Periodic Reporting for period 3 - Programmable Matter (New materials enabled by programmable two-dimensional chemical reactions across van der Waals gap)
Reporting period: 2023-05-01 to 2024-10-31
Materials determine what our everyday world looks like and what technology is available to us. Progress in diverse industrial sectors, from heterogeneous catalysis to electronics microfabrication to energy storage applications, depends essentially on our ability to synthesise advanced materials. The last decade has seen the explosive advancement in 2D materials – hundreds of novel 2D materials have been synthesized, covering a wide range: metals, dielectrics, ferroelectrics, semiconductors, superconductors, magnets. Combining and engineering the physics and chemistry of atomic layers by van der Waals technology results in the creation of materials with previously inaccessible properties, leading to new physics that originates from both the intrinsic properties of 2D crystals and the synergy of interactions between them. Advances in 2D materials and van der Waals technology have generated new proof-of-principle devices, including flexible tunnel transistors, nanometre-thin light-emitting diodes, and ultra-sensitive photovoltaic sensors. Our group has been contributing to this exciting research field from the very early stages of its development. The accumulated knowledge on individual 2D materials, together with technological progress in van der Waals heterostructures, sets the big goal: new materials with bespoke properties, created on demand for the high-tech industry. This project will enable entirely new categories of materials, which impacts areas of advanced, nanoscale and functional materials, catalysis, materials for energy applications, for next-generation electronics, quantum, magnetic and spintronics technologies, among many others. By digitally addressing 2D chemistry, lateral heterojunctions and vertical heterostructures will be created, realising the direct synthesis of devices instead of individual materials. In a long run, this approach will lead to programmable matter, which changes its properties in response to programmed input or autonomous sensing.
During the first half of the project, our team:
1) built an experimental platform to perform and characterise 2D reactions. The system comprises the first-ever nano-FTIR sSNOM working in an inert environment (sub-ppb levels of O2 and H2O). This platform can find applications beyond the project, for instance, in the fields related to Li-batteries and fuel cells. Using the developed platform, we are now investigating the mechanisms of interactions between various 2D materials.
2) developed a range of novel methodologies, including in situ manipulation of van der Waals heterostructures for twistronics - our technique enables twisted 2D material systems in one single stack with dynamically tunable optical, mechanical, and electronic properties (Science Advances, 2021).
3) reported first-ever transport measurements on a metastable rhombohedral phase of graphite (Nature, 2020)
4) demonstrated a new type of fractal quantum Hall effect – a 2.5D Hofstadter’s butterfly, which paves the way towards 3D twistronics (Nature, 2023)
5) offered an exciting platform (twisted monolayer-bilayer graphene) with very flat electronic bands and strong correlations (Nature Physics, 2021).
6) contributed to the synthesis and exploration of gas permeation properties of organic quasi-2D membranes for future industrial applications (Nature Communications, 2022).
1) built an experimental platform to perform and characterise 2D reactions. The system comprises the first-ever nano-FTIR sSNOM working in an inert environment (sub-ppb levels of O2 and H2O). This platform can find applications beyond the project, for instance, in the fields related to Li-batteries and fuel cells. Using the developed platform, we are now investigating the mechanisms of interactions between various 2D materials.
2) developed a range of novel methodologies, including in situ manipulation of van der Waals heterostructures for twistronics - our technique enables twisted 2D material systems in one single stack with dynamically tunable optical, mechanical, and electronic properties (Science Advances, 2021).
3) reported first-ever transport measurements on a metastable rhombohedral phase of graphite (Nature, 2020)
4) demonstrated a new type of fractal quantum Hall effect – a 2.5D Hofstadter’s butterfly, which paves the way towards 3D twistronics (Nature, 2023)
5) offered an exciting platform (twisted monolayer-bilayer graphene) with very flat electronic bands and strong correlations (Nature Physics, 2021).
6) contributed to the synthesis and exploration of gas permeation properties of organic quasi-2D membranes for future industrial applications (Nature Communications, 2022).
We performed the first-ever transport measurements of rhombohedral graphite. We found that, in contrast to common hexagonal graphite, electrons in rhombohedral graphite strongly interact with each other, leading to electronic phase separation. Rhombohedral graphite opens up a is an entirely new playground to explore strong correlations, quantum criticality, and other exciting many-body phenomena that are usually reserved for materials composed of f- or d-elements.
We also expanded twistronics techniques to three-dimensional (3D) systems by exploring the effects of moiré superlattices in bulk graphite generated by crystallographic alignment with hexagonal boron nitride. Moiré superlattice results in doping-controlled multiple transitions of the topology of graphite surface states (reminiscent of a kaleidoscope with everchanging pictures as one rotates the lens). We found that moiré potential does not just modify the surface states of graphite but affects the electronic spectrum of the entire bulk of graphite. A fascinating result is the observation of a 2.5-dimensional mixing of the surface and bulk states in graphite, which manifests itself in a new type of fractal quantum Hall effect – a 2.5D Hofstadter’s butterfly. This work paves the way towards novel 3D twistronics.
We also expanded twistronics techniques to three-dimensional (3D) systems by exploring the effects of moiré superlattices in bulk graphite generated by crystallographic alignment with hexagonal boron nitride. Moiré superlattice results in doping-controlled multiple transitions of the topology of graphite surface states (reminiscent of a kaleidoscope with everchanging pictures as one rotates the lens). We found that moiré potential does not just modify the surface states of graphite but affects the electronic spectrum of the entire bulk of graphite. A fascinating result is the observation of a 2.5-dimensional mixing of the surface and bulk states in graphite, which manifests itself in a new type of fractal quantum Hall effect – a 2.5D Hofstadter’s butterfly. This work paves the way towards novel 3D twistronics.