Abstract
In the course of our search for unconventional superconductors amidst the 1:2:2 phases, we have re-investigated the LuTE2Si2 compounds with TE= Fe, Co, Ni, Ru, Pd and Pt. In this paper, we present the results of our fully relativistic ab initio calculations of the band structures, performed using the full-potential local-orbital code. The theoretical data are supplemented by the results of low-temperature electrical transport and specific heat measurements performed down to 0.35K. All the materials studied but LuPt2Si2 crystallize with the body–centered tetragonal ThCr2Si2–type structure (space group I4/mmm). Their Fermi surfaces exhibit a three-dimensional multi–band character. In turn, the Pt–bearing compound adopts the primitive tetragonal CaBe2Ge2–type structure (space group P4/nmm), and its Fermi surface consists of predominantly quasi–two–dimensional sheets. Bulk superconductivity was found only in LuPd2Si2 and LuPt2Si2 (independent of the structure type and dimensionality of the Fermi surface). The key superconducting characteristics indicate a fully-gapped BCS type character. Though the electronic structure of LuFe2Si2 closely resembles that of the unconventional superconductor YFe2Ge2, this Lu–based silicide exhibits neither superconductivity nor spin fluctuations at least down to 0.35K.
Published Version
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