> Abstract: Magic-angle twisted multilayer graphene stands out as a highly tunable class of moiré materials that exhibit strong electronic correlations and robust superconductivity [1,2,3,4]. However, understanding the relationships between the low-temperature superconducting phase and the preceding correlated parent states remains a challenge. Here we use scanning tunnelling microscopy (STM) and spectroscopy to track the formation sequence of correlated phases established by the interplay of dynamic correlations, intervalley coherence and superconductivity in magic-angle twisted trilayer graphene (MATTG). We discover the existence of two well-resolved gaps pinned at the Fermi level within the superconducting doping range. Although the outer gap, previously associated with the pseudogap phase [5,6], persists at high temperatures and magnetic fields, the newly revealed inner gap is more fragile, in line with previous transport experiments [1,2,4]. Andreev reflection spectroscopy taken at the same location confirms a clear trend that closely follows the doping behaviour of the inner gap and not the outer one. Moreover, spectroscopy taken at nanoscale domain boundaries further corroborates the contrasting behaviour of the two gaps, with the inner gap remaining resilient to structural variations. By comparing our results with recent topological heavy fermion (THF) models that include dynamical correlations [7,8], we find that the outer gap probably arises from a splitting of the Abrikosov–Suhl–Kondo resonance [9,10] owing to the breaking of the valley symmetry. Our results indicate an intricate yet tractable hierarchy of correlated phases in twisted multilayer graphene.
> Using a nanoscale scanning magnetometer, we imaged a distinctive hydrodynamic transport pattern—stationary current vortices—in a monolayer graphene device at room temperature. By measuring devices with increasing characteristic size, we observed the disappearance of the current vortex and thus verified a prediction of the hydrodynamic model. We further observed that vortex flow is present for both hole- and electron-dominated transport regimes but disappears in the ambipolar regime. We attribute this effect to a reduction of the vorticity diffusion length near charge neutrality. Our work showcases the power of local imaging techniques for unveiling exotic mesoscopic transport phenomena.
westurner•2h ago
> Abstract: Magic-angle twisted multilayer graphene stands out as a highly tunable class of moiré materials that exhibit strong electronic correlations and robust superconductivity [1,2,3,4]. However, understanding the relationships between the low-temperature superconducting phase and the preceding correlated parent states remains a challenge. Here we use scanning tunnelling microscopy (STM) and spectroscopy to track the formation sequence of correlated phases established by the interplay of dynamic correlations, intervalley coherence and superconductivity in magic-angle twisted trilayer graphene (MATTG). We discover the existence of two well-resolved gaps pinned at the Fermi level within the superconducting doping range. Although the outer gap, previously associated with the pseudogap phase [5,6], persists at high temperatures and magnetic fields, the newly revealed inner gap is more fragile, in line with previous transport experiments [1,2,4]. Andreev reflection spectroscopy taken at the same location confirms a clear trend that closely follows the doping behaviour of the inner gap and not the outer one. Moreover, spectroscopy taken at nanoscale domain boundaries further corroborates the contrasting behaviour of the two gaps, with the inner gap remaining resilient to structural variations. By comparing our results with recent topological heavy fermion (THF) models that include dynamical correlations [7,8], we find that the outer gap probably arises from a splitting of the Abrikosov–Suhl–Kondo resonance [9,10] owing to the breaking of the valley symmetry. Our results indicate an intricate yet tractable hierarchy of correlated phases in twisted multilayer graphene.
NewsArticle: "How superconductivity arises: New insights from moiré materials" https://phys.org/news/2026-02-superconductivity-insights-moi...
westurner•1h ago
westurner•1h ago
From "Did the Particle Go Through the Two Slits, or Did the Wave Function?" https://news.ycombinator.com/item?id=43388542 :
> "Quantum microscopy study makes electrons visible in slow motion" https://news.ycombinator.com/item?id=40981054 :
"Terahertz spectroscopy of collective charge density wave dynamics at the atomic scale" (2024) https://www.nature.com/articles/s41567-024-02552-7 :
>> Here, by utilizing terahertz pump–probe spectroscopy in a scanning tunnelling microscope,
> "Topological gauge theory of vortices in type-III superconductors" https://news.ycombinator.com/item?id=41803662 :
"Topological gauge theory of vortices in type-III superconductors" (2024) https://link.aps.org/doi/10.1103/PhysRevB.110.094506
From https://news.ycombinator.com/item?id=40360691 :
"Observation of current whirlpools in graphene at room temperature" (2024) https://www.science.org/doi/10.1126/science.adj2167 :
> Using a nanoscale scanning magnetometer, we imaged a distinctive hydrodynamic transport pattern—stationary current vortices—in a monolayer graphene device at room temperature. By measuring devices with increasing characteristic size, we observed the disappearance of the current vortex and thus verified a prediction of the hydrodynamic model. We further observed that vortex flow is present for both hole- and electron-dominated transport regimes but disappears in the ambipolar regime. We attribute this effect to a reduction of the vorticity diffusion length near charge neutrality. Our work showcases the power of local imaging techniques for unveiling exotic mesoscopic transport phenomena.