Detangling flat bands into Fano lattices

Flach, Sergej; Leykam, Daniel; Bodyfelt, Joshua D.; Matthies, Peter; Desyatnikov, Anton S.

doi:10.1209/0295-5075/105/30001

Cited by 218 publications

(268 citation statements)

References 43 publications

(57 reference statements)

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“…One interesting consequence of a flat band is the different scaling properties of its localization length when compared with a dispersive band [18][19][20], due to a multitude of degenerate states in the flat band. This degeneracy has another important implication on Parity-Time (PT ) symmetry breaking [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]: it was found recently that the degeneracy of the underlying Hermitian spectrum, before any T -breaking perturbations are introduced, determines whether thresholdless PT symmetry breaking is possible [40].…”

Section: Introductionmentioning

confidence: 99%

Parity-time symmetry in a flat-band system

2015

Phys. Rev. A

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In this paper we introduce Parity-Time (PT ) symmetric perturbation to a one-dimensional Lieb lattice, which is otherwise P-symmetric and has a flat band. In the flat band there are a multitude of degenerate dark states, and the degeneracy N increases with the system size. We show that the degeneracy in the flat band is completely lifted due to the non-Hermitian perturbation in general, but it is partially maintained with the half-gain-half-loss perturbation and its "V" variant that we consider. With these perturbations, we show that both randomly positioned states and pinned states at the symmetry plane in the flat band can undergo thresholdless PT breaking. They are distinguished by their different rates of acquiring non-Hermicity as the PT -symmetric perturbation grows, which are insensitive to the system size. Using a degenerate perturbation theory, we derive analytically the rate for the pinned states, whose spatial profiles are also insensitive to the system size. Finally, we find that the presence of weak disorder has a strong effect on modes in the dispersive bands but not on those in the flat band. The latter respond in completely different ways to the growing PT -symmetric perturbation, depending on whether they are randomly positioned or pinned.

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Section: Introductionmentioning

confidence: 99%

Parity-time symmetry in a flat-band system

2015

Phys. Rev. A

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“…This picture changes if long-range disorder is included in the model, as it has been studied to explain the Kondo effect in defective graphene 44 and Fano resonances in Lieb-like optical lattices 45 . Long-range disorder is ubiquitous in graphene samples.…”

Section: A Mapping Onto the Anderson Hamiltonianmentioning

confidence: 99%

Spin relaxation in disordered graphene: Interplay between puddles and defect-induced magnetism

Miranda

Mucciolo

Lewenkopf

2019

Journal of Physics and Chemistry of Solids

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We study the spin relaxation in graphene due to magnetic moments induced by defects. We propose and employ in our studies a microscopic model that describes magnetic impurity scattering processes mediated by charge puddles. This model incorporates the spin texture related to the defect-induced state. We calibrate our model parameters using experimentally-inferred values. The results we obtain for the spin relaxation times are in very good agreement with experimental findings. Our study leads to a comprehensive explanation for the short spin relaxation times reported in the experimental literature. We also propose a new interpretation for the puzzling experimental observation of enhanced spin relaxation times in hydrogenated graphene samples in terms of a combined effect due to disorder configurations that lead to an increased coupling to the magnetic moments and the tunability of the defect-induced π-like magnetism in graphene.

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“…They feature different local symmetry and topology properties, and can be classified according to the number U of unit cells which they occupy [5]. Perturbations may hybridize CLSs with dispersive states through a spatially local resonant scenario [5], similar to Fano resonances [6]. The CLS existence has been experimentally probed in the same settings where FB lattices may be realized, as mentioned above: waveguiding arrays [7][8][9], exciton-polariton condensates [10], and atomic BECs [4].…”

Section: Introductionmentioning

confidence: 99%

“…Here we study the existence of nonlinear localized modes in a pseudospinor (two-component) diamond chain, whose components are linearly mixed due to spin-orbit-coupling (SOC). The system can be implemented using a binary Bose-Einstein condensate (BEC) trapped in an optically imprinted potential emulating, e.g., the "diamond chain" [5]. The two components represent different atomic states, and the SOC interaction between them can be induced by means of a recently elaborated technique, making use of properly applied external magnetic and optical fields [19].…”

Section: Introductionmentioning

confidence: 99%

Nonlinear localized flat-band modes with spin-orbit coupling

et al. 2016

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We report the coexistence and properties of stable compact localized states (CLSs) and discrete solitons (DSs) for nonlinear spinor waves on a flatband network with spin-orbit coupling (SOC). The system can be implemented by means of a binary Bose-Einstein condensate loaded in the corresponding optical lattice. In the linear limit, the SOC opens a minigap between flat and dispersive bands in the system's bandgap structure, and preserves the existence of CLSs at the flatband frequency, simultaneously lowering their symmetry. Adding onsite cubic nonlinearity, the CLSs persist and remain available in an exact analytical form, with frequencies which are smoothly tuned into the minigap. Inside of the minigap, the CLS and DS families are stable in narrow areas adjacent to the FB. Deep inside the semi-infinite gap, both the CLSs and DSs are stable too.

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Detangling flat bands into Fano lattices

Cited by 218 publications

References 43 publications

Parity-time symmetry in a flat-band system

Parity-time symmetry in a flat-band system

Spin relaxation in disordered graphene: Interplay between puddles and defect-induced magnetism

Nonlinear localized flat-band modes with spin-orbit coupling

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