Topological Cooper Scaffold: Proximity-Induced Nodal-Line Protection as a Pathway Toward Elevated-Tc Superconductivity in Magic-Angle Twisted Bilayer Graphene

We propose a conceptual framework and practical experimental protocol for elevating the superconducting critical temperature (Tc) of magic-angle twisted bilayer graphene (MATBG) through proximity-induced topological protection. The central hypothesis — termed the Topological Cooper Scaffold — draws on three recent experimental developments: (i) the discovery of room-temperature-stable magnetic nodal lines in elemental cobalt (Sánchez-Barriga et al., HZB Berlin, 2026), (ii) the demonstration of gate-tunable cobalt-proximity effects in graphene heterostructures (Nature Communications, 2026), and (iii) the confirmation of strong electron–phonon coupling in superconducting MATBG (Nature, 2024). We argue that an ultrathin cobalt layer, electrically decoupled from MATBG by a hexagonal boron nitride (hBN) spacer of 1–2 monolayers, can transfer nodal-line spin texture into the flat-band electronic structure of MATBG via interfacial exchange coupling. This suppresses the dominant intervalley phonon-scattering decoherence channel without introducing sufficient pair-breaking to destroy the superconducting condensate. The proposed heterostructure — graphite gate / hBN / MATBG / hBN spacer / ultrathin Co / hBN cap — is fabricable with existing van der Waals assembly techniques and requires no new instrumentation beyond standard dilution refrigerator transport setups. We predict a measurable upward shift in Tc of 0.5–2 K above the bare MATBG baseline of ~1.7 K, with gate-voltage tunability of that shift and enhancement of the upper critical field Hc2 beyond the Pauli limit. Five falsifiable transport predictions are outlined, including spacer-thickness-dependent null controls that isolate the proximity mechanism from strain and electrostatic artifacts. The broader conceptual contribution is the identification of symmetry-based decoherence suppression as a distinct design axis for superconductor engineering — inspired by the isolation principle that enables the thorium-229 nuclear clock (demonstrated 2026) to achieve unprecedented frequency precision by decoupling an oscillator from environmental perturbation. Whether the same principle, applied at the electronic rather than nuclear scale, can contribute to the pursuit of ambient-pressure room-temperature superconductivity is framed as an open and experimentally accessible question. The paper includes full theoretical framework, BCS-based quantitative estimates, heterostructure design specifications, measurement protocol, and bibliography of 13 primary sources.