Charge transport in Ba_1−xRb_xFe₂As₂ single crystals

Recent studies in heavily hole-doped iron-based superconductor RbFe₂As₂ have suggested the emergence of novel electronic nematicity directed along the Fe-As direction, 45° rotated from the usual nematicity ubiquitously found in BaFe₂As₂ and related materials. This motivates us to study the physical properties of Ba_1−xRb_xFe₂As₂, details of which remain largely unexplored. Here we report on the normal-state charge transport in Ba_1−xRb_xFe₂As₂ superconductors by using high-quality single crystals in the range of Rb concentration 0.14 ≤ x ≤ 1.00. From the systematic measurements of the temperature dependence of electrical resistivity ρ(T), we find a signature of a deviation from the Fermi liquid behavior around the optimal composition, which does not seem related to the antiferromagnetic quantum criticality but has a potential link to hidden nematic quantum criticality. In addition, electron correlations derived from the coefficient of T² resistivity show a marked increase with Rb content near the heavily hole-doped end, consistent with the putative Mott physics near the 3d⁵ electron configuration in iron-based superconductors. (author)