with the Bethe Ansatz
solution. The crossover from boundary to bulk density of states is analyzed. We
have found that boundary effects can be seen in the local density of states at
all energies even far away from the chain edges
Parallelization Strategies for Density Matrix Renormalization Group Algorithms on Shared-Memory Systems
Shared-memory parallelization (SMP) strategies for density matrix
renormalization group (DMRG) algorithms enable the treatment of complex systems
in solid state physics. We present two different approaches by which
parallelization of the standard DMRG algorithm can be accomplished in an
efficient way. The methods are illustrated with DMRG calculations of the
two-dimensional Hubbard model and the one-dimensional Holstein-Hubbard model on
contemporary SMP architectures. The parallelized code shows good scalability up
to at least eight processors and allows us to solve problems which exceed the
capability of sequential DMRG calculations.Comment: 18 pages, 9 figure
Spectral function of the one-dimensional Hubbard model away from half filling
We calculate the photoemission spectral function of the one-dimensional
Hubbard model away from half filling using the dynamical density matrix
renormalization group method. An approach for calculating momentum-dependent
quantities in finite open chains is presented. Comparison with exact Bethe
Ansatz results demonstrates the unprecedented accuracy of our method. Our
results show that the photoemission spectrum of the quasi-one-dimensional
conductor TTF-TCNQ provides evidence for spin-charge separation on the scale of
the conduction band width.Comment: REVTEX, 4 pages including 4 EPS figures (changed); correct chemical
potential used to define excitation energies in figures and tex
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