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

Abstract

We report detailed studies of the upper critical field and low-temperature specific heat in the two-gap superconductor Lu2Fe3Si5. The anisotropy of the upper critical field suggests that the active band is quasi-one-dimensional. Low-temperature specific heat in magnetic fields reveals that the virtual Hc2 in the passive band is almost isotropic. These results strongly indicate that the two bands have two different anisotropies, similar to the typical two-gap superconductor MgB2, and their interplay may be essential to the two-gap superconductivity in Lu2Fe3Si5.

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“…[20] Furthermore, different anisotropies of the two bands in Lu 2 Fe 3 Si 5 was also recently reported. [21] Because of their various interesting properties, the search for new 235 compounds that might possess higher T c with magnetic ordering is of great importance to the study of superconductivity, magnetism and the relationship between them.…”

The electronic structure of rare-earth iron silicide R2Fe3Si5 superconductors

“…The dimensionality of active and passive superconducting bands for twogap SC in 235-type Fe-based systems, considered in experimental studies [29], remains still unclear. Holelike bands are assumed to create the quasi-1D FS pieces, while the 3D electronlike pillows in sheet III, possibly originate from the passive band.…”

“…The interband electron scattering between these two weak-coupled gaps opened on the whole Fermi surface (FS) is the reason for an observed anisotropy of superconducting properties in the 235-type iron silicides being rather quasi-2D superconductors [24,25,26,27,28,29]. Furthermore, the conventional (phononic) character of an SC mechanism in Lu 2 Fe 3 Si 5 has been questioned by a fast suppression of T c caused by non-magnetic impurities and atomic disorder induced by the neutron irradiation [30,31,32].…”

“…The differences in dimensionality of two FS sheets of this compound appeared to be crucial for its twoband SC phenomenon. In the (Lu;Y;Sc) 2 Fe 3 Si 5 family, the larger gap may be connected with quasione-dimensional (quasi-1D) parts of the holelike FS sheets, while the socalled passive band may contribute to the 3D electronlike FS sheet [29]. Furthermore, in these superconductors, the orbital-dependent contributions of the Fe 3d electrons to the FSs are partially separated from one another [33].…”

Specific Heat and Upper Critical Field of Sc5Ir4Si10Superconductor

“…21,28,29) Therefore, to describe the H c2 curves in the present case, the commonly used Werthamer-Helfand-Hohenberg (WHH) theory 30) was adopted here. According to the WHH theory, H c2 limited by the orbital depairing in the dirty limit is given by .…”