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arXiv · 2208.12039

Unconventional superconductivity with preformed pairs in twisted bilayer graphene

SK Firoz Islam·A. Yu. Zyuzin·Alexander A. Zyuzin
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Abstract

We present a theory of superconductivity in magic-angle twisted bilayer graphene and analyze the superconducting phase diagram in presence of the magnetic field. Namely, we consider a model of a granular array hosting localized states, which are hybridized via the delocalized fermions in the inter-grain regions. We study a strong coupling situation when the interactions lead to an incoherent state with preformed Cooper pairs inside the grains. The Andreev scattering among different grains manifests itself through the global phase-coherent superconducting state at lower temperatures. We demonstrate that a new phase transition between the preformed Cooper pairing state and the Larkin-Ovchinnikov-Fulde-Ferrell state might be induced by the spin pair-breaking effect of in-plane magnetic field. The upper critical magnetic field is shown to be enhanced in the strong coupling case.

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SK Firoz Islam, A. Yu. Zyuzin, Alexander A. Zyuzin. 2022-08-25. Unconventional superconductivity with preformed pairs in twisted bilayer graphene. https://doi.org/10.1103/physrevb.107.l060503

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