Three-dimensional networks of superconducting NbSe2 flakes with nearly isotropic large upper critical field
Togo Takahashi, Chisato Ando, M. Saito, Yasumitsu Miyata, Yusuke Nakanishi, Jiang Pu, Taishi Takenobu
Abstract
Abstract Increasing the upper critical field H c2 in superconductors is one of the most significant requirements for superconducting applications. Two-dimensional (2D) noncentrosymmetric NbSe 2 is a promising candidate because its pair breaking is protected by the spin-momentum locking effect, resulting in a giant in-plane H c2 (~50 T). However, the strong anisotropy of 2D NbSe 2 suppresses the robustness of out-of-plane H c2 (<5 T). To overcome this issue, we propose a synthetic approach to produce superconducting NbSe 2 films with a nearly isotropic large H c2 . Scalable selenization methods are tailored to create 3D superconducting networks in which 2D NbSe 2 flakes are vertically aligned to the substrates. The angle-resolved magneto-transports reveal enhanced H c2 values that exceed 20 T for arbitrary directions under externally applied magnetic fields. The isotropic nature of H c2 is attributed to the averaging intrinsic anisotropy of NbSe 2 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.