Band structure renormalization and weak pseudogap behavior in Na_{0.33}CoO_2: Fluctuation exchange study based on a single band model

Based on a single band Hubbard model and the fluctuation exchange approximation, the effective mass and the energy band renormalization in Na$_{0.33}$CoO$_2$ is elaborated. The renormalization is observed to exhibit certain kind of anisotropy, which agrees qualitatively with the angle-resolved photoemission spectroscopy (ARPES) measurements. Moreover, the spectral function and density of states (DOS) in the normal state are calculated, with a weak pseudogap behavior being seen, which is explained as a result of the strong Coulomb correlations. Our results suggest that the large Fermi surface (FS) associated with the $a_{1g}$ band plays likely a central role in the charge dynamics.Comment: 5 pages, 5 figure

Orbital-transverse density-wave instabilities in iron-based superconductors

Besides the conventional spin-density-wave (SDW) state, a new kind of orbital-transverse density-wave (OTDW) state is shown to exist generally in multi-orbital systems. We demonstrate that the orbital character of Fermi surface nesting plays an important role in density responses. The relationship between antiferromagnetism and structural phase transition in LaFeAsO (1111) and BaFe$_2$As$_2$ (122) compounds of iron-based superconductors may be understood in terms of the interplay between the SDW and OTDW with a five-orbital Hamiltonian. We propose that the essential difference between 1111 and 122 compounds is crucially determined by the presence of the two-dimensional $d_{xy}$-like Fermi surface around (0,0) being only in 1111 parent compounds.Comment: several parts were rewritten for clarity. 6 pages, 3 figures, 1 tabl

Mottness induced phase decoherence suggests Bose-Einstein condensation in overdoped cuprate high-temperature superconductors

Recent observations of diminishing superfluid phase stiffness in overdoped cuprate high-temperature superconductors challenges the conventional picture of superconductivity. Here, through analytic estimation and verified via variational Monte Carlo calculation of an emergent Bose liquid, we point out that Mottness of the underlying doped holes dictates a strong phase fluctuation of the superfluid at moderate carrier density. This effect turns the expected doping-increased phase stiffness into a dome shape, in good agreement with the recent observation. Specifically, the effective mass divergence due to "jamming" of the low-energy bosons reproduces the observed nonlinear relation between phase stiffness and transition temperature. Our results suggest a new paradigm, in which the high-temperature superconductivity in the cuprates is dominated by physics of Bose-Einstein condensation, as opposed to pairing-strength limited Cooper pairing.Comment: 6+3 pages, 4+1 figure

The Spatial Constraint Requiring Organogenetic Termination: Supplemental to Haeckel and von Baer for Development and Evolution

In this article, it is pointed out that the requirement for organogenetic termination is the new spatial constraint for animal development and heredity, based on that: (a) organogenesis manifests limitation in time and possession of termination, while infinite cell proliferation known as cancer is lethal; (b) the notable indeterminate growth in some fishes and a few outgrowing skin derivatives reversely demonstrates that termination is required for organogenesis inside the animal. In further, it is supplemented this new spatial constraint to Haeckel and von Baer for development and evolution. While not influencing the temporal and spatial reorganization of morphogenesis during evolution, it places restrictions on alteration of organogenetic mechanisms themselves, as that: (a) addition of new induction mechanism or elimination of termination mechanism would usually cause endless organogenesis, liable to become lethal; (b) addition of new termination mechanism or elimination of induction mechanism in evolution not be affected by this spatial constraint. Finally, it is identified this spatial constraint as partial convergence and partial difference with Haeckel’s recapitulation, and as restriction onto Baer’s tree. It is perspectives to use the method of mathematical probability and statistics to study the spatial constraint of development onto evolution in future.&nbsp