We performed detailed temperature-dependent optical measurements on optimally doped Ba0.6K0.4Fe2As2 single crystal, We examine the changes of the in-plane optical conductivity spectral weight in the normal state and the evolution of the superconducting condensate in the superconducting state. In the normal state, the low-frequency spectral weight shows a metallic response with an arctan （T） dependence, indicating a T-linear scattering rate behavior for the carriers. A high energy spectral weight transfer associated with the Hund＇s coupling occurs from the low frequencies below 4000 cm^-1 5000 cm^-1 to higher frequencies up to at least 104 cm^-1. Its temperature dependence analysis suggests that the Hund＇s coupling strength is continuously enhanced as the temperature is reduced. In the superconducting state, the FGT sum rule is conserved according to the spectral weight estimation within the conduction bands, only about 40% of the conduction bands participates in the superconducting condensate indicating that Ba0.6K0.4Fe2As2 is in dirty limit.
The response of superconducting Nb films with a diluted triangular and square array of holes to a perpendicular magnetic field are investigated.Due to small edge-to-edge separation of the holes,the patterned films are similar to multi-connected superconducting islands.Two regions in the magnetoresistance R(H) curves can be identified according to the field intervals of the resistance minima.Moreover,in between these two regions,variation of the minima spacing was observed.Our results provide strong evidence of the coexistence of interstitial vortices in the islands and fluxoids in the holes.
The response of superconducting Nb films with a diluted triangular and square array of holes to a perpendicular magnetic field are investigated. Due to small edge-to-edge separation of the holes, the patterned films are similar to multi-connected superconducting islands. Two regions in the magnetoresistance R（H） curves can be identified according to the field intervals of the resistance minima. Moreover, in between these two regions, variation of the minima spacing was observed. Our results provide strong evidence of the coexistence of interstitial vortices in the islands and fluxoids in the holes.
We measured the infrared reflectivity of BaFe1.904Ni0.096As2 single crystal from room temperature down to 20 K. Two Drude terms and a Lorentz term well describe the real part of the optical conductivity σ1 （ω）. We fit the reciprocal of static optical conductivity 1/σ1（0） by the power law ρ （T）=ρo＋ATn with n= 1.6. The ＂broad＂ Drude component exhibits an incoherent background with a T-independent scattering rate 1/τb, while the other ＂narrow＂ one reveals a T-quadratic scattering rate 1/τn, indicating a hidden Fermi-liquid behavior in BaFe1.904Nio.096As2 compound.
