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

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 W5-xRexSi3 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 Mo5-xRexSi3 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 Z(2) 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.