The electronic structure of NaIrO3_3, Mott insulator or band insulator?

Motivated by the unveiled complexity of nonmagnetic insulating behavior in pentavalent post-perovskite NaIrO$_3$, we have studied its electronic structure and phase diagram in the plane of Coulomb repulsive interaction and spin-orbit coupling (SOC) by using the newly developed local density approximation plus Gutzwiller method. Our theoretical study proposes the metal-insulator transition can be generated by two different physical pictures: renormalized band insulator or Mott insulator regime. For the realistic material parameters in NaIrO$_3$, Coulomb interaction $U=2.0 (J=U/4)$ eV and SOC strength $\eta=0.33$ eV, it tends to favor the renormalized band insulator picture as revealed by our study.Comment: 5 pages, 4 figure

Cylindrical Cloak with Axial Permittivity/Permeability Spatially Invariant

In order to reduce the difficulties in the experimental realizations of the cloak but still keep good performance of invisibility, we proposed a perfect cylindrical invisibility cloak with spatially invariant axial material parameters. The advantage of this kind of TE (or TM) cloak is that only rho and phi components of mu (or epsilon) are spatially variant, which makes it possible to realize perfect invisibility with two-dimensional (2D) magnetic (or electric) metamaterials. The effects of perturbations of the parameters on the performance of this cloak are quantitatively analyzed by scattering theory. Our work provides a simple and feasible solution to the experimental realization of cloaks with ideal parameters

Primordial Black Holes from Sound Speed Resonance during Inflation

We report on a novel phenomenon of the resonance effect of primordial density perturbations arisen from a sound speed parameter with an oscillatory behavior, which can generically lead to the formation of primordial black holes in the early Universe. For a general inflaton field, it can seed primordial density fluctuations and their propagation is governed by a parameter of sound speed square. Once if this parameter achieves an oscillatory feature for a while during inflation, a significant non-perturbative resonance effect on the inflaton field fluctuations takes place around a critical length scale, which results in significant peaks in the primordial power spectrum. By virtue of this robust mechanism, primordial black holes with specific mass function can be produced with a sufficient abundance for dark matter in sizable parameter ranges.Comment: 6 pages, 4 figures; v2: figures replotted with corrections, analysis extended, version accepted by Phys.Rev.Let

Thinking about ophthalmology teaching team building

Building high performance teaching team of ophthalmology has a very important role for teachers' professional development and the improvement of the quality of ophthalmology personnel training. In this paper, the situation and existing problems of ophthalmology teaching team, the meaning of building ophthalmology teaching team, and the strategies for building team were considered