We propose the local density approximation (LDA)+Gutzwiller method incorporating Green's function scheme to study the topological physics of correlated materials from the first-principles. Applying this method to typical mixed valence materials SmB6, we found its non-trivial Z2 topology, indicating that SmB6 is a strongly correlated topological insulator (TI). The unique feature of this compound is that its surface states contain three Dirac cones in contrast to most known TIs. PACS numbers:Most of Z 2 topological insulators (TI)[1-5] discovered up to now are semiconductors which are free of strong correlation effects and their topological nature can thus be predicted quite reliably by first principle calculations based on density functional theory (DFT) [6]. The Z 2 classification of band insulators has been generalized to interacting systems by looking at its response to external electric magnetic field, namely the topological magnetoelectric effect (TME) [7]. A correlated insulator is a TI if the θ-angle defines in TME is π. Given the TME theory and several simplifications [8], however, its application to realistic materials is still absent due to: (1) the lack of suitable compounds; (2) the difficulty to compute reliably correlated electronic structures from the firstprinciples. In this letter, we study a special class of materials, the mixed valence (MV) compounds, which contain rare-earth elements with non-integer chemical valence. By combining the Gutzwiller variational approach from the first-principles and the Green's function method for the TME, we found SmB 6 is a 3D correlated TI. Interestingly, it has three Dirac cones on the surface, in contrast to most of the known TIs.

China is developing a new generation of geostationary meteorological satellites called Fengyun-4 (FY-4), which is planned for launch beginning in 2016. Following upon the current FY-2 satellite series, FY-4 will carry four new instruments: the Advanced Geosynchronous Radiation Imager (AGRI), the Geosynchronous Interferometric Infrared Sounder (GIIRS), the Lightning Mapping Imager (LMI), and the Space Environment Package (SEP). The first satellite of the FY-4 series launched on 11 December 2016 is experimental, and the following four or more satellites will be operational. The main objectives of the FY-4 series are to monitor rapidly changing weather systems and to improve warning and forecasting capabilities. The FY-4 measurements are aimed at accomplishing 1) high temporal and spatial resolution imaging in 14 spectral bands from the visible, near-infrared, and infrared (IR) spectral regions; 2) lightning imaging; and 3) high-spectral-resolution IR sounding observations over China and adjacent regions. FY-4 will also enhance the space weather monitoring and warning with SEP. Current products from FY-2 will be improved by FY-4, and a number of new products will also be introduced. FY-4’s sounding and imaging data will be used to improve applications in a wide range of ocean, land, and atmosphere monitoring plus forecasting extreme weather (especially typhoons and thunderstorms); overall, FY-4 will contribute to more accurate understanding and forecasting of China’s weather, climate, environment, and natural disasters. This new generation of Chinese geostationary weather satellites is being developed in parallel with the new generation of geostationary meteorological satellite systems from the international community of satellite providers and is intended to be an important contribution to the global observing system.

No abstract

No abstract