The in-plane longitudinal and Hall resistivities, ρxx and ρxy, of superconducting NaFe1-xCoxAs (NFCA) single crystals with x = 0.022 and 0.0205 in the mixed state and the normal state were measured to study the electrical transport properties in nearly optimum-doping iron-based superconductors. The resistivities under magnetic fields show thermally activated behavior and a power law magnetic field dependence of activation energy has been obtained. Due to the weak flux pinning, there is no sign reversal of Hall resistivities observed for NFCA with either x = 0.022 or 0.0205. The correlation between longitudinal and Hall resistivities shows that the scaling behavior of |ρxy| ∝ (ρxx)(β) with the exponent β ≈ 2.0 is in agreement with theoretical predictions for weak-pinning superconductors. Anisotropic upper critical fields and coherence lengths with an anisotropy ratio of γ ≈ 1.63 have been deduced. Furthermore, the normal-state transport properties show that the anomalies of the linear-T resistivity, the T(2)-dependent cotangent of the Hall angle, the linear-T-like Hall number, and the magnetoresistance, which can be scaled by the modified Kohler rule, are analogous to those observed on optimally doped high-Tc superconducting cuprates and other pnictides. The longitudinal resistivity can be understood within a widely accepted scenario of the spin density-wave quantum critical point, while the transverse resistivity requires some further explanation. It is suggested that all the transport anomalies should be simultaneously taken into account when developing theory.

It has been recently demonstrated1 that the ballistic component (photons that arrive first) through random media can be separated in time from the diffused scattering component. This report addresses time-resolved two-dimensional imaging of the ballistic signal emanating from point and plane objects located in turbid media. We used an ultrafast Kerr gating system, consisting of a mode-locked ps glass laser, a CS2 Kerr shutter, and a two-dimensional change-coupled device camera with 600400 spatial resolution to record the images. A pair of 200 m point sources separated by 400 m in water solution with scattering beads, was resolved using a fluorescence time gating. A U.S. Air Force bar-test chart was placed inside the water solution filled with beads at OD = 4. The diffused and ballistic signals from the chart were imaged at different times. At T = 0, we obtained a clear bar image with the spatial resolution 500 m. These key observations are the result of ballistic photons arriving first at the Kerr gate. When the gating time was delayed, the images broadened and blurred. The time difference between the ballistic and the diffusive scattering components was measured to be 15 ps.