Doping dependence of resistivity, upper critical field and its anisotropy in overdoped Ba 1– x K x Fe 2 As 2 ( x = 0.6–1) single crystals

作者：Ke Shi, Wenshan Hong, Y. Li, Minjie Zhang, Yongqi Han, Yu Tao Zhao, Jiating Wu, Ze Wang, Langsheng Ling, Chuanying Xi, Li Pi, Huiqian Luo, Zhaosheng Wang · 发表于：Chinese Physics B · 年份：2025 · DOI：10.1088/1674-1056/ae1df1 · 被引用次数：1 · 研究领域：Iron-based superconductors research、Rare-earth and actinide compounds、Superconductivity in MgB2 and Alloys

Abstract Temperature-dependent resistivity, upper critical field H c2 and its anisotropy in overdoped superconducting Ba 1− x K x Fe 2 As 2 ( x = 0.6–1) single crystals have been measured in steady magnetic fields up to 44 T and low temperatures down to 0.4 K. Analysis using both the quadratic term and power-law fitting demonstrates that the in-plane resistivity ρ ab ( T ) progressively approaches the Fermi-liquid T 2 behavior with increasing K doping and reaches a saturation plateau at x ≈ 0.8. The temperature dependence of both H c 2 a b and H c 2 c follows the Werthamer–Helfand–Hohenberg model, incorporating orbital and spin paramagnetic effects. For x ≤ 0.8, the orbital effect dominates for H ∥ ab , while the Pauli paramagnetic effect prevails for H ∥ c . For x > 0.8, the Pauli paramagnetic effect becomes dominant in both crystallographic directions. The anisotropy of H c2 (0) exhibits a discontinuity in its dependence on K doping concentration with a significant enhancement at x = 0.8 and a maximum at x = 0.9. These experimental results indicate that the electron correlation effect is enhanced in the heavily overdoped Ba 1− x K x Fe 2 As 2 system where the underlying symmetries are broken due to the Fermi surface reconstruction before x = 0.9.