74,513 research outputs found
Checkerboard patterns in the t-J model
Using the density matrix renormalization group, we study the possibility of
real space checkerboard patterns arising as the ground states of the t-J model.
We find that checkerboards with a commensurate (pi,pi) background are not low
energy states and can only be stabilized with large external potentials.
However, we find that striped states with charge density waves along the
stripes can form approximate checkerboard patterns. These states can be
stabilized with a very weak external field aligning and pinning the CDWs on
different stripes.Comment: 4 pages, 5 figure
Competition Between Stripes and Pairing in a t-t'-J Model
As the number of legs n of an n-leg, t-J ladder increases, density matrix
renormalization group calculations have shown that the doped state tends to be
characterized by a static array of domain walls and that pairing correlations
are suppressed. Here we present results for a t-t'-J model in which a diagonal,
single particle, next-near-neighbor hopping t' is introduced. We find that this
can suppress the formation of stripes and, for t' positive, enhance the
d_{x^2-y^2}-like pairing correlations. The effect of t' > 0 is to cause the
stripes to evaporate into pairs and for t' < 0 to evaporate into
quasi-particles. Results for n=4 and 6-leg ladders are discussed.Comment: Four pages, four encapsulated figure
Ground State Phases of the Doped 4-Leg t-J Ladder
Using density matrix renormalization group techniques, we have studied the
ground state of the 4-leg t-J ladder doped near half-filling. Depending upon
J/t and the hole doping x, three types of ground state phases are found: (1) a
phase containing d_{x^2-y^2} pairs; (2) a striped CDW domain-wall phase, and
(3) a phase separated regime. A CDW domain-wall consists of fluctuating hole
pairs and this phase has significant d_{x^2-y^2} pair field correlations.Comment: 10 pages, with 6 Postscript figure
d_{x^2-y^2} Pair Domain Walls
Using the density matrix renormalization group, we study domain wall
structures in the t-J model at a hole doping of x=1/8. We find that the domain
walls are composed of d_{x^2-y^2} pairs and that the regions between the domain
walls have antiferromagnetic correlations that are pi phase shifted across a
domain wall. At x=1/8, the hole filling corresponds to one hole per two domain
wall unit cells. When the pairs in a domain wall are pinned by an external
field, the d_{x^2-y^2} pairing response is suppressed, but when the pinning is
weakened, d_{x^2-y^2} pair-field correlations can develop.Comment: 11 pages, with 3 Postscript figure
Energetics of Domain Walls in the 2D t-J model
Using the density matrix renormalization group, we calculate the energy of a
domain wall in the 2D t-J model as a function of the linear hole density
\rho_\ell, as well as the interaction energy between walls, for J/t=0.35. Based
on these results, we conclude that the ground state always has domain walls for
dopings 0 < x < 0.3. For x < 0.125, the system has (1,0) domain walls with
\rho_\ell ~ 0.5, while for 0.125 < x < 0.17, the system has a possibly
phase-separated mixture of walls with \rho_\ell ~ 0.5 and \rho_\ell =1. For x >
0.17, there are only walls with \rho_\ell =1. For \rho_\ell = 1, diagonal (1,1)
domain walls have very nearly the same energy as (1,0) domain walls.Comment: Several minor changes. Four pages, four encapsulated figure
Comment on ``Stripes and the t-J Model''
This is a comment being submitted to Physical Review Letters on a recent
letter by Hellberg and Manousakis on stripes in the t-J model.Comment: One reference correcte
Effect of the W-term for a t-U-W Hubbard ladder
Antiferromagnetic and d_{x2-y2}-pairing correlations appear delicately
balanced in the 2D Hubbard model. Whether doping can tip the balance to pairing
is unclear and models with additional interaction terms have been studied. In
one of these, the square of a local hopping kinetic energy H_W was found to
favor pairing. However, such a term can be separated into a number of simpler
processes and one would like to know which of these terms are responsible for
enhancing the pairing. Here we analyze these processes for a 2-leg Hubbard
ladder
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