AUTHOR=Torsello Daniele , Piatti Erik , Fracasso Michela , Gerbaldo Roberto , Gozzelino Laura , Yi Xiaolei , Xing Xiangzhuo , Shi Zhixiang , Daghero Dario , Ghigo Gianluca 

TITLE=Unusually weak irradiation effects in anisotropic iron-based superconductor RbCa2Fe4As4F2

JOURNAL=Frontiers in Physics

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2023.1336501

DOI=10.3389/fphy.2023.1336501

ISSN=2296-424X

ABSTRACT=<p>We report on the effects of 3.5 MeV proton irradiation in RbCa<sub>2</sub>Fe<sub>4</sub>As<sub>4</sub>F<sub>2</sub>, an iron-based superconductor with unusual properties in between those of the pnictides and of the cuprate high-temperature superconductors. We studied how structural disorder introduced by ion bombardment affects the critical temperature, superfluid density and gap values by combining a coplanar waveguide resonator technique, electric transport measurements and point-contact Andreev-reflection spectroscopy. We find an unusually weak dependence of the superconducting properties on the amount of disorder in this material when compared to other iron-based superconductors under comparable irradiation conditions. The nodal multigap state exhibited by pristine RbCa<sub>2</sub>Fe<sub>4</sub>As<sub>4</sub>F<sub>2</sub> is also robust against proton irradiation, with a two-band <italic>d</italic>-<italic>d</italic> model being the one that best fits the experimental data.</p>