Research Interests

My research uses quantum transport — and, increasingly, nanophotonic and photocurrent probes — to uncover emergent phenomena in low-dimensional quantum materials. Graphene and van der Waals heterostructures are the platform of choice: the ability to stack crystalline layers free from lattice-matching constraints, and to control the twist angle between them, gives unparalleled tunability of band structure, interaction strength, and topology. My group at MPI Stuttgart investigates three interconnected themes.

General Reading:
  • Electronic transport in two-dimensional graphene, Rev. Mod. Phys. 83, 407 (2011) [arXiv:1003.4731] [DOI]
  • Van der Waals heterostructures, Nature 499, 419–425 (2013) [arXiv:1307.6718] [DOI]
  • Moiré nano-optoelectronics, 2D Materials 13, 021501 (2026) [DOI]

Quantum transport in low-dimensional materials

One of the central contributions of my research has been the realisation of a strictly one-dimensional (1D) electronic system, where electrons are confined to domain-wall channels in Bernal bilayer graphene. Theory has long predicted that 1D metallic systems are unstable and that superconductivity in one dimension is forbidden by quantum fluctuations. Our experiments challenged this picture by demonstrating proximity-induced superconductivity in the quantum Hall regime, with a transparency approaching the theoretical conductance limit and far exceeding any previously known 1D system. This platform opens routes to addressing long-standing questions in 1D physics — from Luttinger liquid behaviour to topological superconductivity — for which clean, controllable systems were previously unavailable.

More broadly, I have introduced Brown-Zak fermions: a family of quasiparticles that emerge in moiré superlattices at rational fractions of the magnetic flux per unit cell and propagate ballistically despite large applied fields.

Recent articles on the topic:
  1. One-Dimensional Proximity Superconductivity in the Quantum Hall Regime, Nature 628, 741 (2024). [arXiv:2402.14451] [DOI] [PDF]
  2. Long-Range Ballistic Transport of Brown-Zak Fermions in Graphene Superlattices, Nature Communications 11, 5756 (2020). [arXiv:2006.15040] [DOI] [PDF] [SI]

Electron–electron interactions

The textbook picture of non-interacting electrons breaks down in the presence of strong Coulomb repulsion, giving rise to collective many-body phenomena that are notoriously difficult to predict. One of the key methodological contributions of my group is the development of van der Waals heterostructure-based screening techniques, enabling sub-nanometer control of the dielectric environment and thus continuous, in-situ tuning of interaction strength — turning Coulomb screening into a quantitative experimental knob.

We have uncovered correlated phases across a broad class of systems: electronic phase separation with multiferroic-like hysteresis in rhombohedral graphene, electrostatically tuneable van Hove singularities and continuously evolving correlated states in twisted monolayer-bilayer graphene, and the role of screening in the pairing mechanism of unconventional superconductivity in magic-angle twisted bilayer graphene. Even in ostensibly simple systems, interactions reveal unexpected physics: monolayer graphene hosts a strongly interacting electron-hole Dirac plasma at low carrier density that produces giant magnetoresistance. Together, these results establish interaction tuning as a unifying experimental strategy for mapping the phase diagrams of correlated quantum materials.

Recent articles on the topic:
  1. Coulomb Screening of Superconductivity in Magic-Angle Twisted Bilayer Graphene, (2025). [arXiv:2412.01577] [DOI]
  2. Proximity Screening Greatly Enhances Electronic Quality of Graphene, Nature 644, 646 (2025). [arXiv:2507.21997] [DOI]
  3. Giant Magnetoresistance of Dirac Plasma in High-Mobility Graphene, Nature 616, 270 (2023). [arXiv:2302.06863] [DOI]
  4. Electronic Phase Separation in Multilayer Rhombohedral Graphite, Nature 584, 210 (2020). [arXiv:1911.04565] [DOI]

Nanophotonic probes

Complementing low-frequency transport, my group develops nanophotonic and photocurrent techniques to access physical observables invisible to conventional electrical measurements. Using IR and THz experiments, we demonstrated that magic-angle twisted bilayer graphene hosts spontaneous inversion symmetry-breaking correlated states whose polarisation axes rotate sharply with interaction strength — a signature invisible to dc transport. We used optical spectroscopy to map the formation of moiré minibands near the magic angle, while polarisation-resolved photocurrent measurements in bilayer graphene superlattices enabled single-photon detection via negative differential conductance.

Near-field techniques further allow direct mapping and characterisation of two-dimensional systems at the nanoscale, opening new routes to probing quantum geometry and non-equilibrium dynamics.

Recent articles on the topic:
  1. Single-Photon Detection Enabled by Negative Differential Conductivity in Moiré Superlattices, Science 389, 644 (2025). [arXiv:2505.13637] [DOI]
  2. Terahertz Photocurrent Probe of Quantum Geometry and Interactions In Magic-Angle Twisted Bilayer Graphene, Nature Materials 1034 (2025). [arXiv:2406.16532] [DOI]
  3. Infrared Spectroscopy for Diagnosing Superlattice Minibands In Magic-Angle Twisted Bilayer Graphene, Nano Lett. (2024). [arXiv:2404.05716] [DOI]