Electronic structure of superconducting Lu2Ni3Si5 and its reference compound Y2Ni3Si5 by ab initio calculations

Abstract

a b s t r a c tElectronic structures of orthorhombic ternary nickel silicides: superconducting Lu 2 Ni 3 Si 5 and its nonsuperconducting counterpart, Y 2 Ni 3 Si 5 , have been calculated employing the fully relativistic and fullpotential local-orbital method within the density functional theory. Our investigations were focused particularly on the band structures and Fermi surfaces (FSs), being very similar for both ternaries. It appears that their FSs exist in four bands and contain electronlike and holelike three-dimensional sheets and small pockets, which suggests a presence of two-or even multi-band superconductivity (SC) in Lu 2 Ni 3 Si 5 . The main difference between both systems is that only in Lu 2 Ni 3 Si 5 small electron FS pockets occur around the G point. It allows for arising BCS-like SC in this compound, as was deduced from previous heat-capacity measurements, while no sign of SC has been detected (at least down to 2 K) in Y 2 Ni 3 Si 5 . In the latter system, a possible formation of a ferromagnetic ground state, which usually tends to destroy SC, has been excluded by our calculations.

Electronic structure of the heavy-fermion superconductor Ce2Ni3Ge5 and its reference Ce2Ni3Si5 compound by ab initio calculations

“…In both investigated ternaries, the overall shape of the DOSs below EF is dominated by the Ni 3d electrons, similarly to their behavior in other nickel intermetallics, e.g. Lu2Ni3Si5 and Y2Ni3Si5 [17]. However, the centers of masses of these contributions for the Ge-and Si-based systems, being located at -2.0 and -2.5 eV, respectively, are shifted from each other by about 0.5 eV.…”

“…The discussion about the selection of the atomic positions in the 235-type ternary nickel silicides has been carried out elsewhere [17]. Here the u.c.…”

“…Because of the lack of experimental atomic positions for Ce2Ni3Si5, they were assumed as those in other rare-earth nickel silicide (Y2Ni3Si5 [8]). The discussion about the selection of the atomic positions in the 235-type ternary nickel silicides has been carried out elsewhere [17]. Here the u.c.…”

“…Only Y2Ni3Si5 [10] and a BCS-like superconductor Lu2Ni3Si5 [16] are paramagnets down to the lowest temperatures measured. The electronic structures of these ternaries were investigated by us earlier [17]. The non-superconducting Ce2Ni3Si5, possessing an open 4f-electron shell, has been chosen in this work as a better analogue to the considered here Ce2Ni3Ge5 superconductor than the above (Y;Lu)2Ni3Si5 systems.…”

The electronic structure of CeNiGe3 and YNiGe3 superconductors by ab initio calculations

“…Y 2 Ni 3 Si 5 with N(E F ) = 2.5 states/eV/f.u. [24]. It is worth to notice that in CeNiGe 3 , N(E F ) without the contributions of the Ce 4f electrons is almost equal to that in YNiGe 3 (see Fig.…”