Strong enhancement of superconductivity in the topological transition metal silicide W5Si3 by Re doping

Abstract

We report the effect of Re doping in the prototype transition metal silicide W₅Si₃. Structural analysis shows that Re can substitute up to 20% of W in W₅Si₃ and its incorporation leads to an anisotropic shrinkage of the tetragonal lattice. T_c of W_5−xRe_xSi₃ is strongly enhanced with increasing Re content x from 2.45 K (x = 0) to 6.36 K (x = 1) and higher that of isostructural Mo_5−xRe_xSi₃ with the same valence electron count. This T_c enhancement is accompanied by a drastic increase in the upper critical field and attributed to the enhancement of electron–phonon coupling caused by doping-induced phonon softening. Theoretical calculations suggest that the electronic structure of undoped W₅Si₃ is characterized by strong Z₂ invariants (1;000) and this topological character is presumably preserved upon Re doping. Our study indicates that chemical doping provides a facile way to optimize superconductivity in topological transition metal silicides.