Influence of nonmagnetic impurities on the upper critical field, critical current density, and vortex pinning mechanism of the noncentrosymmetric superconductor NbReSi

Abstract

The recently discovered noncentrosymmetric (NCS) rhenium-based superconductor, NbReSi, has been demonstrated to possess an enhanced upper critical field (Hc2) that approaches the Pauli-Clogston limit. In the regime of weak coupling, a high Hc2 (0) value offers an optimal framework for investigating the properties of vortex matter and its phase diagram in the parity-violated background. In this work, we present a comprehensive study on the resistivity, magnetization, and magnetoresistance behavior of NbReSi and the V-substituted Nb1−xVxReSi to derive their superconducting properties, including the lower and upper critical field, critical current density, flux pinning mechanisms, and the vortex phase diagram. The temperature dependence of Hc2 establishes the multiband characteristics with repulsive intraband and dominant interband coupling parameters, which is consistent with the s-wave pairing symmetry. Analyzing the ρ (T,H) behavior around the transition region via thermally activated flux flow of vortices unveiled the field-induced crossover from single vortex pinning to collective pinning. Moreover, such a field-induced transformation from δl-type pinning to δTc-type pinning was also noticed in all these samples. Additionally, the pinning force density and pinning parameters suggest the coexistence of both point core and surface pinning mechanisms based on the framework of the Dew-Hughes model. Most importantly, we find the estimated flux creep rate to be very slow (∼10−3) and comparable to other NCS superconductors, while the magnetic relaxation behavior implies a strong bulk vortex pinning in these systems. Finally, combining the parameters and results obtained from the analysis of resistivity, magnetization, and critical current density, we present the global phase diagram of NbReSi, which reflects a narrow vortex fluctuation region, an important characteristic for practical application.

Source-reported materials — not catalogue approval

Similar papers