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Moir\'e systems have emerged in recent years as a rich platform to study strong correlations. Here, we will discuss a simple, experimentally feasible setup based on periodically strained graphene that reproduces several key aspects of…

Mesoscale and Nanoscale Physics · Physics 2022-11-03 Qiang Gao , Junkai Dong , Patrick Ledwith , Daniel Parker , Eslam Khalaf

We consider graphene bilayer in a constant magnetic field of arbitrary orientation (i.e. tilted with respect to the graphene plane). In the low energy approximation to tight binding model with Peierls substitution, we find the exact…

Mesoscale and Nanoscale Physics · Physics 2010-08-04 Young-Hwan Hyun , Yoonbai Kim , Corneliu Sochichiu , Min-Young Choi

We elaborate the first theoretical realization of two dimensional itinerant topological magnons, based on the quarter filled Haldane-Hubbard model with a nearly-flat electron band. By using the exact diagonalization method with a projection…

Strongly Correlated Electrons · Physics 2019-08-27 Zhao-Long Gu , Zhao-Yang Dong , Shun-Li Yu , Jian-Xin Li

We propose an exact analytical decimation transformation scheme to explore the fascinating coexistence of flat bands and Dirac fermions in three-dimensional coupled kagome systems. Our method allows coarse-graining of the parameter space…

Materials Science · Physics 2023-11-08 Anumita Bose , Arka Bandyopadhyay , Awadhesh Narayan

We fully characterize the eigenvalues (flat bands) of the maximal abelian cover of a finite multi-graph in terms of the combinatorics of the base graph. This solves a problem of Higuchi and Nomura (2009, Problem 6.11). We use our new…

Spectral Theory · Mathematics 2025-08-26 Wenbo Li , Michael Magee , Mostafa Sabri , Joe Thomas

The existence of Bloch flat bands provides an facile pathway to realize strongly correlated phenomena in materials. Using density-functional theory and tight-binding approach, we show that the flat bands can form in twisted bilayer of…

Materials Science · Physics 2020-03-04 Xing-Ju Zhao , Yang Yang , Dong-Bo Zhang , Su-Huai Wei

Flat bands play an important role in the study of strongly correlated phenomena, such as ferromagnetism, superconductivity, and fractional quantum Hall effect. Here we report direct experimental evidence for the presence of flat bands,…

Mesoscale and Nanoscale Physics · Physics 2012-09-28 Lei Feng , Xianqing Lin , Lan Meng , Jia-Cai Nie , Jun Ni , Lin He

Monolayer graphene placed with a twist on top of AB-stacked bilayer graphene hosts topological flat bands in a wide range of twist angles. The dispersion of these bands and gaps between them can be efficiently controlled by a perpendicular…

Strongly Correlated Electrons · Physics 2020-08-05 Louk Rademaker , Ivan Protopopov , Dmitry Abanin

Atomically thin crystals hosting flat electronic bands have been recently identified as a rich playground for exploring and engineering strongly correlated phases. Yet, their variety remains limited, primarily to two-dimensional moir\'e…

Mesoscale and Nanoscale Physics · Physics 2024-12-23 Ruize Ma , Nikita V. Tepliakov , Arash A. Mostofi , Michele Pizzochero

When atomically thin two-dimensional (2D) materials are layered they often form incommensurate non-crystalline structures that exhibit long-period moir{\' e} patterns when examined by scanning probes. In this paper we present an approach…

Mesoscale and Nanoscale Physics · Physics 2015-02-23 Jeil Jung , Arnaud Raoux , Zhenhua Qiao , Allan H. MacDonald

We propose Landau levels as a probe for the topological character of electronic bands in two-dimensional moir\'e superlattices. We consider two configurations of twisted double bilayer graphene (TDBG) that have very similar band structures,…

Mesoscale and Nanoscale Physics · Physics 2021-02-10 QuanSheng Wu , Jianpeng Liu , Oleg V. Yazyev

We formulate the chiral decomposition rules that govern the electronic structure of a broad family of twisted $N+M$ multilayer graphene configurations that combine arbitrary stacking order and a mutual twist. We show that at the magic angle…

Mesoscale and Nanoscale Physics · Physics 2024-03-20 ShengNan Zhang , Bo Xie , QuanSheng Wu , Jianpeng Liu , Oleg V. Yazyev

Using the method developed in the companion paper, we construct the effective continuum theories for two different microscopic tight binding models of the twisted bilayer graphene at the twist angle of $1.05^\circ$, one Slater-Koster based…

Strongly Correlated Electrons · Physics 2023-02-24 Jian Kang , Oskar Vafek

We elaborate that single-layer graphene with periodic vacancies can have a band structure containing nodal lines or nodal loops, opening the possibility of graphene-based electronic or spintronic devices with novel functionalities. The…

Mesoscale and Nanoscale Physics · Physics 2022-05-30 Matheus S. M. de Sousa , Fujun Liu , Mariana Malard , Fanyao Qu , Wei Chen

The rise of moir\'{e} materials has led to experimental realizations of integer and fractional Chern insulators in small or vanishing magnetic fields. At the same time, a set of minimal conditions sufficient to guarantee a Abelian…

Mesoscale and Nanoscale Physics · Physics 2025-06-23 Manato Fujimoto , Daniel E. Parker , Junkai Dong , Eslam Khalaf , Ashvin Vishwanath , Patrick Ledwith

Recently, artificial moire superlattices of classical waves have aroused tremendous interest, inspired by the newly emergent twistronics that focuses on the peculiar electronic properties induced by flat bands. However, so far, the moire…

Materials Science · Physics 2021-12-28 Tingzhi Liu , Xingjian Zhang , Qicheng Zhang , Xiying Fan , Fengcheng Wu , Chunyin Qiu

Theory of spin-orbit coupling in bilayer graphene is presented. The electronic band structure of the AB bilayer in the presence of spin-orbit coupling and a transverse electric field is calculated from first-principles using the linearized…

Mesoscale and Nanoscale Physics · Physics 2012-03-28 Sergej Konschuh , Martin Gmitra , Denis Kochan , Jaroslav Fabian

Dispersionless flat bands are proposed to be a fundamental ingredient to achieve the various sought after quantum states of matter including high-temperature superconductivity1-4 and fractional quantum Hall effect5-6. Materials with such…

We address in this work the question of the discretization of two-dimensional periodic Dirac Hamiltonians. Standard finite differences methods on rectangular grids are plagued with the so-called Fermion doubling problem, which creates…

Computational Physics · Physics 2020-06-01 H. Chen , O. Pinaud , M. Tahir

Defining chiral lattice gauge theories in the Ginsparg-Wilson formalism is complicated by the so-called fermion measure problem. It has been proven for the abelian theories that smooth well-behaved fermion measure exists if and only if the…

High Energy Physics - Lattice · Physics 2013-04-11 Yanwen Shang