Charge order and broken rotational symmetry in magic-angle twisted bilayer graphene

By Yuhang Jiang, Xinyuan Lai, Kenji Watanabe, Takashi Taniguchi, K. Haule, J. Mao, E. Andrei. Nature, 2019

697 citations recorded by the source corpus.

Bilayer graphene can be modified by rotating (twisting) one layer with respect to the other. The interlayer twist gives rise to a moiré superlattice that affects the electronic motion and alters the band structure1–4. Near a ‘magic angle’ of twist2,4, where the emergence of a flat band causes the charge carriers to slow down3, correlated electronic phases including Mott-like insulators and superconductors were recently discovered5–8 by using electronic transport. These measurements revealed an intriguing similarity between magic-angle twisted bilayer graphene and high-temperature superconductors, which spurred intensive research into the underlying physical mechanism9–14. Essential clues to this puzzle, such as the symmetry and spatial distribution of the spectral function, can be accessed through scanning tunnelling spectroscopy. Here we use scanning tunnelling microscopy and spectroscopy to visualize the local density of states and charge distribution in magic-angle twisted bilayer graphene. Doping the sample to partially fill the flat band, we observe a pseudogap phase accompanied by a global stripe charge order that breaks the rotational symmetry of the moiré superlattice. Both the pseudogap and the stripe charge order disappear when the band is either empty or full. The close resemblance to similar observations in high-temperature superconductors15–21 provides new evidence of a deeper link underlying the phenomenology of these systems. When scanning tunnelling spectroscopy is used to map the electronic structure of magic-angle twisted bilayer graphene, a pseudogap phase is found, accompanied by a global charge-ordered stripe phase.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/49589b9066ab6eceaa9f00f73aee067bdde148ec

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In Atomic and Molecular Physics, and Optics

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Citations in the corpus

Symmetry-broken Chern insulators and Rashba-like Landau-level crossings in magic-angle bilayer graphene (2020, background): “1° (MATBG), ultra-flat moiré bands (1-6) host strongly interacting electrons which give rise to a plethora of phases including correlated insulators (CI)(1, 7-10), superconductors (SC)(2, 7, 11-21) and orbital magnets (OM)(7, 22-24).”
Superconductivity, superfluidity and quantum geometry in twisted multilayer systems (2021, background): “The normal state above the critical temperature is also likely to reveal interesting preformed pair, pseudogap or insulator behavior characteristic for a flat band [47, 48, 60, 109, 152].”