Superconductivity in electrochemical exfoliated NbSe₂ atomic layers

Monolayer NbSe₂ with non-centrosymmetric lattice exhibit unconventional Ising superconductivity where the spin of electrons is locked along out-of-plane direction by spin-orbital interaction, which drives intense research interest. However, it is challenging to use mechanical exfoliation to fabricate a van der Waals heterostructure with  monolayer due to the low yield percentage of large-sized monolayers and environmental oxidation. Herein, we use a mild electrochemical exfoliation method to fabricate NbSe₂ devices achieving high yield of large-sized single-crystal monolayers with high stability. In the as-fabricated twisted NbSe₂ devices, we observed that the critical current shows oscillating behavior with the magnetic field. It is reminiscent of the effect of a magnetic field on a frustrated Josephson junction array with triangular symmetry, which is realized in the twisted devices with moiré pattern.