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We use self-consistent Hartree-Fock calculations performed in the full $\pi$-band Hilbert space to assess the nature of the recently discovered correlated insulator states in magic-angle twisted bilayer graphene (TBG). We find that gaps…

Strongly Correlated Electrons · Physics 2020-03-11 Ming Xie , Allan H. MacDonald

Twisted bilayer graphene with a twist angle of around 1.1{\deg} features a pair of isolated flat electronic bands and forms a strongly correlated electronic platform. Here, we use scanning tunneling microscopy to probe local properties of…

We theoretically study the band structure and optical conductivity of twisted bilayer graphene (TBG) near the magic angle considering the effects of lattice relaxation. We show that the optical conductivity spectrum is characterized by a…

Mesoscale and Nanoscale Physics · Physics 2021-02-03 Lu Wen , Zhiqiang Li , Yan He

In the magic-angle twisted bilayer graphene (MA-TBG), strong electron-electron (e-e) correlations caused by the band-flattening lead to many exotic quantum phases such as superconductivity, correlated insulator, ferromagnetism, and quantum…

Materials Science · Physics 2020-05-29 Ya-Ning Ren , Chen Lu , Yu Zhang , Si-Yu Li , Yi-Wen Liu , Chao Yan , Zi-Han Guo , Cheng-Cheng Liu , Fan Yang , Lin He

Twisted bilayer graphene (TBG) represents a highly tunable, strongly correlated electron system owed to its unique flat electronic bands. However, understanding the single-particle band structure alone has been challenging due to complex…

We show that the entire continuous model of twisted bilayer graphene (TBG) (and not just the two active bands) with particle-hole symmetry is anomalous and hence incompatible with a lattice model. Previous works, e.g., [Phys. Rev. Lett.…

Mesoscale and Nanoscale Physics · Physics 2022-04-29 Zhi-Da Song , Biao Lian , Nicolas Regnault , B. Andrei Bernevig

Two monolayers of graphene twisted by a small `magic' angle exhibit nearly flat bands leading to correlated electronic states and superconductivity, whose precise nature including possible broken symmetries, remain under debate. Here we…

Strongly Correlated Electrons · Physics 2019-12-13 Jong Yeon Lee , Eslam Khalaf , Shang Liu , Xiaomeng Liu , Zeyu Hao , Philip Kim , Ashvin Vishwanath

The recent constructions of flat moir\'e minibands in specifically twisted multilayer graphene and twisted transition metal dichalcogenides (TMDs) have facilitated the observation of strong correlations with a convenient tunability. These…

Mesoscale and Nanoscale Physics · Physics 2024-04-05 Jihang Zhu , Dawei Zhai , Cong Xiao , Wang Yao

We propose a method for studying the strong interaction regimes in twisted bilayer graphene using hybrid Wannier functions, that are Wannier-like in one direction and Bloch-like in the other. We focus on the active bands as given by the…

Mesoscale and Nanoscale Physics · Physics 2021-03-24 Kasra Hejazi , Xiao Chen , Leon Balents

This study theoretically investigates the contact conductance in twisted bilayer graphene (TBG), providing a theoretical explanation for recent experimental observations from scanning tunneling microscopy (STM) and conductive atomic force…

Mesoscale and Nanoscale Physics · Physics 2025-06-30 Kevin J. U. Vidarte , Caio Lewenkopf , F. Crasto de Lima , R. Hiroki Miwa , Felipe Pérez Riffo , Eric Suárez Morell

Anomalous gating effects-such as gate ineffectiveness and pronounced hysteresis-have been observed in graphene-based systems encapsulated in boron nitride (BN) and linked to a possible ferroelectric state. However, their origin, stability,…

Mesoscale and Nanoscale Physics · Physics 2025-06-09 G. Maffione , L. S. Farrar , M. Kapfer , K. Watanabe , T. Taniguchi , H. Aubin , D. Mailly , R. Ribeiro-Palau

Twisted bilayer graphene (tBLG) provides us with a large rotational freedom to explore new physics and novel device applications, but many of its basic properties remain unresolved. Here we report the synthesis and systematic Raman study of…

Twisted bilayer graphene (TBG) is known to have disorder in its twist angle. We show that in terms of a Dirac equation with a random gauge potential ${\bf A}({\bf r})$ this disorder becomes huge when the average twist angle is near the…

Mesoscale and Nanoscale Physics · Physics 2025-08-12 Baruch Horovitz , Pierre Le Doussal

We investigate twisted double bilayer graphene (TDBG), a four-layer system composed of two AB-stacked graphene bilayers rotated with respect to each other by a small angle. Our ab initio band structure calculations reveal a considerable…

Mesoscale and Nanoscale Physics · Physics 2020-04-22 Fatemeh Haddadi , QuanSheng Wu , Alex J. Kruchkov , Oleg V. Yazyev

Twisted bilayer graphene near the magic angle is known to have a cascade of insulating phases at integer filling factors of the low-energy bands. In this Letter we address the nature of these phases through an unrestricted, large-scale…

Strongly Correlated Electrons · Physics 2024-09-30 Khagendra Adhikari , Kangjun Seo , K. S. D. Beach , Bruno Uchoa

The moir\'e superlattice formed by ABC stacked trilayer graphene aligned with a hexagonal boron nitride substrate (TG/h-BN) provides an interesting system where both the bandwidth and the topology can be tuned by an applied perpendicular…

Strongly Correlated Electrons · Physics 2019-06-05 Ya-Hui Zhang , T. Senthil

We discuss the effect of long-range interactions within the self-consistent Hartree-Fock (HF) approximation in comparison to short-range atomic Hubbard interactions on the band structure of twisted bilayer graphene (TBG) at charge…

Strong correlations occur in magic-angle twisted bilayer graphene (MATBG) when the octet of flat moir\'e minibands centered on charge neutrality (CN) is partially occupied. The octet consists of a single valence band and a single conduction…

Strongly Correlated Electrons · Physics 2024-10-18 Jihang Zhu , Iacopo Torre , Marco Polini , Allan H. MacDonald

We study the electron-phonon coupling in twisted bilayer graphene (TBG), which was recently experimentally observed to exhibit superconductivity around the magic twist angle $\theta\approx 1.05^\circ$. We show that phonon-mediated electron…

Mesoscale and Nanoscale Physics · Physics 2019-07-03 Biao Lian , Zhijun Wang , B. Andrei Bernevig

We show that the recently observed superconductivity in twisted bilayer graphene (TBG) can be explained as a consequence of the Kohn-Luttinger (KL) instability which leads to an effective attraction between electrons with originally…

Mesoscale and Nanoscale Physics · Physics 2019-01-21 J. González , T. Stauber