Isospin and momentum polarized orders in bilayer graphene

Dong, Zhenghong; Davydova, Margarita; Ogunnaike, Olumakinde; Levitov, Leonid

doi:10.48550/arxiv.2110.15254

Cited by 2 publications

(2 citation statements)

References 36 publications

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“…On top of this cascade of isospin orders, other symmetry-breaking orders are predicted theoretically, e.g. the momentum space polarization wherein all carriers are shifted into one, two or three pockets at the band minima produced by the trigonal warping effects [51,52].…”

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confidence: 98%

Spin-triplet superconductivity at the onset of isospin order in biased bilayer graphene

Dong¹,

Chubukov²,

Levitov³

2022

Preprint

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The quest for unconventional superconductivity governed by Coulomb repulsion between electrons rather than phonon attraction received new momentum with the advent of moiré graphene. Initially, delineating the phonon and Coulomb-repulsion-based pairing mechanisms has proven to be a challenging task, however the situation has changed after recent discovery of superconductivity in non-twisted graphene bilayers and trilayers. Superconductivity occurring at the phase boundaries of spin and valley polarized orders calls for non-phonon scenarios, yet the specific pairing mechanisms remain to be understood. Here we analyze a striking example -superconductivity in graphene bilayers occurring at the onset of valley-polarized order induced by a magnetic field. We describe an attraction-from-repulsion mechanism for pairing mediated by a quantum-critical mode, which fully explains the observed phenomenology. While it is usually notoriously difficult to infer the pairing mechanism from the observed superconducting phases, this case presents a rare exception, allowing for a fairly unambiguous identification of the origin of the pairing glue. A combination of factors such as the location of superconducting phase at the onset of isospin-polarized phase, a threshold in a magnetic field, above which superconductivity occurs, and its resilience at high magnetic fields paints a clear picture of a triplet superconductivity driven by quantum-critical fluctuations.

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mentioning

confidence: 98%

Spin-triplet superconductivity at the onset of isospin order in biased bilayer graphene

Dong¹,

Chubukov²,

Levitov³

2022

Preprint

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“…Note added: Recently, we found that Ref. [29] discusses momentum condensation ("flocking" effect) in Bernal bilayer graphene with three disjoint Fermi pockets whose microscopic origin is similar to the formation of nematic Fermi surface we discuss here in ABC trilayer graphene.…”

Section: At Low Carrier Densities |𝑛 𝑒 |mentioning

confidence: 91%

Spin and Orbital Metallic Magnetism in Rhombohedral Trilayer Graphene

Huang¹,

Wolf²,

Wei³

et al. 2022

Preprint

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We provide a complete theoretical interpretation of the metallic broken spin/valley symmetry states recently discovered in ABC trilayer graphene (ABC) perturbed by a large transverse displacement field. Our conclusions combine insights from ABC trilayer graphene electronic structure models and mean field theory, and are guided by precise magneto-oscillation Fermi-surface-area measurements. We conclude that the physics of ABC trilayer graphene is shaped by the principle of momentum-space condensation, which favors Fermi surface reconstructions enabled by broken spin/valley flavor symmetries when the single-particle bands imply thin annular Fermi seas. We find one large outer Fermi surface enclosed majority-flavor states and one or more small inner hole-like Fermi surfaces enclosed minority-flavor states that are primarily responsible for nematic order. The smaller surfaces can rotate along a ring of van-Hove singularities or reconstruct into multiple Fermi surfaces with little cost in energy. We propose that the latter property is responsible for the quantum oscillation frequency fractionalization seen experimentally in some regions of the carrier-density/displacement-field phase diagram.

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Isospin and momentum polarized orders in bilayer graphene

Cited by 2 publications

References 36 publications

Spin-triplet superconductivity at the onset of isospin order in biased bilayer graphene

Spin-triplet superconductivity at the onset of isospin order in biased bilayer graphene

Spin and Orbital Metallic Magnetism in Rhombohedral Trilayer Graphene

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