Dynamics of Frenkel Excitons in Pentacene

Gombar, Sonja; Mali, Petar; Pantić, M.; Pavkov-Hrvojević, Milica; Radošević, Slobodan

doi:10.3390/ma11112219

Cited by 4 publications

(22 citation statements)

References 42 publications

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“…Thus one can understand the first increase of the ladder of Shapiro steps in Figures of Ref. [15], see Sect. 5.2 below.…”

Section: The Overdamped Langevin Equationmentioning

confidence: 88%

“…In Sect. 4, the case of the spring potential with N =8 chain length [2,15] and k/v = 1/4 soft springs is discussed. Using the tool of NTs we explore the many 'floors' of the PES of the 8-chain.…”

Section: Supplementary Informationmentioning

confidence: 99%

“…In numerical tests, we scale the a s -constant of the Ppotential to 2π for computational simplicity. We fix the potential constants v = 1 and k = 1/4 and use a short chain with N = 8 particles [2,15]. We treat a simple special case of the FK model with a s = 2 a o with misfit 1/2 between the two potentials.…”

Section: The Fk Modelmentioning

confidence: 99%

“…In Ref. [15], and many other references, the unspecific washboard force direction l=1/ √ N (1,1,...,1) for the external force is used throughout. Thus, the force acts on all particles to the same amount.…”

Section: A 'Global' Nt To Unit Direction F=1/mentioning

confidence: 99%

“…If we put the gradient components to zero, we get the ansatz of the NT theory described in the former section. In contrast, one may use them on the right-hand side of an overdamped Langevin equation [2,15]…”

Section: The Overdamped Langevin Equationmentioning

confidence: 99%

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Description of Shapiro steps on the potential energy surface of a Frenkel–Kontorova model, Part II: free boundaries of the chain

Quapp

Bofill

2021

Eur. Phys. J. B

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We explain Shapiro steps in a Frenkel–Kontorova (FK) model for a 1D chain of particles with free boundaries. The action of an external alternating force for the oscillating structure of the chain is important here. The different ’floors’ of the potential energy surface (PES) of this model play an important role. They are regions of kinks, double kinks, and so on. We will find out that the preferable movements are the sliding of kinks or antikinks through the chain. The more kinks / antikinks are included the higher is the ’floor’ through the PES. We find the Shapiro steps moving and oscillating anywhere between the floors. They start with a single jump over the highest SP in the global valley through the PES, like in part I of this series. They finish with complicated oscillations in the PES, for excitations directly over the critical depinning force. We use an FK model with free boundary conditions. In contrast to other results in the past, for this model, we obtain Shapiro steps in an unexpected, inverse sequence. We demonstrate Shapiro steps for a case with soft ’springs’ between an 8-particle FK chain. Graphic abstract

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“…Thus one can understand the first increase of the ladder of Shapiro steps in Figures of Ref. [15], see Sect. 5.2 below.…”

Section: The Overdamped Langevin Equationmentioning

confidence: 88%

Section: Supplementary Informationmentioning

confidence: 99%

Section: The Fk Modelmentioning

confidence: 99%

Section: A 'Global' Nt To Unit Direction F=1/mentioning

confidence: 99%

Section: The Overdamped Langevin Equationmentioning

confidence: 99%

See 3 more Smart Citations

Description of Shapiro steps on the potential energy surface of a Frenkel–Kontorova model, Part II: free boundaries of the chain

Quapp

Bofill

2021

Eur. Phys. J. B

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Exciton dynamics in different aromatic hydrocarbon systems*

Rutonjski¹,

Mali²,

Radošević³

et al. 2020

Chinese Phys. B

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The exciton dispersion is examined in the case of four selected prototypical molecular solids: pentacene, tetracene, picene, and chrysene. The model parameters are determined by fitting to experimental data obtained by inelastic electron scattering. Within the picture that relies on Frenkel-type excitons we obtain that theoretical dispersion curves along different directions in the Brillouin zone are in good agreement with the experimental data, suggesting that the influence of charge-transfer excitons on exciton dispersion of the analyzed organic solids is not as large as proposed. In reciprocal space directions where Davydov splitting is observed we employ the upgraded version of Hamiltonian used in Materials 11, 2219 (2018).

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Nature of Excitons and Their Ligand-Mediated Delocalization in Nickel Dihalide Charge-Transfer Insulators

Occhialini,

Tseng,

Elnaggar

et al. 2024

Phys. Rev. X

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The fundamental optical excitations of correlated transition-metal compounds are typically identified with multielectronic transitions localized at the transition-metal site, such as dd transitions. In this vein, intense interest has surrounded the appearance of sharp, below-band-gap optical transitions, i.e., excitons, within the magnetic phase of correlated Ni2+ van der Waals magnets. The interplay of magnetic and charge-transfer insulating ground states in Ni2+ systems raises intriguing questions on the roles of long-range magnetic order and of metal-ligand charge transfer in the exciton nature, which inspired microscopic descriptions beyond typical dd excitations. Here we study the impact of charge transfer and magnetic order on the excitation spectrum of the nickel dihalides (NiX2, X=Cl, Br, and I) using Ni-L3 edge resonant inelastic x-ray scattering (RIXS). In all compounds, we detect sharp excitations, analogous to the recently reported excitons, and assign them to spin-singlet multiplets of octahedrally coordinated Ni2+ stabilized by intra-atomic Hund’s exchange. Additionally, we demonstrate that these excitons are dispersive using momentum-resolved RIXS. Our data evidence a ligand-mediated multiplet dispersion, which is tuned by the charge-transfer gap and independent of the presence of long-range magnetic order. This reveals the mechanisms governing nonlocal interactions of on-site dd excitations with the surrounding crystal or magnetic structure, in analogy to ground-state superexchange. These measurements thus establish the roles of magnetic order, self-doped ligand holes, and intersite-coupling mechanisms for the properties of dd excitations in charge-transfer insulators. Published by the American Physical Society 2024

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Dynamics of Frenkel Excitons in Pentacene

Cited by 4 publications

References 42 publications

Description of Shapiro steps on the potential energy surface of a Frenkel–Kontorova model, Part II: free boundaries of the chain

Description of Shapiro steps on the potential energy surface of a Frenkel–Kontorova model, Part II: free boundaries of the chain

Exciton dynamics in different aromatic hydrocarbon systems*

Nature of Excitons and Their Ligand-Mediated Delocalization in Nickel Dihalide Charge-Transfer Insulators

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