Disordered nanocrystalline superconducting PbMo6S8 with a very large upper critical field.

Abstract

Large increases in the upper critical field B-C2(0) are reported in bulk superconductors that demonstrate another novel property for nanocrystalline materials. Disordered nanocrystalline PbMo6S8 superconductors were fabricated by mechanical milling and hot isostatic pressing. Conventional PbMo6S8 has B-C2(0)similar to50 T. The nanocrystalline materials have higher resistivity (rho(N)) and B-C2(0)similar to100 T. The disorder produced in these nanocrystalline materials is significantly different from that produced by doping because it increases rho(N) and, hence, B-C2(0) without significantly reducing the electronic density of states or superconducting transition temperature (T-C). Furthermore, the disorder reduces the electron mean-free path to similar to1 nm which is more than an order of magnitude smaller than the grain size and necessary to achieve the unprecedented increase in B-C2(0).