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Electron-phonon coupling directly determines the stability of cooperative order in solids, including superconductivity, charge and spin density waves. Therefore, the ability to enhance or reduce electron-phonon coupling by optical driving…

Using scanning probe microscopy and spectroscopy, we explore the spatial symmetry of the electronic wavefunctions of twisted bilayer graphene at the "magic angle" of 1.1 degrees. This small twist angle leads to a long wavelength moir\'e…

Mesoscale and Nanoscale Physics · Physics 2020-08-12 Zhiming Zhang , Rachel Myers , Kenji Watanabe , Takashi Taniguchi , Brian J. LeRoy

Bilayer graphene twisted at the angle of about 1.1{\deg} better known as magic angle, exhibits ultra-flat moir\'e superlattice bands that are a source of highly-tunable, exotic quantum phenomena. Such phenomena, like superconductivity,…

Strongly Correlated Electrons · Physics 2024-11-05 Giovanna Feraco , Wissem Boubaker , Petra Rudolf , Antonija Grubišić-Čabo

The possibility of superconducting pairing of electrons in doped graphene due to in-plane and out-of-plane phonons is studied. Quadratic coupling of electrons with out-of-plane phonons is considered in details, taking into account both…

Mesoscale and Nanoscale Physics · Physics 2010-05-27 Yu. E. Lozovik , A. A. Sokolik

We study the effect of electron-acoustic phonon interactions in twisted bilayer graphene on resistivity in the high-temperature transport and superconductivity in the low-temperature phase diagram. We theoretically show that twisted bilayer…

Mesoscale and Nanoscale Physics · Physics 2019-04-10 Fengcheng Wu , Euyheon Hwang , Sankar Das Sarma

We theoretically study the electronic structure of magic-angle twisted bilayer graphene with disordered moir\'e patterns. By using an extended continuum model incorporating non-uniform lattice distortion, we find that the local density of…

Mesoscale and Nanoscale Physics · Physics 2022-06-29 Naoto Nakatsuji , Mikito Koshino

Twisting bilayer sheets of graphene have been proven to be an efficient way to manipulate the electronic Dirac-like properties, resulting in flat bands at magic angles. Inspired by the electronic model, we develop a continuum model for the…

Materials Science · Physics 2023-09-20 Emmanuele Cappelluti , Jose Angel Silva-Guillén , Habib Rostami , Francisco Guinea

We show how to include the Jahn-Teller coupling of \mo phonons to the electrons in the continuum model formalism which describes small-angle twisted bilayer graphene. These phonons, which strongly couple to the valley degree of freedom, are…

Superconductivity · Physics 2020-07-03 M. Angeli , M. Fabrizio

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 present a theory of phonon-mediated superconductivity in near magic angle twisted bilayer graphene. Using a microscopic model for phonon coupling to moir\'e band electrons, we find that phonons generate attractive interactions in both…

Superconductivity · Physics 2018-12-19 Fengcheng Wu , A. H. MacDonald , Ivar Martin

Density functional perturbation theory is used to analyze electron-phonon interaction in bilayer graphene. The results show that phonon scattering in bilayer graphene bears more resemblance with bulk graphite than monolayer graphene. In…

Mesoscale and Nanoscale Physics · Physics 2010-11-29 K. M. Borysenko , J. T. Mullen , X. Li , Y. G. Semenov , J. M. Zavada , M. Buongiorno Nardelli , K. W. Kim

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 show that the electronic structure of the low-energy bands in the small angle-twisted bilayer graphene consists of a series of semi-metallic and topological phases. In particular we are able to prove, using an approximate low-energy…

Mesoscale and Nanoscale Physics · Physics 2019-07-24 Zhida Song , Zhijun Wang , Wujun Shi , Gang Li , Chen Fang , B. Andrei Bernevig

Moir\'e superlattice in twisted bilayer graphene has been proven to be a versatile platform for exploring exotic quantum phases. Extensive investigations have been invoked focusing on the zero-magnetic-field phase diagram at the magic twist…

The origin of superconductivity in twisted bilayer graphene -- whether phonon-driven or electron-driven -- remains unresolved, in part due to the absence of a quantitative and efficient model for electron-phonon coupling (EPC). In this…

Mesoscale and Nanoscale Physics · Physics 2026-02-12 Ziyan Zhu , Thomas P. Devereaux

We present a computational study of the phonon linewidths in twisted bilayer graphene arising from electron-phonon interactions and anharmonic effects. The electronic structure is calculated using distance-dependent transfer integrals based…

Mesoscale and Nanoscale Physics · Physics 2024-10-10 Shinjan Mandal , Indrajit Maity , H. R. Krishnamurthy , Manish Jain

Identifying the microscopic mechanism for superconductivity in magic-angle twisted bilayer graphene (MATBG) is an outstanding open problem. While MATBG exhibits a rich phase-diagram, driven partly by the strong interactions relative to the…

Superconductivity · Physics 2021-06-09 Cyprian Lewandowski , Debanjan Chowdhury , Jonathan Ruhman

Twisted graphene bilayers show a complex electronic structure, further modified by interaction effects. The main features can be obtained from effective models, which make use a few phenomenological parameters. We analyze the influence of…

Strongly Correlated Electrons · Physics 2019-03-04 Niels R. Walet , Francisco Guinea

Strong electron correlation and spin-orbit coupling (SOC) provide two non-trivial threads to condensed matter physics. When these two strands of physics come together, a plethora of quantum phenomena with novel topological order have been…

Mesoscale and Nanoscale Physics · Physics 2024-02-26 Jiang-Xiazi Lin , Ya-Hui Zhang , Erin Morissette , Zhi Wang , Song Liu , Daniel Rhodes , K. Watanabe , T. Taniguchi , James Hone , J. I. A. Li

A number of moir\'e graphene systems have nearly flat topological bands where electron motion is strongly correlated. Though microscopically these systems are only quasiperiodic, they can typically be treated as translation invariant to an…

Mesoscale and Nanoscale Physics · Physics 2021-03-10 Dan Mao , T. Senthil