Ultralong sheathed single-metal-atom chains synthesized under high pressure.

Single-metal-atom chains (SMACs) represent the ultimate limit of one-dimensional nanostructures. They serve as archetypal model systems for condensed matter physics and constitute fundamental building blocks for next-generation nanoelectronics. However, synthesis of SMACs suitable for practical applications remains challenging. In this work, we create micrometer-long, carbon-sheathed copper SMACs at milligram scale by compressing β-copper phthalocyanine to above 21 gigapascals. The SMACs are in atom-scale ordering, are isolable through acid-assisted exfoliation, and exhibit exceptional stability, with Cu-Cu distance confined at 2.57 angstroms. Anisotropic conductance and antiferromagnetic interactions are suggested by experimental and computational results. This work establishes a universal synthetic strategy for sheathed SMACs, positioning them as a compelling platform for prospective electronic and spintronic applications.