1,817,112 research outputs found
Dynamic Exponent of t-J and t-J-W Model
Drude weight of optical conductivity is calculated at zero temperature by
exact diagonalization for the two-dimensional t-J model with the two-particle
term, . For the ordinary t-J model with =0, the scaling of the Drude
weight for small doping concentration is
obtained, which indicates anomalous dynamic exponent =4 of the Mott
transition. When is switched on, the dynamic exponent recovers its
conventional value =2. This corresponds to an incoherent-to-coherent
transition associated with the switching of the two-particle transfer.Comment: LaTeX, JPSJ-style, 4 pages, 5 eps files, to appear in J. Phys. Soc.
Jpn. vol.67, No.6 (1998
Generalized - Model
By parameterizing the t-j model we present a new electron correlation model
with one free parameter for high-temperature superconductivity. This model is
of symmetry. The energy spectrums are shown to be modulated by
the free parameter in the model. The solution and symmetric structures of the
Hilbert space, as well as the Bethe ansatz approach are discussed for special
cases.Comment: 13 page, Latex, to appear in J. Phys.
Polaron in t-J model
We present numeric results for ground state and angle resolved photoemission
spectra (ARPES) for single hole in t-J model coupled to optical phonons. The
systematic-error free diagrammatic Monte Carlo is employed where the Feynman
graphs for the Matsubara Green function in imaginary time are summed up
completely with respect to phonons variables, while magnetic variables are
subjected to non-crossing approximation. We obtain that at electron-phonon
coupling constants relevant for high Tc cuprates the polaron undergoes
self-trapping crossover to strong coupling limit and theoretical ARPES
demonstrate features observed in experiment: a broad peak in the bottom of the
spectra has momentum dependence which coincides with that of hole in pure t-J
model.Comment: 4 pages, 4 figure
Single-hole properties in the - and strong-coupling models
We report numerical results for the single-hole properties in the -
model and the strong-coupling approximation to the Hubbard model in two
dimensions. Using the hopping basis with over states we discuss (for an
infinite system) the bandwidth, the leading Fourier coefficients in the
dispersion, the band masses, and the spin-spin correlations near the hole. We
compare our results with those obtained by other methods. The band minimum is
found to be at () for the - model for , and for the strong-coupling model for . The bandwidth
in both models is approximately at large , in rough agreement with
loop-expansion results but in disagreement with other results. The
strong-coupling bandwidth for t/J\agt6 can be obtained from the - model
by treating the three-site terms in first-order perturbation theory. The
dispersion along the magnetic zone face is flat, giving a large
parallel/perpendicular band mass ratio.Comment: 1 RevTeX file with epsf directives to include 8 .eps figures 8 figure
files encoded using uufile
Fidelity and superconductivity in two-dimensional t-J models
We compute the ground-state fidelity and various correlations to gauge the
competition between different orders in two-dimensional t-J-type models. Using
exact numerical diagonalization techniques, these quantities are examined for
(i) the plain t-J and t-t'-J models, (ii) for the t-J model perturbed by
infinite-range d-wave or extended-s-wave superconductivity inducing terms, and
(iii) the t-J model, plain and with a d-wave perturbation, in the presence of
non-magnetic quenched disorder. Various properties at low hole doping are
contrasted with those at low electron filling. In the clean case, our results
are consistent with previous work that concluded that the plain t-J model
supports d-wave superconductivity. As a consequence of the strong correlations
present in the low hole doping regime, we find that the magnitude of the d-wave
condensate occupation is small even in the presence of large d-wave
superconductivity inducing terms. In the dirty case, we show the robustness of
the ground state in the strongly correlated regime against disorder.Comment: 11 pages, 12 figures, as publishe
Superconductivity in the t-J model
A comparison of microscopic theories of superconductivity in the limit of
strong electron correlations is presented. We consider results for the
two-dimensional t-J model obtained within the projection technique for the
Green functions in terms of the Hubbard operators and the slave-fermion
representation for the RVB state. It is argued that the latter approach
resulting in the odd-symmetry p-wave pairing for fermions is inadequate.Comment: 11 pages, RevTex, 1 figure, to appear in Condensed Matter Physics
v.5, No.4 (2002)(Lviv, Ukraine) v.2: corrected typo
Stripes and the t-J model
We investigate the two-dimensional t-J model at a hole doping of x = 1/8 and
J/t = 0.35 with exact diagonalization. The low-energy states are uniform (not
striped). We find numerous excited states with charge density wave structures,
which may be interpreted as striped phases. Some of these are consistent with
neutron scattering data on the cuprates and nickelates.Comment: 4 pages; 4 eps figures included in text; Revte
Phase separation in t-J ladders
The phase separation boundary of isotropic t-J ladders is analyzed using
density matrix renormalization group techniques. The complete boundary to phase
separation as a function of J/t and doping is determined for a chain and for
ladders with two, three and four legs. Six-chain ladders have been analyzed at
low hole doping. We use a direct approach in which the phase separation
boundary is determined by measuring the hole density in the part of the system
which contains both electrons and holes. In addition we examine the binding
energy of multi-hole clusters. An extrapolation in the number of legs suggests
that the lowest J/t for phase separation to occur in the two dimensional t-J
model is J/t~1.Comment: 8 pages in revtex format including 13 embedded figures, one reference
adde
Exact Results of the 1D Supersymmetric t-J Model without Translational Invariance
In this work, we continue the study of the supersymmetric t-J model with
1/r^2 hopping and exchange without translational invariance. A set of Jastrow
wavefunctions are obtained for the system, with eigenenergies explicitly
calculated. The ground state of the t-J model is included in this set of
wavefunctions. The spectrum of this t-J model consists of equal-distant energy
levels which are highly degenerate.Comment: 14 pages, Late
Two-Hole and Four-Hole Bound States in a t-J Ladder at half-filling
The two-hole excitation spectrum of the t-J ladder at half-filling is studied
using linked-cluster series expansion methods. A rich spectrum of bound states
emerges, particularly at small . Their dispersion relations and coherence
lengths are computed, along with the threshold behaviour as the bound states
merge into the continuum. A class of 4-hole bound states is also studied,
leading to the conclusion that phase separation occurs for ,
in agreement with other studies.Comment: revtex
- …