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

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

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

The Electromagnetic Unification of Four Forces: Supporting Planck and Rectifying Einstein

It was Zi-Jian Cai and the satellite operators from China, India and USA who led the world people in television to make the electromagnetic unification of four forces, and altogether achieved many important progressions, such as the spatially localized electromagnetic mass structure, the electromagnetic orienting force, the electromagnetic multi-hairy structure, the non-relativity of ideal time and space, the electromagnetic curve and red-shift for gravity, the stable strong force from electromagnetic multi-hairy hybrid, the weak processes from hybrid split and oscillatory pair of bound electrical fields of neutrino, and so on. Especially, it was an important supplement to general relativity of Einstein by the spatially localized electromagnetic mass structure and electromagnetic orienting force, unifying the gravitational force with electromagnetic force, while explaining the neutrino of small mass moving at light speed. Due to the mistake of Einstein in explaining the essence of mass, it would in turn mislead the mathematical field unification later in physics related to mass. Besides, it was unfortunately also a mistake of Einstein on concept of relativity for ideal time and space, which was proven to manifest as non-relativity. On the other hand, it was explained the Planck quantum as the dependence of photo energy only on frequency due to the identical strength of electrical hair of electron and emitted photo, supporting the classical quantum theory. It was herein accomplished the electromagnetic unification of four forces, supporting Planck and rectifying Einstein.&nbsp

Recent Progressions on Peripheral Hypotheses of Hypothalamic Aging

Background: It is well known that the changes of hypothalamus in control of hormones determine the chronological manifestations of aging in mammals.Aim: It is aimed to review the progressions on recently hypothesized peripheral mechanisms responsible for the senescent changes of the hypothalamic nuclei and secretion.Methods: It was searched the papers from Pubmed and Baidu, and then analyzed and summarized.Results and Discussions: (a) It was proposed by Cai that the decrease in slow-wave sleep (SWS) resulting from continual skin aging cause both decrease in secretion of growth hormone (GH) and degeneration of suprachiasmatic nucleus(SCN) for hypothalamus. (b) It was soon hypothesized by the Europeans that the increase in body fat be responsible for the degeneration of male hypothalamic preoptic sexually dimorphic nucleus (SDN-POA), which was supported by the increment of aromatase converting testosterone to estradiol as proposed by Cohen, with testosterone required to maintain SDN-POA. In parallel, it was speculated the aging of female ovary toward menopause as acceleration and precocity similarly in association with the corresponding senescent changes in lipid, aromatase and estradiol. (c) It was the hypothalamic paraventricular nucleus (PVN) that retained neuron number unchanged during aging for psychological stress..Conclusion: It is summarized that the hypothalamic senescence resulting from these peripheral mechanisms shifts the functional balance among these three hypothalamic systems toward aging