Electrochemical （EC） reactions play vital roles in many disciplines, and its molecular-level understanding is highly desired, in particular under reactions. The vibration spectroscopy is a powerful in situ technique for chemical analysis, yet its application to EC reactions is hindered by the strong attenuation of infrared （IR） light in both electrodes and electrolytes. Here we demonstrate that by incorporating appropriate sub-wavelength plasmonic structures at the metal electrode, the IR field at the EC interface can be greatly enhanced via the excitation of surface plasmon. This scheme facilitates in situ vibrational spectroscopic studies, especially using the surface-specific sum-frequency generation technique.
The newly discovered iron-chalcogenide superconductorKxFe2ySe2exhibits a distinct electronic structure from other iron-based superconductors.Exploiting polarization-dependent angle-resolved photoemission spectroscopy,we have determined the orbital characters of band structure in aKxFe2ySe2superconductor.To a large extent,we find thatKxFe2ySe2superconductor shares similar orbital characters with other iron-based superconductors,but with its own characteristics.For example,we have resolved two highly degenerate electron cylinders around the zone corner in the s and p geometries,respectively,indicating negligible interactions between them.Moreover,in contrast to the band calculation results,the small electron pocket around Z is found to be mainly consisted of the d z 2 orbital.The determined orbital characters would help to construct a realistic model forKxFe2ySe2.
Graphene-doped polymer nanofibers are fabricated by taper drawing of solvated polyvinyl alcohol doped with liquid-phase exfoliated graphene flakes.Nanofibers drawn this way typically have diameters measured in hundreds of nanometers and lengths in tens of millimeters;they show excellent uniformity and surface smoothness for optical waveguiding.Owing to their tightly confined waveguiding behavior,light–matter interaction in these subwavelength-diameter nanofibers is significantly enhanced.Using approximately 1350-nm-wavelength femto-second pulses,we demonstrate saturable absorption behavior in these nanofibers with a saturation threshold down to 0.25 pJ pulse^(-1)(peak power,1.3 W).Additionally,using 1064-nm-wavelength nanosecond pulses as switching light,we show all-optical modulation of a 1550-nm-wavelength signal light guided along a single nanofiber with a switching peak power of,3.2 W.
Angle-resolved photoemission spectroscopy （ARPES） has played an important role in determining the band structure and the superconducting gap structure of iron-based superconductors. In this paper, from the ARPES perspective, we briefly review the main results from our group in recent years on the iron-based superconductors and their parent compounds, and depict our current understanding on the antiferromagnetism and superconductivity in these materials.
