A general theory of thermal magnetic fluctuations near the surface of conductive and/or magnetically permeable slabs is developed; such fluctuations are the magnetic analog of Johnson voltage noise. Starting with the fluctuation-dissipation theorem and Maxwell’s equations, a closed-form expression for the magnetic noise spectral density is derived. Quantum decoherence, as induced by thermal mag...

We investigate the interplay of magnetic fluctuations and Cooper pairing in twisted bilayer graphene from a purely microscopic model within large-scale tight-binding approach resolving \AA ngstr\"om scale. For local onsite repulsive interactions using random-phase approximation for spin fluctuations, we derive effective interaction that use self-consistent solutions Bogoliubov-de-Gennes equatio...