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We develop a two stage renormalization group which connects the continuum Hamiltonian for twisted bilayer graphene at length scales shorter than the moire superlattice period to the Hamiltonian for the active narrow bands only which is…

Strongly Correlated Electrons · Physics 2020-12-21 Oskar Vafek , Jian Kang

We provide a formal derivation of a reduced model for twisted bilayer graphene (TBG) from Density Functional Theory. Our derivation is based on a variational approximation of the TBG Kohn-Sham Hamiltonian and asymptotic limit techniques. In…

Mesoscale and Nanoscale Physics · Physics 2023-04-14 Eric Cancès , Louis Garrigue , David Gontier

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

Close to a magical angle, twisted bilayer graphene (TBLG) systems exhibit isolated flat electronic bands and, accordingly, strong electron localization. TBLGs have hence been ideal platforms to explore superconductivity, correlated…

Mesoscale and Nanoscale Physics · Physics 2021-05-28 V. Hung Nguyen , D. Paszko , M. Lamparski , B. Van Troeye , V. Meunier , J. -C. Charlier

Magic-angle twisted bilayer graphene (TBG), with rotational misalignment close to 1.1$^\circ$, features isolated flat electronic bands that host a rich phase diagram of correlated insulating, superconducting, ferromagnetic, and topological…

The discovery of superconducting and insulating states in magic angle twisted bilayer graphene (MATBG) has ignited considerable interest in understanding the nature of electronic interactions in this chemically pristine material system. The…

Mesoscale and Nanoscale Physics · Physics 2019-08-02 Yonglong Xie , Biao Lian , Berthold Jäck , Xiaomeng Liu , Cheng-Li Chiu , Kenji Watanabe , Takashi Taniguchi , B. Andrei Bernevig , Ali Yazdani

Superlattices from twisted graphene mono- and bi-layer systems give rise to on-demand many-body states such as Mott insulators and unconventional superconductors. These phenomena are ascribed to a combination of flat bands and strong…

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

One of the most remarkable theoretical findings in magic angle twisted bilayer graphene (TBG) is the emergence of ferromagnetic Slater determinants as exact ground states for the interacting Hamiltonian at the chiral limit. This discovery…

Mathematical Physics · Physics 2025-06-02 Simon Becker , Lin Lin , Kevin D. Stubbs

Twisted bilayer graphene (TBG) is remarkable for its topological flat bands, which drive strongly-interacting physics at integer fillings, and its simple theoretical description facilitated by the Bistritzer-MacDonald Hamiltonian, a…

Strongly Correlated Electrons · Physics 2022-08-10 Jonah Herzog-Arbeitman , Aaron Chew , Dmitri K. Efetov , B. Andrei Bernevig

The linear perturbation group transformation (LPRG) is used to study the thermodynamics of the axial next-nearest-neighbor Ising model with four spin interactions (extended ANNNI) in a field. The LPRG for weakly interacting Ising chains is…

Statistical Mechanics · Physics 2013-03-25 J. Sznajd

We propose that the electronic structure of twisted bilayer graphene (TBG) can be understood as Dirac fermions coupled with opposite pseudo magnetic fields generated by the moir\'e pattern. The two low-energy flat bands from each monolayer…

Mesoscale and Nanoscale Physics · Physics 2019-04-24 Jianpeng Liu , Junwei Liu , Xi Dai

We implement a self-consistent Hartree-Fock approximation based on a microscopic model in real space, which allows us to consider the interplay between the Hubbard and the extended Coulomb interaction in twisted bilayer graphene at the…

Mesoscale and Nanoscale Physics · Physics 2021-09-15 J. Gonzalez , T. Stauber

Moir\'e materials, and in particular twisted bilayer graphene (TBG), exhibit a range of fascinating phenomena, that emerge from the interplay of band topology and interactions. We show that the non-linear second-order photoresponse is an…

Mesoscale and Nanoscale Physics · Physics 2021-07-21 Swati Chaudhary , Cyprian Lewandowski , Gil Refael

We review the theoretical modelling of moir\'e materials, focusing on various aspects of magic-angle twisted bilayer graphene (MA-TBG) viewed through the lens of Hartree-Fock mean-field theory. We first provide an elementary introduction to…

Strongly Correlated Electrons · Physics 2026-03-20 Yves H. Kwan , Ziwei Wang , Glenn Wagner , Nick Bultinck , Steven H. Simon , Siddharth A. Parameswaran

In the vicinity of the magic angle in twisted bilayer graphene (TBG), the two low-energy van Hove singularities (VHSs) become exceedingly narrow1-10 and many exotic correlated states, such as superconductivity, ferromagnetism, and…

Strongly Correlated Electrons · Physics 2020-02-25 Yu Zhang , Zhe Hou , Ya-Xin Zhao , Zi-Han Guo , Yi-Wen Liu , Si-Yu Li , Ya-Ning Ren , Qing-Feng Sun , Lin He

We consider renormalization group (RG) transformations for classical Ising-type lattice spin systems in the infinite volume limit. Formally, the RG maps a Hamiltonian H into a renormalized Hamiltonian H': exp(-H'(\sigma'))=\sum_\sigma…

Mathematical Physics · Physics 2012-05-04 Mei Yin

We derive a novel computational scheme for functional Renormalization Group (fRG) calculations for interacting fermions on 2D lattices. The scheme is based on the exchange parametrization fRG for the two-fermion interaction, with additional…

Strongly Correlated Electrons · Physics 2017-03-08 J. Lichtenstein , D. Sánchez de la Peña , D. Rohe , E. Di Napoli , C. Honerkamp , S. A. Maier

We present a unified framework for the renormalisation of the Hamiltonian and eigenbasis of a system of correlated electrons, unveiling thereby the interplay between electronic correlations and many-particle entanglement. For this, we…

Strongly Correlated Electrons · Physics 2021-10-25 Anirban Mukherjee , Siddhartha Lal

In a groundbreaking experimental advance it was recently shown that by stacking two sheets of graphene atop of each other at a twist angle close to one of the so called "magic angles", an effective two-dimensional correlated system emerges.…

Mesoscale and Nanoscale Physics · Physics 2019-10-01 Lede Xian , Dante M. Kennes , Nicolas Tancogne-Dejean , Massimo Altarelli , Angel Rubio
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