Tiny, individual, flexible ribbons of crystalline phosphorus discovered by UCL researchers in 2019 exhibit magnetic and semiconducting properties at room temperature, opening new possibilities for next-generation electronics, finds a new study involving members of the same team.
The findings, published in the journal Nature, confirm the one-atom-thick ribbons, known as phosphorene nanoribbons, as a unique class of material that could enable more energy-efficient computing and unlock new quantum technologies.
The researchers demonstrated that the ribbons had remarkable, macroscopic magnetic properties at room temperature. When in thin films, the ribbons displayed magnetic behaviour akin only to that of classic magnetic metals such as iron and nickel.
These properties open new possibilities for electronic circuits, where magnetic properties could be used to manipulate the electronic states in a low-energy way. This could also lead to faster storage devices where light is used to switch the magnetic state.
The ability to align nanoribbons using weak magnetic fields in solution is also a new way to control nanomaterials. This could lead to scalable fabrication techniques for quantum devices, flexible electronics, and next-generation transistors.
The study was led by the University of Cambridge in collaboration with teams from UCL, the University of Warwick, Freie Universität Berlin and the European High Magnetic Field lab in Nijmegen.
Co-author Professor Chris Howard (UCL Physics & Astronomy), whose team discovered phosphorene nanoribbons, said: "There are many theoretical predictions of exciting properties for phosphorene nanoribbons that we looked forward to searching for when we discovered how to make them. The possibility that they are a unique material that is intrinsically both a semiconductor and magnetic was right at the top of this list. It's been absolutely fascinating studying these properties and their interplay."
The UCL team, working with researchers at other institutions, have already shown that phosphorene nanoribbons could be alloyed with arsenic, modifying their properties, and also that the nanoribbons could improve the efficiency of solar cells."
Professor Howard added: "Exploring the myriad of extraordinary properties these materials are exhibiting has opened up some extremely rewarding collaborations."
Arjun Ashoka, of the University of Cambridge, who is first author of the new paper, said: "We discovered that in addition to their magnetic properties, phosphorene nanoribbons host excited states on the magnetic edge of the nanoribbon, where it interacts with atomic vibrations (phonons) that are normally not allowed by the material's bulk symmetries.
"This unusual interaction allows phosphorene nanoribbons to uniquely couple magnetic, optical and vibrational properties on its one-dimensional edge.
"For years we've explored and utilised the devilish yet benevolent 2D surfaces of 3D materials, from catalysis to device physics. With these new nanoribbons we've hopefully unlocked access to new physics on the 1-dimensional analogue of a 2D surface: an edge."
This work is particularly significant as it marks the first experimental validations of the predicted, but difficult to observe magnetic properties of phosphorene nanoribbons.
Corresponding author Dr Raj Pandya, formerly of the University of Cambridge and now at the University of Warwick, said: "The best thing about this work, apart from being a really exciting finding, has been the great team we have worked with over 10 institutes and five years, highlighting the amazing science that can be done when we work together."
The next steps of the research involve finding ways to study the coupling of magnetism with light and vibrations on the edge of these ribbons and exploring their potential to develop entirely new device concepts.
