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The observation of delicate correlated phases in twisted heterostructures of graphene and transition metal dichalcogenides suggests that moir\'e flat bands are intrinsically resilient against certain types of disorder. Here, we investigate…

Mesoscale and Nanoscale Physics · Physics 2025-07-22 Valentin Crépel , Peize Ding , Nishchhal Verma , Nicolas Regnault , Raquel Queiroz

Flat bands - single-particle energy bands - in tight-binding networks have attracted attention due to the presence of macroscopic degeneracies and their extreme sensitivity to perturbations. This makes them natural candidates for emerging…

Optics · Physics 2024-03-27 Carlo Danieli , Alexei Andreanov , Daniel Leykam , Sergej Flach

We demonstrate that a complete class of flat-band lattices with underlying commutative local symmetries exhibit a locally fragmented Hilbert space. The equitable partition theorem ensures distinct parities for the compact localized states…

Statistical Mechanics · Physics 2025-04-11 Eloi Nicolau , Anselmo M. Marques , Ricardo G. Dias , Verònica Ahufinger

We review recent progresses in the study of flat band systems, especially focusing on the fundamental physics related to the singularity of the flat band's Bloch wave functions. We first explain that the flat bands can be classified into…

Optics · Physics 2020-12-09 Jun-Won Rhim , Bohm-Jung Yang

Certain lattice wave systems in translationally invariant settings have one or more spectral bands that are strictly flat or independent of momentum in the tight binding approximation, arising from either internal symmetries or fine-tuned…

Mesoscale and Nanoscale Physics · Physics 2018-06-07 Daniel Leykam , Alexei Andreanov , Sergej Flach

The conditions leading to flat dispersionless frequency bands in truly one-dimensional parity-time ($\cal PT$) symmetric metamaterials comprising split-ring resonators (SRRs) arranged in a binary pattern are obtained analytically. In this…

Optics · Physics 2020-05-13 N. Lazarides , G. P. Tsironis

Hermitian bipartite models are characterized by the presence of chiral symmetry and by Lieb's theorem, which derives the number of zero-energy flat bands of the model from the imbalance of sites between its two sublattices. Here, we…

Other Condensed Matter · Physics 2022-11-29 A. M. Marques , R. G. Dias

Flat energy bands of model lattice Hamiltonians provide a key ingredient in designing dispersionless wave excitations and have become a versatile platform to study various aspects of interacting many-body systems. Their essential merit lies…

Mesoscale and Nanoscale Physics · Physics 2021-07-15 C. V. Morfonios , M. Röntgen , M. Pyzh , P. Schmelcher

We study non-Hermitian photonic lattices that exhibit competition between conservative and non-Hermitian (gain/loss) couplings. A bipartite sublattice symmetry enforces the existence of non-Hermitian flat bands, which are typically embedded…

Optics · Physics 2017-08-30 Daniel Leykam , Sergej Flach , Y. D. Chong

Here we report on several anomalies in quantum transport at the band center of a bipartite lattice with vacancies that are surely due to its chiral symmetry, namely: no weak localization effect shows up, and, when leads have a single…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 G. Chiappe , E. Louis , M. J. Sanchez , J. A. Verges

We derive symmetry-based conditions for tight-binding Hamiltonians with flatbands to have compact localized eigenstates occupying a single unit cell. The conditions are based on unitary operators commuting with the Hamiltonian and…

Mesoscale and Nanoscale Physics · Physics 2024-11-26 Jung-Wan Ryu , Alexei Andreanov , Hee Chul Park , Jae-Ho Han

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

Flat bands provide a natural platform for emergent electronic states beyond Landau paradigm. Among those of particular importance are flat Chern bands, including bands of higher Chern numbers ($C$$>$$1$). We introduce a new framework for…

Strongly Correlated Electrons · Physics 2022-10-04 Alexander Kruchkov

Flat bands in lattice models have provided useful platforms for studying strong correlation and topological physics. Recently, honeycomb superlattices have been shown to host flat bands that persist in the presence of local perturbations…

Mesoscale and Nanoscale Physics · Physics 2020-12-15 Zihao Qi , Eric Bobrow , Yi Li

Band theory provides the foundation for understanding electronic structure in crystalline materials, but its reliance on exact translational symmetry limits its applicability to systems with defects, disorder, incommensurate modulations, or…

Materials Science · Physics 2026-05-08 Christopher A. Bairnsfather , Ralph M. Kaufmann , Terry A. Loring , Alexander Cerjan

We report the existence of \emph{flat bands} in a p-wave superconducting Kitaev ladder. We identify two sets of parameters for which the Kitaev ladder sustains flat bands. These flat bands are accompanied by highly localized eigenstates…

Mesoscale and Nanoscale Physics · Physics 2020-02-24 Ritu Nehra , Devendra Singh Bhakuni , Ajith Ramachandran , Auditya Sharma

We consider localisation problems belonging to the chiral symmetry classes, in which sublattice symmetry is responsible for singular behaviour at a band centre. We formulate models which have the relevant symmetries and which are…

Mesoscale and Nanoscale Physics · Physics 2013-05-29 Marc Bocquet , J. T. Chalker

Systems hosting flat bands offer a powerful platform for exploring strong correlation physics. Theoretically topological degeneracy rising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate…

Superconductivity · Physics 2026-01-07 Yuge Chen , Hui Yu , Yun-Peng Huang , Zhen-Yu Zheng , Jiangping Hu

Electronic flat bands have localized Wannier-like orbitals as zero modes. In the Lieb or the kagome models, the localized orbitals satisfy a topological condition that entails two non-contractible loop eigenstates along $x/y$-axis in real…

Mesoscale and Nanoscale Physics · Physics 2026-03-27 Rui-Heng Liu , Jiangping Hu , Chen Fang

Periodic photonic structures enable precise control over the light-matter interaction through band structure engineering. Certain lattice geometries exhibit dispersionless flat bands, characterized by vanishing group velocity and diverging…