Non-magnetic impurity effect in two-gap superconductor Lu2Fe3Si5

Electronic structure and Fermi surface of iron-based superconductors R2Fe3Si5 (R = Lu;Y;Sc) from first principles

“…Such an interaction enables also the extended s-wave (s± wave) superconductivity, for which the sign of the order parameter would be opposite for the hole-and electronlike FS sheets. This is consistent with recent experimental data [20,25,[28][29][30][31][32], in analogy to the situation in the high-Tc (oxy)pnictides [42].…”

“…Nevertheless, any unconventional (non-phononic) mechanism of their superconductivity may be similar to those already postulated for a majority of iron-based compounds. These conclusions are in accord with the findings of recent various experiments presented in [28][29][30][31][32]. …”

“…The anisotropy of their superconducting properties, anomalous upper critical fields (in Lu2Fe3Si5), and inter-band electron scattering in the case of two weak-coupled distinct gaps opened on the whole Fermi surface (FS) sheets, indicated that they are rather quasi-2D superconductors [26][27][28][29]. Furthermore, some recent works [30][31][32] focused on the effect of doping by non-magnetic impurities and atomic disorder induced by the neutron irradiation, both causing a fast suppression of TC in Lu2Fe3Si5, have questioned the conventional (phononic) mechanism of SC in the (Lu;Y;Sc)2Fe3Si5 family, revealing the significance of spin fluctuations in formation of the SC state [32]. The same effect was observed in the high-TC (oxy)pnictides after irradiation and, hence, it might be universal for all iron-based superconductors.…”

Mean-field calculations on the magnetic properties of the two-gap superconductor Lu2Fe3Si5

“…The experimental results of the upper critical field from resistivity measurements also strongly indicate the presence of two distinct superconducting gaps in Lu 2 Fe 3 Si 5 although the behavior is slightly different from that of the typical two-gap superconductor MgB 2 [12]. Detailed studies of non-magnetic effects tell us that a slight substitution of non-magnetic impurities will increase the interband scattering and cause averaging the amplitude of two gaps, which leads to the drastic suppression of T c [13,14].…”

Two-band superconductivity featuring different anisotropies in the ternary iron silicide Lu2Fe3Si5

“…Specific heat, 9 penetration depth, 10 and thermal conductiv-ity studies 11 suggest that the superconducting gaps are fully opened on the whole Fermi surface. However, interestingly, a rapid decrease in T c is reported when a small amount of nonmagnetic impurities replace some of Lu or Si sites, [12][13][14] which leads us to speculate that the sign of the superconducting gap functions is reversing on and/or between the Fermi surfaces such as the s ± -wave state. In order to reveal the peculiar superconducting properties in the multigap superconductor Lu 2 Fe 3 Si 5 , it is crucial to investigate the detailed nature of the multigap structure.…”