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arXiv · 2203.09083

Functional Renormalization Group Study of Superconductivity in Rhombohedral Trilayer Graphene

Wei Qin·Chunli Huang·Tobias Wolf·Nemin Wei·Igor Blinov·Allan H. MacDonald
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Abstract

We employ a functional renormalization group approach to ascertain the pairing mechanism and symmetry of the superconducting phase observed in rhombohedral trilayer graphene. Superconductivity in this system occurs in a regime of carrier density and displacement field with a weakly distorted annular Fermi sea. We find that repulsive Coulomb interactions can induce electron pairing on the Fermi surface by taking advantage of momentum-space structure associated with the finite width of the Fermi sea annulus. The degeneracy between spin-singlet and spin-triplet pairing is lifted by valley-exchange interactions that strengthen under the RG flow and develop nontrivial momentum-space structure. We find that the leading pairing instability is $d$-wave-like and spin-singlet, and that the theoretical phase diagram versus carrier density and displacement field agrees qualitatively with experiment.

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Wei Qin, Chunli Huang, Tobias Wolf, Nemin Wei, Igor Blinov, Allan H. MacDonald. 2022-03-17. Functional Renormalization Group Study of Superconductivity in Rhombohedral Trilayer Graphene. https://doi.org/10.1103/physrevlett.130.146001

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