Exploring Quantum Geometry with Terahertz Light: A Breakthrough in Twisted Bilayer Graphene

A recent groundbreaking study led by ICFO researchers, in collaboration with several international research groups including memebrs of the Aachen Graphene & 2D Materials Center, has uncovered previously unseen behaviors in magic-angle twisted bilayer graphene using terahertz light. As part of this international effort, the research sheds new light on the quantum geometry of this enigmatic material, revealing how the electronic wavefunctions of electrons are shaped by their environment.

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A scalable method to reduce the contact resistance of graphene

The exceptional electronic properties of graphene make it a material with large potential for low-power, high-frequency electronics. However, the performance of a graphene-based device depends not only on the properties of the graphene itself, but also on the quality of its metal contacts. The lack of effective and manufacturable approaches to establish good ohmic contacts to a graphene sheet is one of the factors that limit today the full application potential of graphene technology.

(a–d) Schematics showing the process sequence for manufacturing the devices and the laser irradiation of graphene in the contact regions. (e) Optical micrograph of one of the measured devices
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A non-destructive way to probe inter-layer coupling on millimeter-scale graphene-MoS2 heterostructures

One of the great assets of two-dimensional (2D) materials is the possibility of placing different materials on top of each other to form heterostructures with properties tailored to specific application scenarios. However, the quality of the final material stack strongly depends on the electronic coupling between the different materials. Measuring this coupling in a non-destructive way is therefore an important aspect for material development. Researchers from AMO GmbH, RWTH Aachen University and AIXTRON SE have now established a methodology based on Raman spectroscopy for estimating quantitatively the coupling between graphene and molybdenum disulfide (MoS2) in heterostructures up to the mm2-scale.

Graphical summary of the work of Nico Rademacher and co-workers (From: Micro and nano Engineering, https://doi.org/10.1016/j.mne.2024.100256)
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