Influence of the quasiparticle spectral weight in FeSe on spectroscopic, magnetic, and thermodynamic properties

Abstract

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 ${Z}_{i}$ ($i={d}_{xy},{d}_{{x}^{2}\ensuremath{-}{y}^{2}},{d}_{xz},{d}_{yz},{d}_{{z}^{2}}$), our calculations quantitatively account for all our measurements as well as data from the literature, assuming that ${Z}_{yz}g{Z}_{xz}g{Z}_{xy}$. 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 ${Z}_{i}$ values, which seem to be significantly sensitive to disorder.