Aza-triangulene Architectures Engineer Frustrated Antiferromagnetic Triradicals for Scalable Spin-Based Quantum Architectures
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Open-shell nanographenes represent a promising avenue for developing new spin-based technologies, and researchers are increasingly focused on creating molecular systems that host unconventional magnetic states. Francisco Romero-Lara, Manuel Vilas-Varela, and Ricardo Ortiz, alongside Manish Kumar, Alessio Vegliante, and Lucía Gómez-Rodrigo, have now demonstrated a strategy to engineer a frustrated antiferromagnetic triradical within aza-triangulene architectures.
The team successfully reconfigured a single-radical molecule by extending it with anthene moieties, inducing a transition to a system exhibiting correlated spins and a unique magnetic configuration. This achievement represents a significant step towards creating molecular analogues of multi-qubit quantum registers, potentially offering a scalable route for advanced quantum computing applications. Nitrogen Doping and Graphene Edge States Scientists investigated the electronic and magnetic properties of graphene nanoribbons, focusing on those with unique edge states and incorporating nitrogen atoms into their structure. They employed sophisticated computational methods, including density functional theory and multireference configuration interaction, to accurately describe the behaviour of electrons within these materials, essential for understanding systems with unpaired electrons and strong interactions.
The team also used natural transition orbital analysis to visualize the complex electronic structure and scanning tunneling microscopy simulations to predict how these materials would appear under experimental observation. By introducing nitrogen atoms, scientists modify the electronic properties and induce magnetism within the graphene structure, revealing the magnetic ground states and the possibility of spin-polarized arrangements. Aza-triangulene Synthesis and Surface Nanostructure Formation Researchers developed a new method for creating and studying extended aza-triangulene platforms, beginning with chemical reactions in solution. They reacted specific molecules and used Friedel-Crafts cyclization to form precursor structures, which were deposited onto a gold surface and heated to induce chemical transformations, ultimately yielding the desired planar nanostructures. Bond-resolved atomic force microscopy and scanning tunneling microscopy confirmed the successful formation of both aza-triangulene and related molecules.
The team used low-bias tunneling spectroscopy to investigate the magnetic properties of the molecules at their zigzag edges, observing narrow peaks in the spectra attributed to the Kondo effect, where unpaired electrons interact with the surrounding environment. Measurements under applied magnetic fields revealed a spin-1/2 ground state, and detailed maps of the electron density showed that the Kondo effect is delocalized across the entire molecular platform, supported by theoretical simulations. Aza-Triangulenes Exhibit Kondo Resonance and Conductivity Scientists successfully synthesized and characterized extended aza-triangulene and benz-aza-triangulene platforms on a gold surface, demonstrating a pathway to create nanographenes with tailored electronic and magnetic properties. The synthesis involved solution-phase reactions followed by on-surface dehydrogenation, confirmed through advanced microscopy techniques, revealing the honeycomb lattice structure and enhanced current signals at the zigzag edges, indicating increased electron density. Low-bias tunneling spectroscopy revealed narrow peaks in the spectra of both molecules, assigned to Kondo resonances resulting from the screening of unpaired electrons by the substrate. Measurements under applied magnetic fields confirmed a spin-1/2 ground state, and the Kondo resonances were spatially delocalized across the entire molecular platform, accurately reproduced by theoretical simulations. Aza-triangulene exhibited additional features in its spectra, attributed to inelastic spin excitations, and multi-reference quantum chemistry simulations confirmed its multiradical character, capturing the spin distribution in the ground state. Key findings include narrow zero-bias peaks indicating Kondo screening of unpaired electrons, with Kondo temperatures of approximately 3 K. Application of a magnetic field broadened the peaks, characteristic of Kondo-screened spin-1/2 ground states, and the low-energy spectrum of aza-triangulene exhibited features at approximately ±100mV, attributed to inelastic spin excitations. Aza-Triangulene Becomes a Molecular Triradical System Researchers have successfully redesigned an aza-triangulene molecule, transforming it from a single radical into a frustrated triradical system. This achievement involved attaching specific molecular segments to the molecule’s edges, increasing the number of unpaired electrons and creating weakly coupled spins, resulting in a system analogous to a three-qubit quantum register. This work demonstrates a novel approach to controlling magnetic interactions at the molecular level, leveraging nitrogen substitution within the aza-triangulene core to reverse exchange patterns. By uniting chemical synthesis with concepts of spin frustration and topological protection, the team established a general design principle for creating molecular platforms with symmetry-protected, weakly coupled spins, offering a chemically programmable foundation for quantum registers. Future research will focus on optimizing the molecular segment length and exploring different substitution patterns to enhance spin coherence and control. 👉 More information 🗞 Topological Engineering of a Frustrated Antiferromagnetic Triradical in Aza-Triangulene Architectures 🧠 ArXiv: https://arxiv.org/abs/2512.10869 Tags: