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Flat-bands in magic angle twisted bilayer graphene (MATBG) have recently emerged as a rich platform to explore strong correlations, superconductivity and mag-netism. However, the phases of MATBG in magnetic field, and what they reveal about…

The discovery of magic angle twisted bilayer graphene (MATBG) has unveiled a rich variety of superconducting, magnetic and topologically nontrivial phases. The existence of all these phases in one material, and their tunability, has opened…

Mesoscale and Nanoscale Physics · Physics 2021-11-17 Petr Stepanov , Ming Xie , Takashi Taniguchi , Kenji Watanabe , Xiaobo Lu , Allan H. MacDonald , B. Andrei Bernevig , Dmitri K. Efetov

Moir\'e flatbands with high Chern numbers (C>1) offer opportunities to study the fractional quantum anomalous Hall effects that go beyond the Landau level paradigm with C=1, which remain unexplored yet. Here, we target the novel topological…

We outline an approach to endow a plain vanilla material with topological properties by creating topological bands in stacks of manifestly nontopological atomically thin materials. The approach is illustrated with a model system comprised…

Mesoscale and Nanoscale Physics · Physics 2015-09-22 Justin C. W. Song , Polnop Samutpraphoot , Leonid S. Levitov

Helical trilayer graphene realizes a versatile moir\'e system for exploring correlated topological states emerging from high Chern bands. Motivated by recent experimental observations of anomalous Hall effects at fractional fillings of…

Strongly Correlated Electrons · Physics 2025-10-02 Sen Niu , Jason Alicea , D. N. Sheng , Yang Peng

Chern insulators host topologically protected chiral edge currents with quantized conductance characterized by their Chern number. Switching the chirality of a Chern insulator, namely, the direction of the edge current, is highly…

Fractional Chern insulators (FCIs) showing a transport effect with fractionally quantized Hall plateaus emerging under zero magnetic field, provide a radically new opportunity to engineer topological quantum electronics. By construction of…

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

A striking example of frustration in physics is Hofstadter's butterfly, a fractal structure that emerges from the competition between a crystal's lattice periodicity and the magnetic length of an applied field. Current methods for…

Mesoscale and Nanoscale Physics · Physics 2025-03-04 Catalin D. Spataru , Wei Pan , Alexander Cerjan

Chern insulators, which are the lattice analogs of the quantum Hall states, can potentially manifest high-temperature topological orders at zero magnetic field to enable next-generation topological quantum devices. To date, integer Chern…

Many graphene moir\'e superlattices host narrow bands with non-zero valley Chern numbers. We provide analytical and numerical evidence for a robust spin and/or valley polarized insulator at total integer band filling in nearly flat bands of…

Strongly Correlated Electrons · Physics 2020-05-13 Cécile Repellin , Zhihuan Dong , Ya-Hui Zhang , T. Senthil

In two-dimensional materials where interacting Fermi pockets occur in valleys related by time-reversal symmetry, a spontaneous valley imbalance results in a novel state known as an orbital magnet. Due to the breaking of time-reversal…

Mesoscale and Nanoscale Physics · Physics 2026-05-18 Fernando Peñaranda , Fernando de Juan

We investigate the topological properties of photon-dressed energy bands in bilayer $\alpha-T_{3}$ lattices under off-resonant circularly polarized light, focusing on aligned and cyclic stacking configurations. Analytical expressions for…

Mesoscale and Nanoscale Physics · Physics 2025-11-06 O. Benhaida , E. H. Saidi , L. B. Drissi , R. Ahl Laamara

Combining field-theoretical methods and ab-initio calculations, we construct an effective Hamiltonian with a single giant-spin degree of freedom, capable of the describing the low-energy spin dynamics of ferromagnetic metal nanoclusters…

Other Condensed Matter · Physics 2010-01-28 T. O. Strandberg , C. M. Canali , A. H. MacDonald

Electrons of $d$-symmetry interacting with a localized non-collinear antiferromagnetic spin order on a kagome lattice are considered. Even in the absence of an external magnetic field, spin-orbit coupling or relativistic effects, the spin…

Mesoscale and Nanoscale Physics · Physics 2025-11-18 Waquar Ahmed , Steffen Schaeffer , Pierre Lombardo , Roland Hayn , Imam Makhfudz

It is known that three-dimensional magnetic systems with glide symmetry can be characterized by a $Z_2$ topological invariant together with the Chern number associated with the normal vector of the glide plane, and they are expressed in…

Mesoscale and Nanoscale Physics · Physics 2019-10-14 Heejae Kim , Ken Shiozaki , Shuichi Murakami

We study the collective excitation modes of the Chern insulator states in magic-angle twisted bilayer graphene aligned with hexagonal boron nitride (TBG/BN) at odd integer fillings ($\nu$) of the flat bands. For the $1 \times 1$…

Mesoscale and Nanoscale Physics · Physics 2023-06-07 Xianqing Lin , Quan Zhou , Cheng Li , Jun Ni

We propose the realization of a fractional Chern mosaic: a state characterized by a spatially varying topological order. This state is enabled by a separation of length scales that emerges when three graphene sheets are sequentially rotated…

Strongly Correlated Electrons · Physics 2024-11-14 Yves H. Kwan , Tixuan Tan , Trithep Devakul

Exploring the topological characteristics of electronic bands is essential in condensed matter physics. Moir\'e materials featuring flat bands provide a versatile platform for engineering band topology and correlation effects. In moir\'e…

Magnetic semimetals have increasingly emerged as lucrative platforms hosting spin-based topological phenomena in real and momentum spaces. Of particular interest is the emergence of Berry curvature, whose geometric origin, accessibility…

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