Robust Bulk Superconductivity by Giant Proximity Effect in Weyl Semimetal-superconducting NbP/NbSe2 Composites

We synthesize Weyl semimetal/superconductor NbP/NbSe2 composite and observe stable bulk superconductivity at Tc = 7.2 K, 6.9 K, and 6.8 K for NbSe2 crystal, NbP/NbSe2 (1:1), and NbP/NbSe2 (2:1) composites, respectively, despite large volume fraction of non-superconducting NbP phase. From the Ginzburg-Landau theory, the Hc2(0) is significantly enhanced in NbP/NbSe2 composites [22 T (1:1) and 18.5 T (2:1)] comparing with the pristine NbSe2 crystal (8 T). The bulk superconductivity in Weyl semimetal/superconductor composite cannot be simply described by the de Gennes-Meissner theory in a proximity effect. From the electrical transport, magnetization, and heat capacity measurement, we obtain various superconducting parameters. The superconducting properties indicate that the NbP/NbSe2 composite is far from the conventional BCS superconductivity. It suggests that the Weyl semimetal/superconductor composite can have giant proximity effect, resulting in the stable bulk superconductivity in a composite with sizable volume fraction of non-superconducting Weyl semimetals. The giant proximity effect in Weyl semimetal/superconductor interface can have a platform to investigate the proximity induced Weyl semimetallic superconducting states.

Exotic Superconducting States in Transition Metal Tellurides

Nb2Pd3Te5 was found to show bulk superconductivity at 3.3 K. In contrast, Ta2Pd3Te5, a 5d analogue of Nb2Pd3Te5, showed nonmetallic electronic conduction, which was changed to show bulk superconductivity by chemical doping.