Researchers from Ludwig-Maximilians-Universität München (LMU Munich), Princeton University, Peking University, University of Florida, Basque Foundation for Science, Technical University of Munich, and Japan's National Institute of Material Sciences have built an advanced Quantum Twisting Microscope (QTM) that can observe, with unprecedented precision, the interactions between electrons in graphene - even at room temperature. The study, led by Professor Dmitri Efetov from LMU’s Faculty of Physics and co-coordinator of the Munich Center for Quantum Science and Technology (MCQST), marks a major leap forward in the direct measurement of quantum many-body effects in two-dimensional (2D) materials.
Quantum Twisting Microscope in Munich. Image credit: MCQST
At its core, the QTM enables energy- and momentum-resolved tunneling spectroscopy between two atomically thin layers with a controllable twist angle. By integrating a hexagonal boron nitride (hBN) layer as a tunneling dielectric, the team significantly improved both the energy resolution and the operational range of twist angles. This enhancement allowed researchers to access previously hidden dispersion features in tunneling spectra between two monolayer graphene sheets. The measurements revealed a logarithmic correction to graphene’s linear Dirac spectrum, a hallmark of electron-electron interactions long predicted but never before observed under ambient conditions. The extracted fine-structure constant, α ≈ 0.32 ± 0.01, quantifies the interaction strength and aligns closely with theoretical expectations.
What makes this result particularly interesting is that these subtle many-body corrections are resolved at room temperature, where thermal effects usually overwhelm delicate quantum signatures. The quantum twisting microscope achieves this extraordinary sensitivity through interferometric interlayer tunneling, which amplifies even minute band-structure modifications arising from electronic correlations.
Beyond confirming a decades-old theoretical prediction, the work highlights the robustness of electron-electron interactions in nonordered graphene states and demonstrates the QTM’s capacity to probe spectral functions and excitations in both twisted and untwisted 2D systems. Because the twist angle can be tuned in situ with high precision, the instrument can track the continuous evolution of electronic structure - a major advantage over conventional fixed-angle moiré devices.
With its combination of precision, flexibility, and analytical power, the enhanced QTM is poised to become a cornerstone tool for exploring correlated quantum phenomena in van der Waals heterostructures. The technique opens new opportunities to study superconductivity, magnetism, and other emergent behaviors across the rapidly growing landscape of moiré quantum materials.
