Nematicity and competing orders in superconducting magic-angle graphene

Cao, Yuan; Rodan-Legrain, Daniel; Park, Jeong Min; Yuan, Noah F. Q.; Watanabe, Kenji; Taniguchi, Takashi; Fernandes, Rafael M.; Fu, Liang; Jarillo‐Herrero, Pablo

doi:10.1126/science.abc2836

Cited by 328 publications

(180 citation statements)

References 62 publications

Supporting

Mentioning

167

Contrasting

Unclassified

Order By: Relevance

“…Since the discovery of superconductivity in proximity to correlated insulator states at half (electron or hole) filling of the flat bands [1,2], there has been great interest in the electronic properties of magic-angle twisted bilayer graphene (tBLG) [3]. Additional experiments [4][5][6][7][8][9][10] discovered correlated insulator phases and superconductivity at other doping levels of the flat bands and revealed a wide range of interesting phenomena [11,12] including strange metal behavior [13,14], ferromagnetic order [15,16], superconductivity without correlated insulators [17][18][19], Chern insulators [20][21][22], and nematic order [6,[23][24][25].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

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

et al. 2021

View full text Add to dashboard Cite

show abstract

“…Graphene‐based moiré heterostructures, such as MATBG, exhibit strong electron−electron interactions, which result in flat energy bands near the zero Fermi energy and cause a series of correlated phenomena. [ 162 , 163 , 164 ] Correlation refers to the instantaneous interaction between electrons, that is, two or more valence electrons appearing around an atom cause a strong interaction. When electrons form a pair through an attractive interaction, the electron pair can coherently be condensed to form a superconductor.…”

Section: Correlated Physical Performances In Graphene‐based Moiré Heterostructuresmentioning

confidence: 99%

Developing Graphene‐Based Moiré Heterostructures for Twistronics

Liu

Wang

2021

Advanced Science

View full text Add to dashboard Cite

Graphene-based moiré heterostructures are strongly correlated materials, and they are considered to be an effective platform to investigate the challenges of condensed matter physics. This is due to the distinct electronic properties that are unique to moiré superlattices and peculiar band structures. The increasing research on strongly correlated physics via graphene-based moiré heterostructures, especially unconventional superconductors, greatly promotes the development of condensed matter physics. Herein, the preparation methods of graphene-based moiré heterostructures on both in situ growth and assembling monolayer 2D materials are discussed. Methods to improve the quality of graphene and optimize the transfer process are presented to mitigate the limitations of low-quality graphene and damage caused by the transfer process during the fabrication of graphene-based moiré heterostructures. Then, the topological properties in various graphene-based moiré heterostructures are reviewed. Furthermore, recent advances regarding the factors that influence physical performances via a changing twist angle, the exertion of strain, and regulation of the dielectric environment are presented. Moreover, various unique physical properties in graphene-based moiré heterostructures are demonstrated. Finally, the challenges faced during the preparation and characterization of graphene-based moiré heterostructures are discussed. An outlook for the further development of moiré heterostructures is also presented.

show abstract

“…from detailed ab initio studies or spectroscopic probes of the band structure over a range of twist angles, it is difficult to make quantitative contact with experiments such as Ref. 41 which show a dome in T c near the magic angle. Any comparison would also inevitably be complicated by the presence of confounding variables such as twist angle disorder 99 which are difficult to fully characterize, let alone control.…”

Section: Skyrmion Superconductivitymentioning

confidence: 99%

“…1), whose stabilization arises from the particular features of the strong-coupling Hamiltonian. Such unconventional Cooper pairs may be relevant for understanding the various superconducting domes in TBG [2][3][4][41][42][43][44][45] , whose properties and origins remain the subject of intense debate.…”

Section: Introductionmentioning

confidence: 99%

Skyrmions in twisted bilayer graphene: stability, pairing, and crystallization

Kwan¹,

Wagner²,

Bultinck³

et al. 2021

Preprint

View full text Add to dashboard Cite

We study the excitations that emerge upon doping the translationally-invariant correlated insulating states in magic angle twisted bilayer graphene at various integer filling factors ν. We identify parameter regimes where these are associated with skyrmion textures in the spin or pseudospin degrees of freedom, and explore both short-distance pairing effects and the formation of long-range ordered skyrmion crystals. We perform a comprehensive analysis of the pseudospin skyrmions that emerge upon doping insulators at even ν, delineating the regime in parameter space where these are the lowest-energy charged excitations by means of self-consistent Hartree-Fock calculations on the interacting Bistritzer-MacDonald model. We explicitly demonstrate the purely electron-mediated pairing of skyrmions, a key ingredient behind a recent proposal of skyrmion superconductivity. Building upon this, we construct hopping models to extract the effective masses of paired skyrmions, and discuss our findings and their implications for skyrmion superconductivity in relation to experiments, focusing on the dome-shaped dependence of the transition temperature on the twist angle. We also investigate the properties of spin skyrmions about the quantized anomalous Hall insulator at ν = +3. In both cases, we demonstrate the formation of robust spin/pseudospin skyrmion crystals upon doping to a finite density away from integer filling.

show abstract

Nematicity and competing orders in superconducting magic-angle graphene

Cited by 328 publications

References 62 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

Developing Graphene‐Based Moiré Heterostructures for Twistronics

Skyrmions in twisted bilayer graphene: stability, pairing, and crystallization

Contact Info

Product

Resources

About