Printable two-dimensional superconducting monolayers

A mild electrochemical exfoliation method has been developed to obtain large-size two-dimensional superconductor monolayers with high crystallinity and production yield, which enables the easy fabrication of twisted van der Waals heterostructures and printed films. Two-dimensional superconductor (2DSC) monolayers with non-centrosymmetry exhibit unconventional Ising pair superconductivity and an enhanced upper critical field beyond the Pauli paramagnetic limit, driving intense research interest. However, they are often susceptible to structural disorder and environmental oxidation, which destroy electronic coherence and provide technical challenges in the creation of artificial van der Waals heterostructures (vdWHs) for devices. Herein, we report a general and scalable synthesis of highly crystalline 2DSC monolayers via a mild electrochemical exfoliation method using flexible organic ammonium cations solvated with neutral solvent molecules as co-intercalants. Using NbSe2 as a model system, we achieved a high yield (>75%) of large-sized single-crystal monolayers up to 300 mu m. The as-fabricated, twisted NbSe2 vdWHs demonstrate high stability, good interfacial properties and a critical current that is modulated by magnetic field when one flux quantum fits to an integer number of moire cells. Additionally, formulated 2DSC inks can be exploited to fabricate wafer-scale 2D superconducting wire arrays and three-dimensional superconducting composites with desirable morphologies.

Automated summary

A mild electrochemical exfoliation method has been developed to synthesize large-size, high crystallinity two-dimensional superconductor monolayers, enabling the fabrication of twisted van der Waals heterostructures and printed films. This method yields 2DSC monolayers with unconventional Ising pair superconductivity and enhanced upper critical field, with NbSe2 achieving a high yield of large single-crystal monolayers up to 300 μm. The resulting twisted NbSe2 vdWHs exhibit high stability, good interfacial properties, and modulation of critical current by magnetic field interaction.