Kekulé-ordered EU on SiC Creates Replica Dirac Bands with Gap Opening and Strong Exchange Coupling

Kekulé-ordered graphene represents a promising frontier in materials science, offering a platform to investigate novel quantum phenomena, and now, researchers have uncovered a dramatic effect within this material. Xiaodong Qiu, Tongshuai Zhu, and Zhenjie Fan, along with their colleagues, demonstrate a giant splitting of electronic bands in graphene achieved through the intercalation of europium atoms. This process, involving the precise arrangement of atoms within the graphene structure, folds and replicates the material’s characteristic electronic bands, creating new pathways for electron flow. Crucially, the team reveals a strong interaction between these electrons and the magnetic properties of the europium atoms, opening up exciting possibilities for spintronics and the development of advanced quantum technologies.

Europium Intercalation Alters Graphene’s Electronic Structure

Scientists are exploring a novel approach to modify graphene by inserting europium atoms between its layers. This intercalation process dramatically alters the arrangement of electrons within the graphene, influencing a bonding pattern known as Kekulé distortion and controlling how electrons move between different energy states. The ultimate goal is to engineer graphene’s electronic band structure, potentially creating materials with tailored properties for advanced applications. The research demonstrates that introducing europium induces a Kekulé distortion within the graphene lattice, significantly changing its electronic characteristics.

Crucially, the europium also controls how electrons scatter within the material, impacting their mobility and transport properties. The team observed variable hybridized band gaps, meaning the energy required to excite electrons can be tuned, suggesting the possibility of creating flat bands and strong correlation effects, potentially leading to exotic quantum phenomena. The team employed angle-resolved photoemission spectroscopy to map the electronic band structure and scanning tunneling microscopy to visualize the graphene lattice and observe the Kekulé distortion. Theoretical calculations complement these experimental results, providing a deeper understanding of the underlying physics. This research opens doors to creating new materials for electronics, architectures for quantum computing, and potentially even new superconducting materials, contributing to a broader understanding of strongly correlated electron systems.

Europium Intercalation Creates Ordered Graphene Superlattice

Scientists have developed a method to insert europium atoms between layers of graphene, creating a well-ordered structure with unique electronic properties. This process involves growing graphene on silicon carbide and carefully introducing europium atoms, resulting in a specific arrangement of europium atoms on the graphene surface, confirmed through reflection high-energy electron diffraction. Scanning tunneling microscopy revealed a clear height difference between regions with and without the intercalated europium, directly demonstrating the presence of the inserted atoms and confirming the formation of the ordered superlattice structure. Angle-resolved photoemission spectroscopy revealed that the introduction of europium folds the graphene’s electronic structure, creating new bands and significantly altering the material’s conductivity.

Detailed analysis of the data revealed a splitting of these folded bands, attributed to a strong interaction between electrons and the magnetic moments of the europium atoms. The team measured a Fermi velocity of 8. 1 × 10⁵ m/s and a gap opening of 0. 63 eV and 1. 55 eV, quantifying the impact of the europium intercalation. This method provides a pathway to engineer band splitting in graphene, potentially enabling applications in spintronics and quantum technologies.

Europium Intercalation Creates Kekulé-Ordered Graphene Structure

Scientists successfully inserted europium atoms between layers of graphene and a silicon carbide substrate, creating a novel material with remarkable electronic properties. This process results in a Kekulé-ordered structure, characterized by a specific arrangement of europium atoms on the graphene surface, confirmed through techniques like reflection high-energy electron diffraction and scanning tunneling microscopy. The introduction of europium dramatically alters the electronic band structure of the graphene, folding fundamental features known as Dirac cones from the corners to the centre of the material’s electronic structure. This folding creates replica Dirac bands and opens a gap in the electronic structure, significantly modifying the material’s conductivity.

Crucially, electrons within these replica bands exhibit a strong coupling with the magnetic moments of the europium atoms. This coupling manifests as a giant splitting of the folded bands, a phenomenon not observed in pristine graphene. Experiments demonstrate a Fermi velocity of 8. 1 × 10⁵ m/s and a band gap opening of 0. 63 eV and 1. 55 eV. The observed strong interaction between the replica bands and the europium atoms further confirms this interaction, paving the way for generating Dirac band splitting in graphene through Kekulé ordering, opening exciting possibilities for spintronics and quantum technologies.

Europium Intercalation Creates Folded Graphene Bands

This research demonstrates the successful creation of Kekulé-ordered graphene by inserting europium atoms between layers of graphene grown on silicon carbide. The team reveals that this Kekulé order induces a folding of the graphene’s electronic structure, specifically the Dirac cones, leading to the formation of new bands at the centre of the material’s electronic structure. More significantly, these folded bands exhibit a substantial splitting due to a strong interaction with the localised magnetic moments of the europium atoms. This interplay between the Kekulé order and the europium’s magnetism provides a novel method for modulating the behaviour of electrons within the graphene, extending beyond simple band folding, and suggests potential applications in spintronics and the exploration of unique physical properties relevant to quantum technologies. The authors acknowledge that simulating the observed interaction between the europium and graphene bands requires further refinement of their computational models. Future work may focus on optimising the material’s properties and exploring the potential for creating new quantum devices based on this unique combination of materials and electronic effects.