93 research outputs found
Violation of Luttinger's Theorem in the Two-Dimensional t-J Model
We have calculated the high temperature series for the momentum distribution
function n_k of the 2D t-J model to 12th order in inverse temperature. By
extrapolating the series to T=0.2J we searched for a Fermi surface of the 2D
t-J model. We find that three criteria used for estimating the location of a
Fermi surface violate Luttinger's Theorem, implying the 2D t-J model does not
have an adiabatic connection to a non-interacting model.Comment: 4 pages, 5 figures. Version with grayscale figures available upon
reques
Theory of Electron Spin Relaxation in n-Doped Quantum Wells
Recent experiments have demonstrated long spin lifetimes in uniformly n-doped
quantum wells. The spin dynamics of exciton, localized, and conduction spins
are important for understanding these systems. We explain experimental behavior
by invoking spin exchange between all spin species. By doing so we explain
quantitatively and qualitatively the striking and unusual temperature
dependence in (110)-GaAs quantum wells. We discuss possible future experiments
to resolve the pertinent localized spin relaxation mechanisms. In addition, our
analysis allows us to propose possible experimental scenarios that will
optimize spin relaxation times in GaAs and CdTe quantum wells.Comment: Small corrections made. Accepted to Phys. Rev. B. 8 pages, 5 figure
Limits on Phase Separation for Two-Dimensional Strongly Correlated Electrons
From calculations of the high temperature series for the free energy of the
two-dimensional t-J model we construct series for ratios of the free energy per
hole. The ratios can be extrapolated very accurately to low temperatures and
used to investigate phase separation. Our results confirm that phase separation
occurs only for J/t greater than 1.2. Also, the phase transition into the phase
separated state has Tc of approximately 0.25J for large J/t.Comment: 4 pages, 6 figure
Field-induced local moments around nonmagnetic impurities in metallic cuprates
We consider a defect in a strongly correlated host metal and discuss, within
a slave boson mean field formalism for the model, the formation of an
induced paramagnetic moment which is extended over nearby sites. We study in
particular an impurity in a metallic band, suitable for modelling the optimally
doped cuprates, in a regime where the impurity moment is paramagnetic. The form
of the local susceptibility as a function of temperature and doping is found to
agree well with recent NMR experiments, without including screening processes
leading to the Kondo effect.Comment: 7 pages, submitted to Phys Rev
Hole-hole correlations in the limit of the Hubbard model and the stability of the Nagaoka state
We use exact diagonalisation in order to study the infinite - limit of
the two dimensional Hubbard model. As well as looking at single-particle
correlations, such as , we also study {\it N-particle correlation
functions} which compare the relative positions of {\it all} the particles in
different models. In particular we study 16 and 18-site clusters and compare
the charge correlations in the Hubbard model with those of spinless fermions
and hard-core bosons. We find that although low densities of holes favour a
`locally-ferromagnetic' fermionic description, the correlations at larger
densities resemble those of pure hard-core bosons surprisingly well .Comment: 15 pages, REVTE
Comment on "T-dependence of the magnetic penetration depth in unconventional superconductors at low temperatures: Can it be linear?"
We show that the clean superconductor with line of gap nodes is not in
conflict with the Nernst theorem. The answer to the question in the title of
the Schopohl-Dolgov paper in Phys. Rev. Lett. 80 (1998) 4761 (cond-mat/9802264)
is yes.Comment: Comment to the paper by Schopohl and Dolgov in Phys. Rev. Lett. 80
(1998) 4761 (cond-mat/9802264), RevTex file, 1 page, no figures, typos are
corrected, submitted to Phys. Rev. Let
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