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We investigate the competition between acoustic-phonon-mediated superconductivity and the long-range Coulomb interaction in moir\'eless graphene multilayers, specifically, Bernal bilayer graphene, rhombohedral trilayer graphene, and…

Superconductivity · Physics 2022-07-11 Yang-Zhi Chou , Fengcheng Wu , Jay D. Sau , Sankar Das Sarma

Effects of short-range correlations on the Coulomb screening, the phonons, and the pairing interactions are examined in electron-phonon systems. First, we derive a model Hamiltonian of Coulomb interactions which includes both the long-range…

Superconductivity · Physics 2007-05-23 Hiroshi Shimahara

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

We study the symmetries of twisted trilayer graphene's band structure under various extrinsic perturbations, and analyze the role of long-range electron-electron interactions near the first magic angle. The electronic structure is modified…

Mesoscale and Nanoscale Physics · Physics 2021-10-04 Vo Tien Phong , Pierre A. Pantaleón , Tommaso Cea , Francisco Guinea

We analyze the phase diagram of twisted graphene bilayers near a magic angle. We consider the effect of the long range Coulomb interaction, treated within the self consistent Hartree-Fock approximation, and we study arbitrary band fillings.…

Strongly Correlated Electrons · Physics 2020-07-15 Tommaso Cea , Francisco Guinea

Recent experiments on twisted bilayer graphene show the urgent need for establishing a low-energy lattice model for the system. We use the constrained random phase approximation to study the interaction parameters of such models taking into…

Strongly Correlated Electrons · Physics 2020-08-05 Tuomas I. Vanhala , Lode Pollet

By comparing with recently available experimental data from several groups, we critically discuss the manifestation of continuum many body interaction effects in twisted bilayer graphene (tBLG) with small twist angles and low carrier…

Mesoscale and Nanoscale Physics · Physics 2020-06-02 Sankar Das Sarma , Fengcheng Wu

We propose a theory for how the weak phonon-mediated interaction ($J_{\rm A}\!=\!1\!\sim\!4$meV) wins over the prohibitive Coulomb repulsion ($U\!=\!30\!\sim\!60$meV) and leads to a superconductor in magic-angle twisted bilayer graphene…

Superconductivity · Physics 2024-10-03 Yi-Jie Wang , Geng-Dong Zhou , Shi-Yu Peng , Biao Lian , Zhi-Da Song

By using the first-principles method based on density of functional theory, we study the electronic properties of twisted bilayer graphene with some specific twist angles and interlayer spacings. With the decrease of the twist angle(the…

Mesoscale and Nanoscale Physics · Physics 2019-04-05 Xun-Wang Yan , Jing Li , Yanyun Wang , Miao Gao

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

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

Graphene moire superlattices are outstanding platforms to study correlated electron physics and superconductivity with exceptional tunability. However, robust superconductivity has been measured only in magic-angle twisted bilayer graphene…

Mesoscale and Nanoscale Physics · Physics 2021-10-20 Young Woo Choi , Hyoung Joon Choi

Understanding and tuning correlated states is of great interest and significance to modern condensed matter physics. The recent discovery of unconventional superconductivity and Mott-like insulating states in magic-angle twisted bilayer…

The quest for unconventional superconductivity governed by Coulomb repulsion between electrons rather than phonon attraction received new momentum with the advent of moir\'e graphene. Initially, delineating the phonon and…

Superconductivity · Physics 2023-05-24 Zhiyu Dong , Andrey V. Chubukov , Leonid Levitov

Motivated by the recent experimental detection of superconductivity in Bernal bilayer (AB) and rhombohedral trilayer (ABC) graphene, we study the emergence of superconductivity in multilayer graphene based on a Kohn-Luttinger (KL)-like…

Mesoscale and Nanoscale Physics · Physics 2024-02-01 Ziyan Li , Xueheng Kuang , Alejandro Jimeno-Pozo , Héctor Sainz-Cruz , Zhen Zhan , Shengjun Yuan , Francisco Guinea

The effects of Coulomb interactions on the electronic properties of bilayer graphene nanoribbons (BGNs) covered by a gate electrode are studied theoretically. The electron density distribution and the potential profile are calculated…

Mesoscale and Nanoscale Physics · Physics 2015-05-19 Hengyi Xu , T. Heinzel , A. A. Shylau , I. V. Zozoulenko

Recent observations of superconductivity in Moire graphene have lead to an intense interest in that system, with subsequent studies revealing a more complex phase diagram including correlated insulators and ferromagnetic phases. Here we…

Strongly Correlated Electrons · Physics 2023-05-10 Z. E. Krix , O. P. Sushkov

Coulomb drag between parallel quantum wells provides a uniquely sensitive measurement of electron correlations since the drag response depends on interactions only. Recently it has been demonstrated that a new regime of strong interactions…

Mesoscale and Nanoscale Physics · Physics 2016-07-20 J. I. A. Li , T. Taniguchi , K. Watanabe , J. Hone , A. Levchenko , C. R. Dean

Strongly correlated phases in twisted bilayer graphene (TBG) typically arise as transitions from a state in which the system behaves as a normal metal. In such metallic regime, electron-electron interactions usually only play a subleading…

Mesoscale and Nanoscale Physics · Physics 2023-10-17 Federico Escudero , Juan Sebastián Ardenghi

We investigate the domain wall network in twisted bilayer graphene (TBG) under the influence of interlayer bias and screening effect from the layered structure. Starting from the continuum model, we analyze the low-energy domain wall modes…

Mesoscale and Nanoscale Physics · Physics 2024-07-22 Hao-Chien Wang , Chen-Hsuan Hsu