GRAPHENE WITH A TWIST

To push innovation in graphene and layered materials, we must understand their behaviour. Therefore, the Enabling Research Work Package focuses on understanding the most fundamental properties of these materials, exploring beyond the single one-atom-thick layer of graphene and venturing into new possibilities. Among these, we’re investigating twistronics – where different layered materials are stacked forming different angles, which results in properties like superconductivity. Moreover, we study the possibilities of layered materials in ferroelectric and magnetic devices, with applications in electronics.

THIS YEAR’S PROGRESS

In the field of twistronics, our focus has been to develop new ultra-high vacuum technologies to manufacture tailor-made heterostructures, always controlling the twist angle. We’re now preparing a patent for our innovative preparation protocols, which enable an unprecedented control of 0.2 degrees. Such precision will help our researchers discover new twisted combinations of graphene and layered materials, beyond the original ‘magic angle’ superlattice. Among other things, we’ve shown that twirled stacks of hexagonal boron nitride and transition metal dichalcogenides enable tuneable ferroelectric effects.
Another key advance in twistronics led us to the discovery of quantum anomalies in twisted bilayer graphene. These include states that range from Mott insulators to superconductors – and we’ve used these effects in devices such as electronic junctions. Besides preparing new materials, our Work Package has also developed new technologies to study them more efficiently, which is key to advance our understanding of layered materials. These include a totally new method for identifying atomically thin layers, as well as advances in scanning thermal microscopy to better study twisted bilayers, heterostructures and even combinations of layered materials with materials like polymers and semiconductors. We also explore the potential of graphene and layered materials to enable new functionalities in electronics, photonics and other technologies. That’s why we’re also interested in the magnetic properties of layered materials, which could lead to applications in data storage. Beyond the traditional materials, our Work Package has explored layered versions of manganese, cobalt and niobium sulfides, as well as chromium bromide. Some of these devices exhibit 100% magnetoresistance, opening new possibilities for sensors, navigation, hard drives and much more.

To further expand our knowledge, we also carry out computational modelling of properties like magnetism, charge density and superconductivity, and measure the effects of interlayer
coupling with tools like photoluminescence, infrared spectroscopy and Raman scattering. Combined, these strategies help us predict promising phenomena and better assess the potential of twisted heterostructures in real-life applications.

UPCOMING CHALLENGES

After developing innovative methods for the assembly of heterostructures – with or without a twist – the Enabling Research Work Package will focus on further refining this technology. We’ll improve homogeneity, cover larger areas and enhance our control of the twist angle beyond the state-of-the-art. In this line, another key milestone will include synthetic approaches ready for glove-box environments, which will democratise access to these innovative materials. In the future, we will further study the quantum and optical effects of twistronics in graphene bi- and tri-layers, as well as “sandwiches” with hexagonal boron nitride and other layered materials. Finally, in the next years of the Graphene Flagship project, we’ll aim to fully understand the relationships between charge transfer and magnetism in layered materials, particularly metal halides. In general, we’ll delve into anything that seems unexpected and interesting for the progress of the field.