Researchers at BESSY II have, for the primary time, experimentally confirmed that a cloth can exhibit truly one-dimensional electronic properties. The team studied short chains of phosphorus atoms that naturally arrange themselves at specific angles on a silver surface. By applying advanced measurement and evaluation techniques, they separated the signals coming from chains aligned in several directions. This careful work showed that every individual chain behaves as a real one-dimensional electronic system.
The findings also point to a dramatic shift in behavior depending on how closely the chains are spaced. When the chains are farther apart, the fabric acts as a semiconductor. If packed tightly together, nevertheless, calculations predict it could behave like a metal.
From Two-Dimensional Materials to One Dimension
All materials are built from atoms that bond together in several patterns. In most solids, atoms connect each inside a plane and vertically. Some elements, reminiscent of carbon, can form graphene, a two dimensional (2D) hexagonal network during which atoms bond only inside a single layer. Phosphorus can also be able to forming stable 2D structures.
Two-dimensional materials have attracted intense interest due to their unusual electronic and optical properties. Theoretical studies suggest that shrinking materials down even further into one-dimensional structures could produce much more remarkable electro-optical effects.
Self-Assembled Phosphorus Chains on Silver
Under fastidiously controlled conditions, phosphorus atoms can organize themselves into short, straight lines on a silver substrate. Structurally, these lines appear one-dimensional. Nevertheless, neighboring chains should still interact with each other from the side. Those lateral interactions can alter the electronic structure and potentially disrupt true one-dimensional behavior. Until now, researchers had not been capable of clearly measure whether the electrons themselves were confined to a single dimension.
“Through a really thorough evaluation of measurements at BESSY II, we now 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.
Dr. Andrei Varykhalov and colleagues first created and examined the phosphorus chains using a cryogenic scanning tunnelling microscope (STM). The photographs revealed short phosphorus chains forming in three distinct directions across the silver surface, each separated by 120 degree angles.
ARPES Reveals True 1D Electronic Structure
“We achieved very high-quality results, enabling us to watch standing waves of electrons forming between the chains,” says Varykhalov. The team then mapped the electronic structure using angle-resolved photoelectron spectroscopy (ARPES) at BESSY II, a way during which they’ve extensive expertise.
Predicted Semiconductor-to-Metal Phase Transition
Dr. Maxim Krivenkov and Dr. Maryam Sajedi played a key role in interpreting the info. By fastidiously separating the contributions from the three in another way oriented chain domains, they were capable of isolate each chain’s electronic signature. “We could disentangle the ARPES signals from these domains and thus show that these 1D phosphorus chains actually possess a really distinct 1D electron structure too,” says Krivenkov.
Calculations based on density functional theory support the experimental results and suggest a very important shift because the chains move closer together. Stronger interactions between neighboring chains are predicted to trigger a phase transition from semiconductor to metal as chain density increases. In other words, if the chains form a tightly packed two-dimensional array, the fabric would behave as a metal.
“We’ve entered a brand new field of research here, uncharted territory where many exciting discoveries are more likely to be made,” says Varykhalov.