Wiedemann-Franz law in iron-based superconductor Fe sub(1+d)Te sub(1-x)Se sub(x)

We present results of measurements of the transport phenomena in the series of Fe sub(1+d)Te sub(1-x)Se sub(x) single crystals. Namely, we investigate the longitudinal and transverse electrical and thermal conductivities in the parent compound Fe sub(1+d)Te as well as superconducting Fe sub(1+d)Te sub(0.85)Se sub(0.15) and Fe sub(1+d)Te sub(0.59)Se sub(0.41). This set of data allows us to verify validity of the Wiedemann-Franz law in the systems studied and consequently it is stated that the electronic system in the paramagnetic phase of Fe sub(1+d)Te behaves like the Fermi liquid being predominantly elastically scattered. In contrast, low temperature properties of Fe sub(1+d)Te sub(0.85)Se sub(0.15) and Fe sub(1+d)Te sub(0.59)Se sub(0.41) are affected likely by the emergence of antiferromagnetic fluctuations, which are expected to be ( pi ,0) and ( pi , pi ), respectively. These seem to be coupled with the hole-like band in case of Fe sub(1+d)Te sub(0.85)Se sub(0.15), whereas with the electron-like band in case of Fe sub(1+d)Te sub(0.59)Se sub(0.41).