147,064 research outputs found
Holon Pairing Instability based on the Bethe-Salpeter Equation obtained from the t-J Hamiltonians of both U(1) and SU(2) Slave-boson Symmetries
We investigate a possibility of holon pairing for bose condensation based on
the
Bethe-Salpeter equation obtained from the use of the t-J Hamiltonians of both
t he U(1) and SU(2) slave-boson symmetries. It is shown that the vertex
function contributed from ladder diagram series involving holon-holon
scattering channel in the Bethe-Salpeter equation leads to a singular behavior
at a critical temperature at each hole doping concentration, showing the
instability of the normal state against holon pairing. We find that the holon
pairing instability occurs only in a limited range of hole doping, by showing
an "arch" shaped bose condensation line in agreement with observation for high
cuprates. It is revealed that this is in agreement with a functional
integral approach of the slave-boson theories.Comment: 4 pages, 5 figure
Universal scaling behavior of pseudogap with doping in high Tc cuprates; temperature and doping dependence of spectral intensity
Based on our improved SU(2) slave-boson approach (Phys. Rev. B 64,
052501(2001)) to the t-J Hamiltonian, we report a scaling behavior of pseudogap
with doping and the temperature and doping dependence of spectral functions. In
addition we discuss the cause of hump and quasi-particle peak in the observed
spectral functions of high Tc cuprates. It is demonstrated that the sharpening
of the observed quasi-particle peak below Tc is attributed to the bose
condensation of holon pair. From the computed ratios of pseudogap to
both the superconducting temperature Tc and the pseudogap temperature as
a function of hole doping concentration x, we find that there exists a
universal scaling of these ratios with doping, that is, the hyperbolic scaling
behavior of the former, with
and near doping independence of the latter, are found.Comment: 5 pages, 5 figure
Origin of the Quasiparticle Peaks of Spectral Functions in High Cuprates
Based on the SU(2) slave-boson approach to the t-J Hamiltonian, we examine
the cause of the sharp peaks('quasiparticle' peaks) in the observed spectral
functions in high cuprates. The computed results reveal that the spectral
weight of the sharp peaks increases with hole doping rate in agreement with
observation. It is shown that the observed sharp peaks are attributed to the
enhancement of spinon pairing(spin singlet pair formation) by the presence of
holon pair bosons in the superconducting state.Comment: 4 pages, 6 figure
Doping dependence of bose condensation energy and correlations with spectral peak intensity and superfluid weight in high Tc cuprates
Based on our recent holon-pair boson theory of the t-J Hamiltonian (Phys.
Rev. B 64, 052501 (2001)) we report the doping dependence of the bose
condensation energy, superfluid weight and spectral peak intensity. We find a
universality of doping dependence in these physical quantities, by equally
showing an arch shape in the variations of their magnitudes with the hole
doping concentration. We find that all of these physical quantities scale well
with the positive charge carrier (hole) density x, but not with the electron
density 1-x for the entire range of hole doping. It is shown that the doping
dependence of the condensation energy U at T = 0 K is given by the relation,
with , the pairing gap at 0 K
and , a constant.Comment: 5 pages, 2 figure
Holon-pair boson theory based on the U(1) and SU(2) slave-boson approaches to the t-J Hamiltonian
To supplement our recent brief report on the theory of holon-pair boson
approach to the t-J Hamiltonian [S.-S. Lee and Sung-Ho Suck Salk, Phys. Rev. B
{\bf 64}, 052501(2001)], in this paper we present a full exposure to the
theory, detailed physical implications and predicted various physical
properties of high cuprates. We discuss the significance of coupling
(interplay) between the spin and charge degrees of freedom in the Heisenberg
interaction term of the t-J Hamiltonian. We discuss its importance in causing
the arch-shaped superconducting transition temperature and the pseudogap
(spin gap) temperature tangential to in the overdoped region in the
observed phase diagram of high cuprates. A universal parabolic scaling
behavior of (or ) with hole doping concentration is
predicted in agreement with observations, indicating that there exists
correlation between the pseudogap (spin gap) phase and the superconducting
phase through antiferromagnetic fluctuations. Our proposed holon-pair boson
theory is shown to be self-consistent in that it not only yields the arch
(dome) shape structure of but also reproduces various other physical
properties such as superfluid weight, bose condensation energy, spectral
function, optical conductivity and spin susceptibility, including their
temperature and doping dependence
Doping and temperature dependence of superfluid weights for high Tc cuprates
Using the improved slave-boson approach of the t-J Hamiltonian [Phys. Rev. B
64, 052501 (2001)] that we developed recently, we report the hole doping and
temperature dependence of the superfluid weight. It is shown that at low hole
doping concentration x and at low temperatures T there exists a propensity of a
linear decrease of the superfluid weight with temperature, and a
tendency of doping independence in the slope of vs. T in
accordance of the relation with , a constant. It is also demonstrated that Tc increases
with hole doping concentration x, reaches a saturation(maximum) at optimal
doping and decreases with increasing and in the overdoped region.
Such a reflex (decreasing) behavior of Tc is attributed to the weakening of
coupling between the spin(spinon pair order) and charge(holon pair order)
degrees of freedom in the overdoped region. All of these findings are in
agreement with SR measurements.Comment: 6 pages, 5 figure
Holon Pair Bose Condensation in High Cuprates; Symmetry Breaking and Supersymmetry Conditions
Using the t-J Hamiltonian of U(1) slave-boson symmetry, bose condensation is
discussed by showing the occurrence of symmetry breaking in the hole doped high
cuprates. The symmetry breaking is shown to take place with the d-wave
hole pairing, but not with the s-wave hole pairing. Based on a derived
supersymmetry Hamiltonian we find that there exists a possibility of
supersymmetry conditions in association with the pairing order parameters of
both spinon and holon.Comment: 4 pages, 2 figure
Snapshot projection optical tomography
We present a plenoptic microscopy configuration for 3D snapshot imaging,
which is dual telecentric and can directly record true projection images
corresponding with different viewing angles. It also allows blocking high-angle
stray rays without sacrificing the light collection efficiency. This
configuration named as snapshot projection optical tomography (SPOT) arranges
an objective lens and a microlens array (MLA) in a 4-f telecentric
configuration and places an aperture stop at the back focal plane of a relay
lens. We develop a forward imaging model for SPOT, which can also be applied to
existing light field microscopy techniques using an MLA as tube lens. Using the
developed system, we demonstrate snapshot 3D imaging of various fluorescent
beads and a biological cell, which confirms the capability of SPOT for imaging
specimens with an extended fluorophore distribution as well as isolated
fluorochromes. The transverse and vertical resolutions are measured to be 0.8
m and 1.6 m, respectively
T-structure and the Yamabe invariant
The Yamabe invariant is an invariant of a closed smooth manifold, which
contains information about possible scalar curvature on it. It is well-known
that a product manifold T^m\times B where T^m$ is the m-dimensional torus, and
B is a closed spin manifold of nonzero \hat{A}-genus has zero Yamabe invariant.
We generalize it to various T-structured manifolds, for example T^m-bundles
over such B whose transition functions take values in Sp(m,Z) (or
Sp(m-1,Z)\oplus \pm 1 for odd m)
Liouville-type theorems and applications to geometry on complete Riemannian manifolds
On a complete Riemannian manifold M with Ricci curvature satisfying
for , where A>0 is a constant, and r is the
distance from an arbitrarily fixed point in M. we prove some Liouville-type
theorems for a C^2 function satisfying for a function
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