Quantum Twisting Microscope images electrons in graphene

Weizmann Institute of Science researchers have reported the first direct images of interaction-reshaped flat bands in magic-angle twisted bilayer graphene, using a device called the quantum twisting microscope. The results were published in Nature last week, after first appearing on arXiv in June 2025. The paper says the measurements resolve a long-running puzzle in the field by showing that electrons in the material can look light in some parts of momentum space and heavy in others. The work centers on magic-angle graphene, a two-layer stack twisted by roughly 1.1 degrees, a system that has been studied for its links to superconductivity and correlated insulating states. ### What did the microscope actually see inside magic-angle graphene? The Nature paper says the team used quantum twisting microscopy to directly image the interacting energy bands of magic-angle twisted bilayer graphene with high momentum and energy resolution. According to the paper abstract and arXiv version, bands measured away from the magic angle tracked single-particle theory more closely, while bands at the magic angle were “completely transformed” by interactions. (nature.com) The arXiv abstract says those transformed bands showed “light and heavy electronic character at different parts of momentum space.” The authors wrote that doping then produced several effects, including bandwidth renormalization, “Mott-like cascades” in the heavy sector and “Dirac revivals” in the light sector. ### Why has that “light and heavy” language drawn attention? Nature’s research highlight on the paper said electrons in magic-angle graphene can behave as both heavy and light particles, depending on momentum. (nature.com) The paper itself ties that behavior to what the authors call the “dual nature” of the electrons. The authors wrote that the dual behavior does not come from two separate electronic states, but from electrons at different momenta within the same topological heavy-fermion-like flat bands. (arxiv.org) That point matters because earlier work in the field had left open whether different experiments were seeing different phases, rather than different parts of the same one. ### What is the quantum twisting microscope, and who built it? (nature.com) The quantum twisting microscope was introduced by researchers at the Weizmann Institute in a 2023 Nature paper. That paper described a microscope that uses a van der Waals tip and local interference experiments to probe quantum materials in ways conventional probes could not. A 2025 Weizmann news release on a cryogenic version of the instrument said the original room-temperature QTM had already imaged electronic spectra, and that the lower-temperature setup could also map phonons and electron-phonon coupling in twisted bilayer graphene. (arxiv.org) John Birkbeck, a lead author on that 2025 study, said the instrument could reveal how electrons interact with individual phonon modes. (nature.com) ### How does this fit with other recent QTM work? A March 26, 2026 LMU Munich release said an LMU-led team had become only the second group worldwide to realize a QTM. That group reported room-temperature measurements of electron-electron interactions in graphene after modifying the instrument with a hexagonal boron nitride tunneling layer. (eurekalert.org) The Weizmann-led magic-angle graphene paper is separate from that LMU work. The arXiv record lists J. Xiao, A. Inbar, John Birkbeck, N. Gershon, Y. Zamir, T. Taniguchi, K. Watanabe, Erez Berg and Shahal Ilani as authors, with Ilani as corresponding author at the Weizmann Institute. ### What does the paper say comes next? The authors reported a “persistent low-energy excitation tied to the heavy sector,” which they said suggests an unaccounted-for degree of freedom in the system. (lmu.de) The paper also says the results establish QTM as a tool for high-resolution spectroscopic studies of quantum materials that had been difficult to access with conventional techniques. Nature published the study as “Imaging the flat bands of magic-angle graphene reshaped by interactions,” and the earlier preprint remains available as arXiv:2506.20738. (arxiv.org) The named authors on those records include Xiao, Inbar, Birkbeck, Berg and Ilani, who are likely to be the primary participants in any follow-on experimental work using the same platform. (nature.com)