A comparative study of doping effects of V and Cr on a SrAlSi superconductor

Abstract

It is well known that the superconducting transition temperature (T_c) is very sensitive to the electronic density of states at the Fermi energy (N(E_F)) and the Debye frequency (Θ_D) for a BCS superconductor. However, which one plays a leading role in the ternary silicides AeMSi (Ae = Ca/Sr/Ba and M = Al/Ga) system is still unclear. Here, we report a comparative study of doping effects by V and Cr at Al sites in SrAlSi, which has a relatively high T_c among AeMSi systems. It is found that V and Cr atoms can be successfully introduced into SrAlSi with the actual solid solution limit up to 16 at% and 13 at%, respectively. In this case, the incorporation of V and Cr will have nearly identical effects in decreasing Θ_D. Hall effect measurements demonstrate that V and Cr have dramatically different effects on the carrier concentration upon doping. In SrAl_1−xV_xSi, the carrier concentration is decreased by about three orders of magnitude and V dopants lead to the quenching of superconductivity at the highest doping level. In contrast, Cr almost does not change the carrier concentration, leading to a minor change in T^onset_c of 0.6 K. Our results provide solid evidence that the N(E_F) should be responsible for the T_c in the transition metal doped AeMSi system.