High-pressure synthesis of micrometer single-atom copper chains

A research team based at the Center for High Pressure Science and Technology Advanced Research (HPSTAR) in Beijing reports that it has built copper wires only a single atom wide and more than a thousand atoms long — the longest continuous single-metal-atom chain ever made, and by a wide margin. The result, led by Kuo Li and published in the 20 August 2026 issue of Science, pushes a structure that physicists have chased for decades from a fragile laboratory curiosity into something that can be weighed, stored, and handled.

Why one-dimensional metal is so hard to keep

A single-metal-atom chain (SMAC) is the extreme end of miniaturisation: metal atoms lined up one after another in a straight line, with essentially no width. It is also a near-perfect testbed for one-dimensional condensed-matter physics — Peierls distortions, Tomonaga–Luttinger liquids, and spin chains all play out most cleanly when electrons are forced through a single atomic corridor. The trouble is that a row of atoms has almost no neighbours to hold it straight. In a bulk metal, each atom is braced from every side; in a chain, every atom has only a front and a back neighbour, so the structure easily rearranges itself into something lower in energy.

That fragility created a three-way trade-off that had defeated the field. One family of methods, such as assembling chains on a cold surface under ultrahigh vacuum, could produce clean, well-ordered chains — but only while the vacuum held, and only as short fragments. Solution-based chemistry had reached roughly two dozen atoms at most (about 28 nickel atoms, or ~10 nanometres, for the best reported record) and could not be scaled up. Approaches that gave stable, bulk quantities tended to deliver chains too short to study properly. Length, stability, and scalability refused to arrive together.

Locking the chain inside a carbon sleeve

Li's group sidestepped the trade-off with a strategy its members call high-pressure solid-state topological polymerisation. The starting material is beta-phase copper phthalocyanine (β-CuPc), the same blue pigment used in inks and plastics. In its crystal form, CuPc molecules stack in columns with the central copper ions already aligned along the stacking direction — a ready-made template for an atomic wire.

The team loaded the crystal into a Paris–Edinburgh press and squeezed it past 21 gigapascals (about 210,000 atmospheres). Detailed technical accounts of the work describe the intermolecular polymerisation beginning near 21.5 GPa and completing around 25 GPa with mild heating to roughly 533 K for about twelve hours. At that pressure the molecules are forced so close that their surrounding aromatic rings link up and polymerise into a dense, saturated carbon framework. That framework becomes a rigid sheath that grips the copper ions and holds them in a perfectly straight, evenly spaced line even after the pressure is released. Li describes it as slipping a protective sleeve over a thread that would otherwise snap.

The numbers are what make the work unusual. The carbon-sheathed crystals grew to roughly 940 × 250 × 50 micrometres — large enough to see and handle. After acid-assisted exfoliation, an individual copper chain stretches beyond one micrometre and connects more than 4,000 copper atoms in series, roughly two orders of magnitude longer than any previous sample. The copper–copper spacing is pinned at a tight 2.57 ångström, and the material was produced at milligram scale, meaning weighable, reusable quantities rather than a single microscope feature. The sheath also delivers the missing stability: the chains survive ambient pressure, strong acid, and aggressive ultrasonication.

What becomes measurable now

Because the chains are long, ordered, and durable, experiments that were previously impossible become practical. The Science paper reports anisotropic electrical conduction along the chain axis and one-dimensional antiferromagnetic coupling between neighbouring copper atoms, inferred from a combination of measurement and computation. A wire only one atom wide is a clean arena for asking whether a real material shows the exotic one-dimensional behaviours that theory has long predicted — and, just as importantly, for discovering where reality departs from the ideal chain.

From a remarkable material to a real interconnect (analysis)

It is tempting to read this as the dawn of atom-scale chip wiring, and the authors themselves note the long-term promise. Ho-kwang Mao, the CAS academician and high-pressure pioneer who co-authored the work, says atom-scale ultra-thin metal wires could offer a new material option for next-generation nanocircuits and flexible, wearable electronics. That is a plausible direction, not a near-term forecast.

【analysis】Reaching an actual device remains a different problem. Based on the reported results, several gaps stand between this material and a working interconnect, and treating them as solved would be premature. First, the chain lives inside a carbon sheath; using it as a conductor means making reliable electrical contact to a single atomic wire buried in an insulating tube, and doing so reproducibly across millions of devices. Second, the synthesis is a batch high-pressure process — turning milligram yields into uniform, addressable components on a wafer is an integration challenge of a different kind. Third, the electrical and magnetic properties reported are bulk and ensemble signatures; proving that an individual exfoliated chain behaves the same way, and at operating temperatures, is still ahead. None of this dims the result, but it is the difference between a breakthrough material and a shipped product. The honest reading is that the work removes a long-standing synthesis bottleneck and opens a physics platform; the engineering path from there is open, not short.

A route that may generalise

The method is not limited to copper. The team reports that the same high-pressure topological polymerisation extends to cobalt, nickel, zinc, and other metals, suggesting a general recipe for sheathed single-atom chains rather than a one-off. If that breadth holds up, the more important outcome may be the strategy itself: a way to "press" molecular precursors into atomically precise one-dimensional wires, opening a family of materials for both fundamental study and, eventually, the electronics of very small things.