Pseudospin Paramagnons and the Superconducting Dome in Magic Angle Twisted Bilayer Graphene

Abstract

We present a theory of superconductivity in twisted bilayer graphene in which attraction is generated between electrons on the same honeycomb sublattice when the system is close to a sublattice polarization instability. The resulting Cooper pairs are spin-polarized valley-singlets. Because the sublattice polarizability is mainly contributed by interband fluctuations, superconductivity occurs over a wide range of filling fraction. It is suppressed by i) applying a sublattice polarizing field (generated by an aligned BN substrate) or ii) changing moiré band filling to favor valley polarization. The enhanced intrasublattice attraction close to sublattice polarization instability is analogous to enhanced like-spin attraction in liquid ${}^3$He near the melting curve and the enhanced valley-singlet repulsion close to valley-polarization instabilities is analogous to enhanced spin-singlet repulsion in metals that are close to a ferromagnetic instability. We comment on the relationship between our pseudospin paramagnon model and the rich phenomenology of superconductivity in twisted bilayer and multilayer graphene.

maintext 5 pages, 3 figures

References in corpus (5)

• Tunable Phase Boundaries and Ultra-Strong Coupling Superconductivity in Mirror Symmetric Magic-Angle Trilayer Graphene
• Superconductivity in rhombohedral trilayer graphene
• Isospin magnetism and spin-triplet superconductivity in Bernal bilayer graphene
• Quantized Transport in Graphene p-n Junctions in Magnetic Field
• Coulomb interaction, phonons, and superconductivity in twisted bilayer graphene

Cited by in corpus (12)

• Superconductivity in Twisted Double Bilayer Graphene Stabilized by WSe${}_2$
• Spin and Orbital Metallic Magnetism in Rhombohedral Trilayer Graphene
• Dirac cone spectroscopy of strongly correlated phases in twisted trilayer graphene
• Nodal band-off-diagonal superconductivity in twisted graphene superlattices
• Electron spin resonance and collective excitations in magic-angle twisted bilayer graphene
• Pair Density Waves from Local Band Geometry
• Euler Obstructed Cooper Pairing in Twisted Bilayer Graphene: Nematic Nodal Superconductivity and Bounded Superfluid Weight
• Superconductivity from spin fluctuations and long-range interactions in magic-angle twisted bilayer graphene
• Competition of Exchange and Correlation Energies in Two-Dimensional $N$-component Electron Gas Ferromagnetism
• Spectroscopic signature of spin triplet odd-valley superconductivity in two-dimensional materials
• Mean-field Modelling of Moiré Materials: A User's Guide with Selected Applications to Twisted Bilayer Graphene
• Decomposing Electronic Structures in Twisted Multilayers: Bridging Spectra and Incommensurate Wave Functions