11,245 research outputs found
Microscopic Inhomogeneity and Superconducting Properties of a Two-dimensional Hubbard Model for High- Cuprate
Recent scanning tunneling microscopy measurements on cuprate superconductors
have revealed remarkable spatial inhomogeneities in the single-particle energy
gap. Using cellular dynamical mean-field theory, we study the zero temperature
superconducting properties of a single-band Hubbard model with a spatial
modulation of the electron density. We find that the inhomogeneity in the
electronic structure results in a substantial spatial variation in the
superconducting order parameter and single-particle energy gap, reminiscent of
the experimental results. In particular, we find that the order parameter and
gap amplitudes in the hole-rich regions are significantly enhanced over the
corresponding quantities in a uniform system, if the hole-rich regions are
embedded in regions with smaller hole density.Comment: 6 pages, 4 figures, and 2 table
Enhanced Superconductivity in Superlattices of High- Cuprates
The electronic properties of multilayers of strongly correlated models for
cuprate superconductors are investigated using cluster dynamical mean-field
techniques. We focus on combinations of underdoped and overdoped layers and
find that the superconducting order parameter in the overdoped layers is
enhanced by the proximity effect of the strong pairing scale originating from
the underdoped layers. The enhanced order parameter can even exceed the maximum
value in uniform systems. This behavior is well reproduced in slave-boson
mean-field calculations which also find higher transition temperatures than in
the uniform system.Comment: 4 pages, 4 figure
Coexistence of strong nematic and superconducting correlations in a two-dimensional Hubbard model
Using a dynamic cluster quantum Monte Carlo approximation, we study a
two-dimensional Hubbard model with a small orthorhombic distortion in the
nearest neighbor hopping integrals. We find a large nematic response in the
low-frequency single-particle scattering rate which develops with decreasing
temperature and doping as the pseudogap region is entered. At the same time,
the d-wave superconducting gap function develops an s-wave component and its
amplitude becomes anisotropic. The strength of the pairing correlations,
however, is found to be unaffected by the strong anisotropy, indicating that
d-wave superconductivity can coexist with strong nematicity in the system.Comment: 4 pages, 4 figures, published as PRB 84, 220506(R) (2011
Confidence-aware Levenberg-Marquardt optimization for joint motion estimation and super-resolution
Motion estimation across low-resolution frames and the reconstruction of
high-resolution images are two coupled subproblems of multi-frame
super-resolution. This paper introduces a new joint optimization approach for
motion estimation and image reconstruction to address this interdependence. Our
method is formulated via non-linear least squares optimization and combines two
principles of robust super-resolution. First, to enhance the robustness of the
joint estimation, we propose a confidence-aware energy minimization framework
augmented with sparse regularization. Second, we develop a tailor-made
Levenberg-Marquardt iteration scheme to jointly estimate motion parameters and
the high-resolution image along with the corresponding model confidence
parameters. Our experiments on simulated and real images confirm that the
proposed approach outperforms decoupled motion estimation and image
reconstruction as well as related state-of-the-art joint estimation algorithms.Comment: accepted for ICIP 201
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