Tracing the $s_{\pm }$-symmetry in iron pnictides by controlled disorder

Abstract

Consecutive proton irradiation of iron pnictides reduces the superconducting transition temperature to decrease monotonically. Our systematic optical THz investigations of Ba(Fe${}_{0.9}$Co${}_{0.1}$)${}_2$As${}_2$ thin films reveal, however, that the low-energy superconducting gap is first suppressed, but recovers for higher irradiation doses. At the same time the decrease of the superfluid density with disorder comes to a halt. These observations are in excellent agreement with theoretical calculations, which predict a disorder-induced transition of the order parameter from $s_{\pm }$ to $s_{++}$ symmetry. Thereby we solve the longstanding puzzle of the iron pnictides gap symmetry in favor of $s_{\pm }$-symmetry and demonstrate THz spectroscopy as a tool to determine the symmetry of the superconducting order parameter.

References in corpus (8)

• Antiferromagnetic order and spin dynamics in iron-based superconductors
• Iron-Based Superconductors: current status of materials and pairing mechanism
• Using Gap Symmetry and Structure to Reveal the Pairing Mechanism in Fe-based Superconductors
• Where Are the Extra d Electrons in Transition-Metal Substituted Fe Pnictides?
• Disorder-induced topological change of the superconducting gap structure in iron pnictides
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Versatile fluoride substrates for Fe-based superconducting thin films
• Manifestation of impurity induced s_{+-} -> s_{++} transition: multiband model for dynamical response functions

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• Enhanced upper critical field in Co-doped Ba122 superconductors by lattice defect tuning
• Multi-band $s_{++}$ superconductivity in ${\text{V}}_3\text{Si}$ determined from the response to a controlled disorder
• Electrodynamic response of Ba(Fe1-xRhx)2As2 across the s+- to s++ order parameter transition
• Reentrant phases in electron-doped ${\text{EuFe}}_2{\text{As}}_2$: spin glass and superconductivity
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• Impurity effects on spin dynamics in magnetic and superconducting iron pnictides and chalcogenides
• Decisive proofs of the $s_{\pm }\to s_{++}$ transition in the temperature dependence of the magnetic penetration depth
• Ion-selective scattering studied by the variable-energy electron irradiation of Ba${}_{0.2}$K${}_{0.8}$Fe${}_2$As${}_2$ superconductor
• Thermodynamics of $s_{\pm }-to-s_{++}$ transition in iron pnictides in the vicinity of the Born limit