Moiré lattice effects on the orbital magnetic response of twisted bilayer graphene and Condon instability

Guerci, Daniele; Simon, Pascal; Mora, Christophe

doi:10.1103/physrevb.103.224436

Cited by 12 publications

(9 citation statements)

References 86 publications

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“…Our observation also links with a recent publication stating that the divergent paramagnetic response in twisted bilayer graphene can lead to a permanent in-plane magnetic moment [45]. Note that this is not possible in one layer with a perpendicular magnetic moment [42].…”

Section: Magnetic Instability In Neutral Aa-stacked Bilayer Graphenesupporting

confidence: 89%

Collective magnetic excitations in AA- and AB-stacked graphene bilayers

2021

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We discuss novel transverse plasmon polaritons that are hosted by AA-and AB-stacked bilayer graphene due to perfect nesting. They are composed of oscillating counterflow currents in between the layers, giving a clear interpretation of these collective modes as magnetic excitations carrying magnetic moments parallel to the planes. For AA-stacked bilayer graphene, these modes can reach zero frequency at the neutrality point and we thus predict a symmetry-broken ground state leading to in-plane orbital ferromagnetism. Even though it could be hard to detect them in real solid-state devices, these novel magnetic plasmons should be observable in artificial setups such as optical lattices. Also, our results might be relevant for magic angle twisted bilayer graphene samples, as their electronic properties are mostly determined by confined AA-stacked regions.

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Section: Magnetic Instability In Neutral Aa-stacked Bilayer Graphenesupporting

confidence: 89%

Collective magnetic excitations in AA- and AB-stacked graphene bilayers

2021

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“…As in twisted bilayer graphene, the electronic wave functions at the magic angle are highly localized around the AA-stacked islands, [6] there might be the possibility of a Condon instability in twisted bilayer graphene around θ m . [40] The imaginary part of the conductivity or magnetic Drude weight is obtained from the Kramers-Kronig relation which can be split into the following two contributions…”

Section: Condon Instability At the Magic Anglementioning

confidence: 99%

“…This value, obtained for

κ = 1

, is slightly larger than the one reported in ref. [40] for the continuum model with

κ = 0.2

.…”

Section: Optical Response Around the Magic Anglementioning

confidence: 99%

“…Apart from the above, the large counterflow or magnetic response has also been discussed in several articles. [ 7,17,40 ] Nevertheless, the importance of acoustic plasmonic modes has not received sufficient attention, so far. We believe that our results will be relevant to flat‐band plasmonics in twisted bilayer graphene, especially at the chiral resonance where the energy density can be largely enhanced.…”

Section: Introductionmentioning

confidence: 99%

“…[36][37][38][39] We will argue that the Condon instability arises in the continuum model [1,7] of twisted bilayer graphene at the neutrality point in the immediate vicinity of the magic angle.Apart from the above, the large counterflow or magnetic response has also been discussed in several articles. [7,17,40] Nevertheless, the importance of acoustic plasmonic modes has not received sufficient attention, so far. We believe that our results will be relevant to flat-band plasmonics in twisted bilayer graphene, especially at the chiral resonance where the energy density can be largely enhanced.Finally, the chirality in graphene might be used to design novel cavities that lead to strong chiral light-matter interaction.…”

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confidence: 99%

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Neutral Magic‐Angle Bilayer Graphene: Condon Instability and Chiral Resonances

et al. 2023

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The full optical response of twisted bilayer graphene at the neutrality point close to the magic angle within the continuum model (CM) is discussed. First, three different channels consistent with the underlying D 3 symmetry are identified, yielding the total, magnetic, and chiral response. Second, the full optical response in the immediate vicinity of the magic angle θ normalm is numerically calculated, which provides a direct mapping of the CM onto an effective two‐band model. It is, further, shown that the ground state of the CM in the immediate vicinity of θ normalm is unstable toward transverse current fluctuations, a so‐called Condon instability. Third, due to the large counterflow, the acoustic plasmonic excitations with typical wave numbers have larger energies than the optical ones and their energy density may be largely enhanced at certain frequencies which are denominated as chiral resonances. Finally, symmetry relations for the optical response and their consequences for the chiral response are discussed.

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