Periodic Reporting for period 1 - QTM (The Quantum Twisting Microscope - revolutionizing quantum matter imaging)
Reporting period: 2023-04-01 to 2025-09-30
The project aims to develop the Quantum Twisting Microscope (QTM), an innovative scanning probe microscope designed to directly image electronic wavefunctions and energy bands within quantum materials. At its core lies a unique tip composed of an atomically thin van der Waals material, which functions as a quantum interferometer. Electrons tunnel from this tip into a sample at multiple locations at once, and the quantum interference between these tunneling paths enables the measurement of the phase evolution within electronic wavefunctions. These measurements allow the QTM to probe electrons in momentum space, much as a scanning tunneling microscope probes electrons in real space. We will use this novel microscope to realize highly tunable twisted interfaces and explore their phase diagrams. In addition, we will measure in a large variety of quantum material fundamental properties of their electrons, which were so far largely inaccessible. This will include their electronic and collective mode spectra, as well as their potential landscapes. These experiments aim to transform our understanding of quantum matter in twisted atomic interfaces.
Over the first two years, the QTM project has delivered a series of landmark breakthroughs that firmly establish quantum-twisting spectroscopy as a transformative technique in quantum-matter imaging:
• Next-generation instruments: We conceived, built and commissioned several generations of Quantum Twisting Microscopes, with increasing complexity:
• A room-temperature system based on a modified commercial AFM.
• A custom cryogenic microscope operating at 4 K.
• The most advanced QTM working at millikelvin temperatures.
• A fourth, cryo-free QTM in an AttoDry 2200 platform is under construction.
• Quantum twisting microscopy of phonons in twisted bilayer graphene: We pioneered the use of QTM to map phonon dispersions and mode-resolved electron–phonon coupling in TBG, discovering a low-energy phason mode that plays a critical role in moiré-mediated interactions. This capability bridges the gap between spectroscopy and microscopy, offering an unprecedented window into many-body physics. (Nature 641, 345–351 (2025)).
• Theory of phonon spectroscopy with the quantum twisting microscope: We provided the first closed-form framework for both elastic and inelastic momentum-conserving tunneling currents. It delivers practical protocols to extract quantitative electron and phonon spectral functions directly from QTM measurements. (PRB 110, 205407 (2024)).
• Theory of Probing quantum spin liquids with the QTM: We introduced a theoretical scheme showing how QTM can detect fractionalized spinon continua in candidate spin-liquid materials by measuring their unique inelastic momentum signatures, opening a new route to characterize these elusive phases. (PRB 035127 (2024)).
• Imaging the Sub-Moiré Potential Landscape using an Atomic Single Electron Transistor: By harnessing a single-atom defect on a QTM tip as an ultrasensitive transistor, we achieved electrostatic potential maps in graphene/hBN with two orders of magnitude finer spatial resolution than previous techniques. This provided the first images of sub-moiré potential within this system, with surprising findings which have a crucial impact on the field of moire systems. This work is in advanced stages of review in Nature.
• First images of the interacting energy bands of magic angle graphehe: We provided the first visualization of interacting energy bands in magic-angle graphene at cryogenic temperatures, resolving the long-standing puzzle of why electrons behave simultaneously as localized and extended. This advance is a crucial step toward unraveling the mechanisms of correlated superconductivity in moiré systems. This work is under review in Nature.
• Global outreach: These scientific advances have been showcased in 26 invited talks at premier international venues, maximizing the project’s visibility and fostering new collaborations. These include distinguished public talks such as the 2025 Bethe public lecture at Cornell University or the Orsted talk in DTU.
• Next-generation instruments: We conceived, built and commissioned several generations of Quantum Twisting Microscopes, with increasing complexity:
• A room-temperature system based on a modified commercial AFM.
• A custom cryogenic microscope operating at 4 K.
• The most advanced QTM working at millikelvin temperatures.
• A fourth, cryo-free QTM in an AttoDry 2200 platform is under construction.
• Quantum twisting microscopy of phonons in twisted bilayer graphene: We pioneered the use of QTM to map phonon dispersions and mode-resolved electron–phonon coupling in TBG, discovering a low-energy phason mode that plays a critical role in moiré-mediated interactions. This capability bridges the gap between spectroscopy and microscopy, offering an unprecedented window into many-body physics. (Nature 641, 345–351 (2025)).
• Theory of phonon spectroscopy with the quantum twisting microscope: We provided the first closed-form framework for both elastic and inelastic momentum-conserving tunneling currents. It delivers practical protocols to extract quantitative electron and phonon spectral functions directly from QTM measurements. (PRB 110, 205407 (2024)).
• Theory of Probing quantum spin liquids with the QTM: We introduced a theoretical scheme showing how QTM can detect fractionalized spinon continua in candidate spin-liquid materials by measuring their unique inelastic momentum signatures, opening a new route to characterize these elusive phases. (PRB 035127 (2024)).
• Imaging the Sub-Moiré Potential Landscape using an Atomic Single Electron Transistor: By harnessing a single-atom defect on a QTM tip as an ultrasensitive transistor, we achieved electrostatic potential maps in graphene/hBN with two orders of magnitude finer spatial resolution than previous techniques. This provided the first images of sub-moiré potential within this system, with surprising findings which have a crucial impact on the field of moire systems. This work is in advanced stages of review in Nature.
• First images of the interacting energy bands of magic angle graphehe: We provided the first visualization of interacting energy bands in magic-angle graphene at cryogenic temperatures, resolving the long-standing puzzle of why electrons behave simultaneously as localized and extended. This advance is a crucial step toward unraveling the mechanisms of correlated superconductivity in moiré systems. This work is under review in Nature.
• Global outreach: These scientific advances have been showcased in 26 invited talks at premier international venues, maximizing the project’s visibility and fostering new collaborations. These include distinguished public talks such as the 2025 Bethe public lecture at Cornell University or the Orsted talk in DTU.
Both the technical and scientific achievements listed above go way beyond the state of the art. We have build a cascade of conceptually new experimental machines that have not existed yet. Using these machines we have made a series of groundbreaking scientific discoveries, each of which goes well beyond the state of the art.