Three-dimensional networks of superconducting NbSe2 flakes with nearly isotropic large upper critical field

Increasing the upper critical field Hc2 in superconductors is one of the most significant requirements for superconducting applications. Two-dimensional (2D) noncentrosymmetric NbSe2 is a promising candidate because its pair breaking is protected by the spin-momentum locking effect, resulting in a giant in-plane Hc2 (~50 T). However, the strong anisotropy of 2D NbSe2 suppresses the robustness of out-of-plane Hc2 (<5 T). To overcome this issue, we propose a synthetic approach to produce superconducting NbSe2 films with a nearly isotropic large Hc2. Scalable selenization methods are tailored to create 3D superconducting networks in which 2D NbSe2 flakes are vertically aligned to the substrates. The angle-resolved magneto-transports reveal enhanced Hc2 values that exceed 20 T for arbitrary directions under externally applied magnetic fields. The isotropic nature of Hc2 is attributed to the averaging intrinsic anisotropy of NbSe2 through 3D structured films, which was determined by X-ray diffraction measurements. The proposed synthetic approach will provide a new method for creating practical superconductors that are robust against magnetic fields.

Temperature-programmed nitridation of monodispersed VOx nanoparticles into nanocrystalline superconducting oxygen-doped vanadium nitride

A two-stage synthesis process was employed to prepare high-quality nanocrystalline vanadium nitride (VN) for superconducting applications. Firstly, monodispersed amorphous VOx nanoparticles were obtained via thermal-decomposition of vanadium (III) acetylacetonate [V(acac)3]...

Effect of Isothermal on the Heat Treatment of Ag/Bi2212 Superconducting Tapes

Tapes of Ag/Bi2212 (Bi2Sr2CaCu2O8+δ) have been revealed as promising materials for superconducting applications at low temperatures (4.2 K using liquid helium or 20 K using a cryocooler) and high fields (above 10 T). The reaction and formation of phases are related to the ceramic densification and to the alignment of the grains, important for the improvement of the superconductor transport properties. In the present work, it is analyzed the influence of long isotherms at the temperature of 830 °C on the superconducting properties of Ag/Bi2212 samples. The heat treatments consisted of the use of two maximum temperatures of treatment (890 °C and 905 °C), with two different soaking times, both with an annealing isotherm at 830 °C for 5 h, 30 h, and 50 h.