Spin-fluctuation-induced pairing in twisted bilayer graphene

Fischer, Ammon; Klebl, Lennart; Honerkamp, Carsten; Kennes, Dante M.

doi:10.1103/physrevb.103.l041103

Cited by 38 publications

(22 citation statements)

References 60 publications

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“…Naively, one would expect that in this doping regime damped spin fluctuations from the magnetic parent state play an important role. However, Fischer and co-workers [79] recently demonstrated the possibility of pairing by AFM spin fluctuations in the vicinity of a FM phase. Future work will investigate the predictions of Hartree+U theory at noninteger doping levels to realize if long-ranged electron-electron interactions can also facilitate pairing by AFM spin fluctuations [80].…”

Section: Discussionmentioning

confidence: 99%

Importance of long-ranged electron-electron interactions for the magnetic phase diagram of twisted bilayer graphene

et al. 2021

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Electron-electron interactions are intrinsically long ranged, but many models of strongly interacting electrons only take short-ranged interactions into account. Here, we present results of atomistic calculations including both long-ranged and short-ranged electron-electron interactions for the magnetic phase diagram of twisted bilayer graphene and demonstrate that qualitatively different results are obtained when long-ranged interactions are neglected. In particular, we use Hartree theory augmented with Hubbard interactions and calculate the interacting spin susceptibility at a range of doping levels and twist angles near the first magic angle to identify the dominant magnetic instabilities. At the magic angle, mostly antiferromagnetic order is found, while ferromagnetism dominates at other twist angles. Moreover, long-ranged interactions significantly increase the twist angle window in which strong correlation phenomena can be expected. These findings are in good agreement with available experimental data.

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Section: Discussionmentioning

confidence: 99%

Importance of long-ranged electron-electron interactions for the magnetic phase diagram of twisted bilayer graphene

et al. 2021

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“…All of these systems have been predicted to feature flat electronic bands, which is a good indicator for possible strong correlations (tBLG [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68], tDBLG [69][70][71][72][73][74][75], AtAB [76][77][78][79], tTLG [78][79][80][81][82][83], ABC-hBN [41][42][43]). In both tBLG [84][85][86][87][88] and tTLG [83] long-ranged electronelectron interactions lead to an additional enhancement of the DOS which increases the robustness of electronic correlations, and could be one reason why robust superconductivity is observed in these materials [89,90].…”

Section: Introductionmentioning

confidence: 99%

Flat bands, electron interactions and magnetic order in magic-angle mono-trilayer graphene

Goodwin,

Klebl,

Vitale

et al. 2021

Preprint

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Starting with twisted bilayer graphene, graphene-based moiré materials have recently been established as a new platform for studying strong electron correlations. In this paper, we study twisted graphene monolayers on trilayer graphene and demonstrate that this system can host flat bands when the twist angle is close to the magic-angle of 1.16°. When monolayer graphene is twisted on ABA trilayer graphene (denoted AtABA), the flat bands are not isolated, but are intersected by a dispersive Dirac cone. In contrast, graphene twisted on ABC trilayer graphene (denoted AtABC) exhibits a gap between flat and remote bands. Since ABC trilayer graphene and twisted bilayer graphene are known to host broken symmetry phases, we further investigate magic-angle AtABC. We study the effect of electron-electron interactions in AtABC using both Hartree theory, and an atomic Hubbard theory to calculate the magnetic phase diagram as a function of doping, twist angle and perpendicular electric field. Our analysis reveals a rich variety of magnetic orderings, including ferromagnetism and ferrimagnetism, and demonstrates that a perpendicular electric field makes AtABC more susceptible to magnetic ordering.

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“…This conclusion is based on the observation that superconductivity emerges next to a strongly correlated state when the latter is suppressed by doping [9,10,21,28] and that the ratio of the critical temperature T c and Fermi temperature T F fits within the boundary of other unconventional superconductors [9,25,29]. These behaviors are similar to other high-T c superconductors where spin, orbital, and/or nematic fluctuations are believed to play a major role [28,[30][31][32][33][34]. On the other hand, recent experiments in magic-angle twisted bilayer graphene (MATBG) showed that the strongly correlated states and superconductivity are affected differently by the dielectric environment [18,19], which might point to a conventional origin, i.e., electron-phonon coupling, of the superconducting states.…”

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confidence: 92%

Doping fingerprints of spin and lattice fluctuations in moiré superlattice systems

Witt,

Pizarro,

Berges

et al. 2021

Preprint

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Spin-fluctuation-induced pairing in twisted bilayer graphene

Cited by 38 publications

References 60 publications

Importance of long-ranged electron-electron interactions for the magnetic phase diagram of twisted bilayer graphene

Importance of long-ranged electron-electron interactions for the magnetic phase diagram of twisted bilayer graphene

Flat bands, electron interactions and magnetic order in magic-angle mono-trilayer graphene

Doping fingerprints of spin and lattice fluctuations in moiré superlattice systems

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