Influence Of The Quasiparticle Spectral Weight In Fese On Spectroscopic, Magnetic, And Thermodynamic Properties

We report on an extensive experimental and numerical study of the low-energy electronic properties of superconducting FeSe single crystals, using point-contact Andreev reflection Spectroscopy (PCAR), specific heat, and London penetration depth measurements. Taking explicitly into account Fermi surface anisotropy and recently suggested orbital-selective quasiparticle spectral weights Zi (i = d(xy), d(x2-y2), d(xz), d(yz), d(z)(2)), our calculations quantitatively account for all our measurements as well as data from the literature, assuming that Z(yz) > Z(xz) > Z(xy). This study confirms the picture of a highly different quantum coherence of the Fe orbitals at the Fermi energy. In particular, the normal state properties (Sommerfeld coefficient and zero-temperature London penetration depth) strongly depend on the Zi values, which seem to be significantly sensitive to disorder.