Guang-Yu Guo

We combine theory and experiment to demonstrate that a carefully designed gradient meta-surface supports high-efficiency anomalous reflections for near-infrared light following the generalized Snell's law, and the reflected wave becomes a bounded surface wave as the incident angle exceeds a critical value. Compared to previously fabricated gradient meta-surfaces in infrared regime, our samples work in a shorter wavelength regime with a broad bandwidth (750-900 nm), exhibit a much higher conversion efficiency (∼80%) to the anomalous reflection mode at normal incidence, and keep light polarization unchanged after the anomalous reflection. Finite-difference-time-domain (FDTD) simulations are in excellent agreement with experiments. Our findings may lead to many interesting applications, such as antireflection coating, polarization and spectral beam splitters, high-efficiency light absorbers, and surface plasmon couplers.

The orthophosphate host family, A(I)B(II)PO(4) (A(I) = monovalent cation, B(II) = divalent cation), has recently been made available as phosphors that combine with near-UV lighting chips for use in solid-state white light-emitting diodes (LEDs). This study elucidates the crystalline structure and lattice parameters of the products via a solid-state reaction, using powder X-ray diffraction (XRD) and GSAS refinement. The versatility of the phosphor host A(I)B(II)PO(4) is established by examining isovalent substitutions of four cations in the structure-Li or K for A(I), Sr or Ba for B(II)-and three doped activators, RE = Eu(2+), Tb(3+), and Sm(3+). The luminescence properties, decay time, and Commission Internationale de l'Eclairage (CIE) chromaticity index are determined for various concentrations of these activators and metal constituents of the host. The thermal stabilities of all of these compounds are determined for the first time from the crystal structure and the coordination environment of the rare-earth metal. The morphology, composition, and particle size were measured in detail. Finally, density functional calculations were performed using the generalized gradient approximation plus an on-site Coulombic interaction correction (GGA+U) scheme to investigate the electronic structures of the KSrPO(4) system. A concise model was proposed to explain the luminescence mechanism.

Magneto-optical Kerr effect, normally found in magnetic materials with nonzero magnetization such as ferromagnets and ferrimagnets, has been known for more than a century. Here, using first-principles density functional theory, we demonstrate large magneto-optical Kerr effect in high-temperature noncollinear antiferromagnets ${\mathrm{Mn}}_{3}X\phantom{\rule{0.28em}{0ex}}(X=\mathrm{Rh},\phantom{\rule{0.28em}{0ex}}\mathrm{Ir},\phantom{\rule{0.28em}{0ex}}\mathrm{Pt})$, in contrast to usual wisdom. The calculated Kerr rotation angles are large, being comparable to that of transition-metal magnets such as bcc Fe. The large Kerr rotation angles and ellipticities are found to originate from the lifting of band double degeneracy due to the absence of spatial symmetry in the ${\mathrm{Mn}}_{3}X$ noncollinear antiferromagnets which together with the time-reversal symmetry would preserve the Kramers theorem. Our results indicate that ${\mathrm{Mn}}_{3}X$ would provide a rare material platform for exploration of subtle magneto-optical phenomena in noncollinear magnetic materials without net magnetization.

We demonstrate a self-assembly strategy for fabricating three dimensional (3D) metamaterials. This strategy represents the desired 3D curving prongs of the split ring resonators (SRRs) erected by metal stress force with appropriate thin film parameters. Transmittance spectra and field patterns corresponding to each resonance modes are calculated by finite element method (FEM). The eigen-modes of the SRRs can be excited by normal illumination with polarization state parallel to the erected SRRs, which are unlike for the cases of planar SRRs. This method opens a promising fabrication process for the application of tailored 3D SRRs.

MoS2 atomic layers have recently attracted much interest because of their two-dimensional structure as well as tunable optical, electrical, and mechanical properties for next-generation electronic and electro-optical devices. Here we have achieved facile fabrication of MoS2 thin films on CdS nanowires by cation exchange in solution at room temperature and importantly observed their extraordinary magnetic properties. We establish the atomic structure of the MoS2/CdS heterostructure by taking atomic images of the MoS2/CdS interface as well as performing first-principles density functional geometry optimizations and scanning transmission electron microscopy annular dark field image simulations. Furthermore, our first-principles density functional calculations for the MoS2/CdS heterostructure reveal that the magnetism in the MoS2/CdS heterostructure stems from the ferromagnetic MoS2 monolayer next to the MoS2/CdS interface. The ferromagnetism is attributed to the partial occupation of the Mo dx2–y2/dxy conduction band in the interfacial MoS2 monolayer caused by the mixed covalent–ionic bonding among the MoS2 and CdS monolayers near the MoS2/CdS interface. These findings of the ferromagnetic MoS2 monolayer with large spin polarization at the MoS2/semiconductor interface suggest a new route for fabrication of the transition metal dichalcogenide-based magnetic semiconductor multilayers for applications in spintronic devices.