Twofold role of columnar defects in iron based superconductors. (31st July 2020)

• Record Type: Journal Article
• Authors: Torsello, D; Gerbaldo, R; Gozzelino, L; Laviano, F; Takahashi, A; Park, A; Pyon, S; Ichinose, A; Tamegai, T; Ghigo, G
• Is Part Of: Superconductor science & technology. Volume 33:Number 9(2020:Sep.)
• Publication Date: 2020-07-31
• Subjects: iron-based superconductors -- heavy-ion irradiation -- microwave surface impedance -- critical current density -- magneto-optical imaging; Superconductivity -- Periodicals; Superconductors -- Periodicals; 537.623
• DOI: 10.1088/1361-6668/aba350
• Languages: English
• ISSNs: 0953-2048

Abstract

Abstract: We report on the introduction of columnar defects in Ba1− x K x Fe2 As2 and BaFe2 (As1− x P x )2 single crystals via 1.2 GeV Pb irradiation. Scanning transmission electron microscopy analysis proves the formation of continuous defects along the ion tracks, with a diameter of about 3 nm, and a planar density compatible with the irradiation fluence. The twofold role of such defects, i.e. as pair breakers as well as pinning centers, is investigated by a microwave technique, allowing us to determine critical temperature T c, surface impedance and penetration depth λ L, and by magneto-optical imaging and superconducting quantum interference device magnetometry to evaluate the critical current density J c . The decrease of T c is quite modest and, together with λ L modifications, testifies the increase of pair-breaking scattering following irradiation. The dependence of J c on irradiation dose and temperature is due to the pinning landscape induced by the columnar defects, and shows the existence of an optimal irradiation dose to enhance the critical current.