Low-temperature transport properties of doped Ba0.57K0.43Fe2As2 superconductors in high magnetic field

For high-critical-temperature (high-${T}_{\text{c}}$) superconductors, the normal state transport properties at low temperatures are of great importance to understand the Fermi surface structure and carrier profile. In this work we studied the doped ultrathin ${\mathrm{Ba}}_{0.57}{\mathrm{K}}_{0.43}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ system, a member of the optimally doped 122-type multigapped iron-based superconductors with complex superconducting gap structure. To explore the normal state resistivity below the zero-field superconducting ${T}_{\text{c}}$, both Co and Zn dopants were substituted into the superconducting ${\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ layer to suppress the superconductivity. The temperature dependence of in-plane resistivity below ${T}_{\text{c}}$ reveals a typical metallic behavior with the magnetic fields up to 45 T along $c$ axis. A linear dependence of Hall resistivity $({\ensuremath{\rho}}_{xy})$ is observed for ${\mathrm{Ba}}_{0.57}{\mathrm{K}}_{0.43}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ and ${\mathrm{Ba}}_{0.57}{\mathrm{K}}_{0.43}{({\mathrm{Fe}}_{0.96}{\mathrm{Zn}}_{0.04})}_{2}{\mathrm{As}}_{2}$ at high magnetic field, indicating a conventional metal profile. Nevertheless, the Co dopants lead to a decreasing $d{\ensuremath{\rho}}_{xy}/dH$ when the field is above 20 T. Such transformation of carrier transport properties may be contributed by band shift within a two-carrier model.