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Topological materials are quantum materials with nontrivial ground-state entanglement that are irremovable so long as certain rules, like invariance under symmetries and the existence of an energy gap, are respected. They showcase…

Mesoscale and Nanoscale Physics · Physics 2020-06-12 Hoi Chun Po

Flatness of discrete-time systems can be characterized by two simple properties. There exists a map, a submersion, from the flat coordinates and their forward shifts to the state and the input of the discrete-time system, such that the…

Differential Geometry · Mathematics 2023-03-10 Schlacher Kurt , Lindorfer Martin

We propose that light-matter coupling can be used to realize synthetic lattices. In particular, we consider a one-dimensional chain of exciton-photon sites to create a comb lattice that exhibits a transition from a flat band to a finite…

Mesoscale and Nanoscale Physics · Physics 2023-04-27 Amir Rahmani , Mateusz Kędziora , Andrzej Opala , Michał Matuszewski

In this work, we develop a systematic method of constructing flat-band models with and without band crossings. Our construction scheme utilizes the symmetry and spatial shape of a compact localized state (CLS) and also the singularity of…

Mesoscale and Nanoscale Physics · Physics 2021-08-26 Yoonseok Hwang , Jun-Won Rhim , Bohm-Jung Yang

We investigate, theoretically and experimentally, a photonic realization of a Sawtooth lattice. This special lattice exhibits two spectral bands, with one of them experiencing a complete collapse to a highly degenerate flat band for a…

After the discovery of graphene and its many fascinating properties, there has been a growing interest for the study of "artificial graphenes". These are totally different and novel systems which bear exciting similarities with graphene.…

Mesoscale and Nanoscale Physics · Physics 2019-06-20 Gilles Montambaux

Certain tight binding lattices host macroscopically degenerate flat spectral bands. Their origin is rooted in local symmetries of the lattice, with destructive interference leading to the existence of compact localized eigenstates. We study…

Disordered Systems and Neural Networks · Physics 2017-01-13 Daniel Leykam , Joshua D. Bodyfelt , Anton S. Desyatnikov , Sergej Flach

Magic-angle twisted bilayer graphene (MATBG) exhibits correlated phenomena such as superconductivity and Mott insulating state related to the weakly dispersing flat band near the Fermi energy. Beyond its moir\'e period, such flat band is…

We study the effect of twisting on bilayer graphene. The effect of lattice relaxation is included; we look at the electronic structure, piezo-electric charges and spontaneous polarisation. We show that the electronic structure without…

Mesoscale and Nanoscale Physics · Physics 2021-03-31 Niels R. Walet , Francisco Guinea

We present the Stagome lattice, a variant of the Kagome lattice, where one can make any of the bands completely flat by tuning an externally controllable magnetic flux. This systematically allows the energy of the flat band to coincide with…

Strongly Correlated Electrons · Physics 2025-03-03 Biplab Pal , Georges Bouzerar

The Hubbard model of bosons on two dimensional lattices with a lowest flat band is discussed. In these systems there is a critical density, where the ground state is known exactly and can be represented as a charge density wave. Above this…

Quantum Gases · Physics 2015-08-18 Petra Pudleiner , Andreas Mielke

Flat bands imply lack of itinerancy due to some constraints that, in principle, results in anomalous behaviors with randomness. By a molecular orbital (MO) representation of the flat band systems, random MO models are introduced where the…

Disordered Systems and Neural Networks · Physics 2022-01-05 Yasuhiro Hatsugai

Flatbands emerge from a myriad of structures such as Landau levels, Lieb and Kagome lattices, linegraphs, and more recently moire superlattices. They enable unique properties including slow light in photonics, correlated phases in…

Quantum materials constitute a novel category of substances wherein quantum effects and electron-electron (e-e) interactions give rise to unforeseen phenomena on a macroscopic scale. Of particular interest within the realm of quantum…

The discovery of superconductivity in twisted bilayer graphene has triggered a resurgence of interest in flat-band superconductivity. Here, we investigate the square-octagon lattice, which also exhibits two perfectly flat bands when…

Superconductivity · Physics 2020-07-08 Lizardo H. C. M. Nunes , Cristiane Morais Smith

The origin of many quantum-material phenomena is intimately related to the presence of flat electronic bands. In quantum simulation, such bands have been realized through line-graph lattices, a class of lattices known to exhibit flat bands.…

Strongly Correlated Electrons · Physics 2022-05-23 Christie S. Chiu , Annette N. Carroll , Nicolas Regnault , Andrew A. Houck

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

We demonstrate a nonradiative flat band for spoof surface plasmon polaritons bounded on a structured surface with Lieb lattice symmetry in the terahertz regime. First, we theoretically derive the dispersion relation of spoof plasmons in a…

Artificial electronic lattices, created atom by atom in a scanning tunneling microscope, have emerged as a highly tunable platform to realize and characterize the lowest-energy bands of novel lattice geometries. Here, we show that…