Doping evolution of the superconducting gap structure in the underdoped iron arsenide Ba1-xKxFe2As2 revealed by thermal conductivity

Abstract

The thermal conductivity kappa of the iron-arsenide superconductor Ba1-xKxFe2As2 was measured for heat currents parallel and perpendicular to the tetragonal c axis at temperatures down to 50 mK and in magnetic fields up to 15 T. Measurements were performed on samples with compositions ranging from optimal doping (x = 0.34; Tc = 39 K) down to dopings deep into the region where antiferromagnetic order coexists with superconductivity (x = 0.16; Tc = 7 K). In zero field, there is no residual linear term in kappa(T) as T goes to 0 at any doping, whether for in-plane or inter-plane transport. This shows that there are no nodes in the superconducting gap. However, as x decreases into the range of coexistence with antiferromagnetism, the residual linear term grows more and more rapidly with applied magnetic field. This shows that the superconducting energy gap develops minima at certain locations on the Fermi surface and these minima deepen with decreasing x. We propose that the minima in the gap structure arise when the Fermi surface of Ba1-xKxFe2As2 is reconstructed by the antiferromagnetic order.

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• Using electron irradiation to probe iron - based superconductors
• Robust s+/- pairing in CaK[Fe(1-x)Ni(x)]4As4$ (x = 0 and 0.05) from the response to electron irradiation
• Topological Phase Transitions in Line-nodal Superconductors
• Effect of proton irradiation on the normal state low-energy excitations of Ba(Fe${}_{1-x}$Rh${}_x$)${}_2$As${}_2$ superconductors
• Infrared probe of the gap evolution across the phase diagram of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Superconducting gap symmetry in BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$ superconductor
• Dependence of the absolute value of the penetration depth in $(\mathbf{B}{\mathbf{a}}_{1-\mathbf{x}}{\mathbf{K}}_{\mathbf{x}})\mathbf{F}{\mathbf{e}}_2\mathbf{A}{\mathbf{s}}_2$ on doping
• Ultrasound evidence for multicomponent superconducting order parameter in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ with electron quadrupling phase
• Critical behavior around the fixed points driven by fermion-fermion interactions and disorders in the nodal-line superconductors
• Evolution of superconducting gap anisotropy in hole-doped 122 iron pnictides