Researchers at BESSY II have experimentally verified that self-assembled phosphorus chains on a silver surface exhibit truly one-dimensional electronic properties. By separating signals from chains aligned in different directions, the team revealed each chain's distinct one-dimensional electron structure. The findings suggest that increasing chain density could shift the material from semiconductor to metal behavior.
Researchers at BESSY II, a synchrotron radiation facility, have for the first time experimentally confirmed that short chains of phosphorus atoms can host genuinely one-dimensional electronic behavior. These chains self-assemble on a silver substrate under controlled conditions, forming straight lines in three distinct directions separated by 120-degree angles. While the chains appear structurally one-dimensional, potential lateral interactions between neighboring chains had previously raised questions about their electronic properties.
To investigate, Dr. Andrei Varykhalov and colleagues used a cryogenic scanning tunneling microscope to create and image the phosphorus chains. They then employed angle-resolved photoelectron spectroscopy (ARPES) at BESSY II to map the electronic structure. "We achieved very high-quality results, enabling us to observe standing waves of electrons forming between the chains," says Varykhalov.
By carefully disentangling signals from the three differently oriented chain domains, Dr. Maxim Krivenkov and Dr. Maryam Sajedi isolated each chain's electronic signature. This analysis demonstrated that the electrons are confined to a single dimension within individual chains. "Through a very thorough evaluation of measurements at BESSY II, we have now shown that such phosphorus chains really do have a one-dimensional electronic structure," says Professor Oliver Rader, head of the Spin and Topology in Quantum Materials department at HZB.
Further, "We could disentangle the ARPES signals from these domains and thus demonstrate that these 1D phosphorus chains actually possess a very distinct 1D electron structure too," adds Krivenkov. Density functional theory calculations support these results and predict a phase transition: when chains are spaced farther apart, the material behaves as a semiconductor, but tighter packing into a two-dimensional array would make it metallic.
The study opens new avenues in materials science, particularly for one-dimensional structures derived from two-dimensional materials like phosphorene. "We have entered a new field of research here, uncharted territory where many exciting discoveries are likely to be made," says Varykhalov. The research appears in Small Structures (2025; 6(12)), DOI: 10.1002/sstr.202500458.