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We report strong electron-phonon coupling in magic-angle twisted bilayer graphene (MA-TBG) obtained from atomistic description of the system including more than 10000 atoms in the moire supercell. Electronic structure, phonon spectrum, and…

Mesoscale and Nanoscale Physics · Physics 2018-12-27 Young Woo Choi , Hyoung Joon Choi

We devise a model to explain why twisted bi-layer graphene (TBLG) exhibits insulating behavior when $\nu=2,3$ charges occupy a unit moir\'e cell, a feature attributed to Mottness, but not for $\nu=1$, clearly inconsistent with Mott…

Strongly Correlated Electrons · Physics 2018-10-15 Bikash Padhi , Chandan Setty , Philip W. Phillips

We carry out large-scale quantum Monte Carlo simulations of a candidate field theory for the onset of superconductivity in magic-angle twisted bilayer graphene. The correlated insulating state at charge neutrality spontaneously breaks U(1)…

Strongly Correlated Electrons · Physics 2023-05-04 Disha Hou , Yuhai Liu , Toshihiro Sato , Fakher F. Assaad , Wenan Guo , Zhenjiu Wang

The search for robust topological superconductivity and Majorana bound states continues, exploring both one-dimensional (1D) systems such as semiconducting nanowires and two-dimensional (2D) platforms. In this work we study a 2D approach…

Mesoscale and Nanoscale Physics · Physics 2023-04-21 Fernando Peñaranda , Ramón Aguado , Elsa Prada , Pablo San-Jose

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

Determining the symmetry breaking order of correlated quantum phases is essential for understanding the microscopic interactions in their host systems. The flat bands in magic angle twisted bilayer graphene (MATBG) provide an especially…

Mesoscale and Nanoscale Physics · Physics 2024-10-23 Jesse C. Hoke , Yifan Li , Julian May-Mann , Kenji Watanabe , Takashi Taniguchi , Barry Bradlyn , Taylor L. Hughes , Benjamin E. Feldman

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

We apply cluster dynamical mean field theory with an exact-diagonalization impurity solver to a Hubbard model for magic-angle twisted bilayer graphene, built on the tight-binding model proposed by Kang and Vafek (2018), which applies to the…

Strongly Correlated Electrons · Physics 2021-07-21 B. Pahlevanzadeh , P. Sahebsara , D. Sénéchal

We investigate the band structure of twisted monolayer-bilayer graphene (tMBG), or twisted graphene on bilayer graphene (tGBG), as a function of twist angles and perpendicular electric fields in search of optimum conditions for achieving…

Mesoscale and Nanoscale Physics · Physics 2020-07-15 Youngju Park , Bheema Lingam Chittari , Jeil Jung

Twisted bilayer systems with discrete magic angles, such as twisted bilayer graphene featuring moir\'{e} superlattices, provide a versatile platform for exploring novel physical properties. Here, we discover a class of superflat bands in…

Optics · Physics 2022-05-31 Hongfei Wang , Shaojie Ma , Shuang Zhang , Dangyuan Lei

The stacking and bending of graphene are trivial but extremely powerful agents of control over graphene's manifold physics. By changing the twist angle, one can drive the system over a plethora of exotic states via strong electron…

Mesoscale and Nanoscale Physics · Physics 2020-02-19 Jana Vejpravova , Barbara Pacakova , Mildred S. Dresselhaus , Jing Kong , Martin Kalbac

We study the single- and many-particle properties of a two-leg ladder model threaded by a flux with the legs coupled by a spatially varying term. Although a priori unrelated to twisted bilayer graphene (TBG), the model is found to have…

Strongly Correlated Electrons · Physics 2020-10-29 Yixuan Huang , Pavan Hosur , Hridis K. Pal

Moir\'e lattices provide a highly tunable platform for exploring the interplay between electronic correlations and band topology. Introducing a second moir\'e pattern extends this paradigm: interference between the two moir\'e patterns…

Recent experiments on magic-angle twisted bilayer graphene have discovered correlated insulating behavior and superconductivity at a fractional filling of an isolated narrow band. In this paper we show that magic-angle bilayer graphene…

Near a magic twist angle, the lowest energy conduction and valence bands of bilayer graphene moir\'e superlattices become extremely narrow. The band dispersion that remains is sensitive to the moir\'e's strain pattern, nonlocal tunneling…

Mesoscale and Nanoscale Physics · Physics 2021-11-04 Ming Xie , Allan H. MacDonald

Very recently, twisted graphene bilayer (TGB) around the first magic angle 1.1{\deg} has attracted much attention for the realization of exotic quantum states, such as correlated insulator behavior and unconventional superconductivity. Here…

Materials Science · Physics 2019-04-10 Jia-Bin Qiao , Long-Jing Yin , Lin He

In Bernal-stacked bilayer graphene (BBG), the Landau levels give rise to an intimate connection between valley and layer degrees of freedom. Adding a moir\'e superlattice potential enriches the BBG physics with the formation of topological…

Mesoscale and Nanoscale Physics · Physics 2024-08-02 Yungi Jeong , Hangyeol Park , Taeho Kim , Kenji Watanabe , Takashi Taniguchi , Jeil Jung , Joonho Jang

Twisted bilayer graphene (TBG) exhibits a wide range of intriguing physical properties, such as superconductivity, ferromagnetism, and superlubricity. Depending on the twist angle, periodic moir\'e superlattices form in twisted bilayer…

Mesoscale and Nanoscale Physics · Physics 2022-06-07 Vahid Morovati , Zhiming Xue , Kenneth M. Liechti , Rui Huang

Twistronics is currently one of the most active research fields in condensed matter physics, following the discovery of correlated insulating and superconducting phases in twisted bilayer graphene (tBLG). Here, we present a magnonic…

Mesoscale and Nanoscale Physics · Physics 2020-09-17 Doried Ghader

Magic-angle twisted bilayer graphene (MATBG) exhibits a range of correlated phenomena that originate from strong electron-electron interactions. These interactions make the Fermi surface highly susceptible to reconstruction when $ \pm 1,…