Würzburg ToCoTronics Colloquium

Magic-angle twisted bilayer graphene (MATBG) hosts a rich phase diagram arising from the interplay of flat bands, electronic correlations, and topology. However, microscopic device details, including twist-angle inhomogeneity and strain, can produce substantial device-to-device variability, obscuring which features are universal and which are sample-specific.

In this talk, I will present recent advances in MATBG fabrication that improve twist-angle control and device homogeneity [1], together with a systematic transport study of 18 devices fabricated using the same protocol [2]. Comparison across the ensemble reveals two highly reproducible metallic states that are difficult to resolve in individual devices. In particular, we identify a dome-shaped metallic region directly above the superconducting domes. Its filling range, characteristic temperature scale, and magnetic-field response coincide with those of the ``outer gap'' recently observed spectroscopically, suggesting a common electronic origin.

Finally, I will discuss the potential of MATBG for quantum sensing, enabled by its low carrier density and ultralow electronic heat capacity [3]. In a proof-of-principle experiment, we use a voltage-biased MATBG device near its superconducting transition to detect individual infrared photons [4]. The absorption of a single photon triggers the breakdown of superconductivity, demonstrating the exceptional sensitivity of MATBG and its potential as a platform for moiré-based quantum sensing.

[1] J. Díez-Mérida et al., “High-yield fabrication of bubble-free magic-angle twisted bilayer graphene devices with high twist-angle homogeneity,” Newton 1, 100007 (2025).
[2] G. Di Battista et al., In preparation
[3] G. Di Battista et al., “Revealing the Thermal Properties of Superconducting Magic-Angle Twisted Bilayer Graphene,” Nano Letters 22, 6465–6470 (2022).
[4] G. Di Battista et al., “Infrared Single-Photon Detection with Superconducting Magic-Angle Twisted Bilayer Graphene,” Science Advances 10, eadp3725 (2024)