Pairing symmetry of twisted bilayer graphene: a phenomenological synthesis

Abstract

One of the outstanding questions in the study of twisted bilayer graphene -- from both experimental and theoretical points of view -- is the nature of its superconducting phase. In this work we perform a comprehensive synthesis of existing experiments, and argue that experimental constraints are strong enough to allow the structure of the superconducting order parameter to be nearly uniquely determined. In particular, we argue that the order parameter is nodal, and is formed from an admixture of spin-singlet and spin-triplet Cooper pairs. This argument is made on phenomenological grounds, without committing to any particular microscopic model of the superconductor. Existing data is insufficient to determine the orbital parity of the order parameter, which could be either p-wave or d-wave. We propose a way in which the measurement of Andreev edge states can be used to distinguish between the two.

10+12 pages; 3+5 figures; v3: highlighted result of STM conductance calculation

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Cited by in corpus (38)

• Spin-Orbit Enhanced Superconductivity in Bernal Bilayer Graphene
• Superconductivity and strong interactions in a tunable moiré quasiperiodic crystal
• Quantum textures of the many-body wavefunctions in magic-angle graphene
• Superconductivity and correlated phases in non-twisted bilayer and trilayer graphene
• Superconductivity in Twisted Double Bilayer Graphene Stabilized by WSe${}_2$
• Superconductivity from electronic interactions and spin-orbit enhancement in bilayer and trilayer graphene
• Stabilizing fluctuating spin-triplet superconductivity in graphene via induced spin-orbit coupling
• Nodal band-off-diagonal superconductivity in twisted graphene superlattices
• Electron spin resonance and collective excitations in magic-angle twisted bilayer graphene
• Electron-phonon coupling and competing Kekulé orders in twisted bilayer graphene
• Andreev Reflection in Scanning Tunneling Spectroscopy of Unconventional Superconductors
• Junctions and superconducting symmetry in twisted bilayer graphene
• Andreev reflection spectroscopy in strongly paired superconductors
• Vestigial singlet pairing in a fluctuating magnetic triplet superconductor: Applications to graphene moiré systems
• Topological flat bands, valley polarization, and interband superconductivity in magic-angle twisted bilayer graphene with proximitized spin-orbit couplings
• Nonlocal Moments in the Chern Bands of Twisted Bilayer Graphene
• Approximate symmetries, insulators, and superconductivity in continuum-model description of twisted WSe${}_2$
• Nematic versus Kekulé phases in twisted bilayer graphene under hydrostatic pressure
• Tunable superconductivity and Möbius Fermi surfaces in an inversion-symmetric twisted van der Waals heterostructure
• Probing the order parameter symmetry of two-dimensional superconductors by twisted Josephson interferometry
• Role of the Berry curvature on BCS-type superconductivity in two-dimensional materials
• Intrinsic non-magnetic ${\varphi }_0$ Josephson junctions in twisted bilayer graphene
• Disorder-dependent superconducting pairing symmetry in doped graphene
• Eliashberg Theory and Superfluid Stiffness of Band-Off-Diagonal Pairing in Twisted Graphene
• Superconductivity in a Topological Lattice Model with Strong Repulsion
• Insulators at Fractional Fillings in Twisted Bilayer Graphene Partially Aligned to Hexagonal Boron Nitride
• Topological Kondo effect with spinful Majorana fermions
• Local condensation of charge-$4e$ superconductivity at a nematic domain wall
• Nematic superconductivity from selective orbital pairing in Ba(Fe1-xMx)2As2 (M = Co, Ni) single crystals
• Supercurrent-induced Anomalous Thermal Hall Effect as a New Probe to Superconducting Gap Anisotropy
• Tunneling spectra of impurity states in unconventional superconductors
• Probing superconductivity with tunneling spectroscopy in rhombohedral graphene
• Topological two-band electron-hole superconductors with $d$-wave symmetry: Absence of Dirac quasiparticle annihilation in magic-angle twisted trilayer graphene
• The role of electromagnetic gauge-field fluctuations in the selection between chiral and nematic superconductivity
• Momentum-resolved spectroscopy of superconductivity with the quantum twisting microscope
• Displacement-field-tunable superconductivity in an inversion-symmetric twisted van der Waals heterostructure
• Optical and Raman selection rules for odd-parity clean superconductors
• Mean-field Modelling of Moiré Materials: A User's Guide with Selected Applications to Twisted Bilayer Graphene