Two different ground states in K-intercalated polyacenes

Phan, Quynh; Heguri, Satoshi; Tamura, Hiroyuki; Nakano, T.; Nozue, Yasuo; Tanigaki, Katsumi

doi:10.1103/physrevb.93.075130

Cited by 23 publications

(41 citation statements)

References 34 publications

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“…[10,11,14] could be understood in this context. On the other hand, additional experimental results point to a prompt metal-insulator transition at the first stages of doping [15][16][17]. A precise description of pentacene compounds with less than one potassium atom per unit cell could be theoretically done using crystal supercells of pentacene crystal.…”

Section: A Kpentacene Compoundmentioning

confidence: 99%

“…[17]. To this end we start forming an isolated K 2 Pentacene 2 dimer that is later used as the unit of a herringbone structure [34].…”

Section: A Kpentacene Compoundmentioning

confidence: 99%

“…Two papers published in 2016 present two quite contradictory scenarios. Phan et al [17] report on thin films with the 1:1 stoichiometry. Napthalene, anthracene, tetracene, and pentacene are potassium intercalated and all of them show insulating character although the underlying mechanisms are different for short versus long PAHs.…”

Section: Introductionmentioning

confidence: 99%

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Structural and electronic changes of pentacene induced by potassium doping

Guijarro

Vergés

2017

Phys. Rev. B

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Potassium is introduced into the crystalline herringbone structure of pentacene searching for a compound showing metallic electronic transport properties and, hopefully, superconductivity at small enough temperatures. Several possible structures for stoichiometric KPentacene (1:1), K 2 Pentacene (2:1), and K 3 Pentacene (3:1) compounds are theoretically investigated. Detailed densities of states for all of them are presented. As a more prominent result, a new monoclinic structure has been stabilized for the potassium richer material that could correspond to the recently synthesized superconducting phase of K 3 Pentacene. Although energetically unfavorable, it is the only metallic candidate found to date.

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Section: A Kpentacene Compoundmentioning

confidence: 99%

“…[17]. To this end we start forming an isolated K 2 Pentacene 2 dimer that is later used as the unit of a herringbone structure [34].…”

Section: A Kpentacene Compoundmentioning

confidence: 99%

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Structural and electronic changes of pentacene induced by potassium doping

Guijarro

Vergés

2017

Phys. Rev. B

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“…As neither compound is metallic, these small magnetisation values indicate the formation of a singlet ground state: this is consistent for K2Pentacene with filling of the LUMO-derived band because of the separation of over 1 eV between LUMO and LUMO+1 in bulk pentacene 37 , consistent with the conclusions of recent magnetic and spectroscopic studies of K intercalated polyacenes. 19 Density functional theory (DFT) calculations show that the first unoccupied electronic band of solid pristine picene is derived from both the LUMO and LUMO+1 orbitals of the two picene molecules in the cell. 35,38 In a rigid band treatment, charging the two picene molecules to dianions would place four electrons into this band, leaving it half filled (Supplementary Figure 25) 38 , suggesting that K2Picene should be metallic.…”

Section: Structure Of K2picenementioning

confidence: 99%

“…This contrasts with C60, where the octahedral and tetrahedral voids in the fcc lattice are adjacent to the conjugated π-electron system (Figure 1b Pentacene is the linear isomer of picene, and also adopts the herringbone structure, 16 with ω = 52.9° (Supplementary Figure 1). Bulk KxPentacene (x = 1, 2 and 3.6) has previously been reported without structural characterisation, [17][18][19] and metallic conductivity has been reported in potassium-doped pentacene thin films. [20][21][22][23][24] As pentacene is more readily available than picene, we chose initially to address the synthesis of potassium-intercalated pentacene samples suitable for structural analysis, before applying these protocols to the picene system.…”

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confidence: 99%

Redox-controlled potassium intercalation into two polyaromatic hydrocarbon solids

et al. 2017

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Alkali metal intercalation into polyaromatic hydrocarbons (PAHs) has been studied intensely following reports of superconductivity in a number of potassium-and rubidium-intercalated materials. There are however no reported crystal structures to inform understanding of the chemistry and physics because of the complex reactivity of PAHs with strong reducing agents at high temperature. Here we present the synthesis of crystalline K2Pentacene and K2Picene by a solid-solid insertion protocol that uses potassium hydride as a redox-controlled reducing agent to access the PAH dianions, enabling determination of their crystal structures. In both cases, the inserted cations expand the parent herringbone packings by reorienting the molecular anions to create multiple potassium sites within initially dense molecular layers, and thus interact with the PAH anion π-systems. The synthetic and crystal chemistry of alkali metal intercalation into PAHs differs from that into fullerenes and graphite, where the cation sites are pre-defined by the host structure.Reaction of alkali and alkaline earth metals with carbon-based molecular solids has been extensively studied in the search for novel magnetic and electronic properties, with a particular focus on superconductivity. [1][2][3][4][5][6] For example, alkali metal intercalation into solid C60 produces A3C60 superconductors, with Tc as high as 38 K for Cs3C60 at 7 kbar. 6 In these materials, cations occupy the interstitial voids that already exist in the host e.g., in the fcc lattice of C60 (Figure 1). 7 Reaction of potassium with picene (C22H14), a phenacene composed of five fused benzene rings, has been reported to afford superconductivity at 18 K. 8 Superconductivity in other alkali-metal polyaromatic hydrocarbons (PAHs) was subsequently reported in phenanthrene-, dibenzopentacene-and coronene-based materials, with the highest reported Tc of 33 K claimed 2 in potassium-doped 1,2:8,9-dibenzopentacene. [9][10][11] Despite the significant interest in these materials, to date no crystal structure has been determined for any of the alkali-metal PAH systems. This structural information is a prerequisite for materials design and for understanding of both physical properties and reaction chemistry.Picene, like many other PAHs (including molecules such as phenanthrene 12 which is reported to afford superconductivity on cation insertion), crystallises in the herringbone structure, 13 with layers consisting of two parallel one-dimensional chains of molecules with opposing inclinations defined by an intermolecular angle, ω, of 57.89(7)° (Supplementary Figure 1). 14 The largest voids in the structure are located between the picene layers, adjacent to the saturated C-H bonds and far from the electron density of the PAH π-systems ( Figure 1a). This contrasts with C60, where the octahedral and tetrahedral voids in the fcc lattice are adjacent to the conjugated π-electron system (Figure 1b Pentacene is the linear isomer of picene, and also adopts the herringbone structure, 16 with ω = 52...

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Theory of zero‐phonon decay luminescence of semiconductor excitons

Koch

Semkat

Stolz

et al. 2016

Fortschritte der Physik

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We present a theoretical approach to the zero‐phonon decay luminescence of excitons. In a two‐step approach, the weakly interacting condensed exciton gas is Bogolyubov transformed before the resulting quasiparticles are coupled to the photon field. The field–field correlation function, which gives the luminescence intensity and first‐order coherence, is calculated in the framework of real‐time Green's functions of the photons. The resulting spectrum of the new, so‐called bogolariton, quasiparticles is discussed.

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Two different ground states in K-intercalated polyacenes

Cited by 23 publications

References 34 publications

Structural and electronic changes of pentacene induced by potassium doping

Structural and electronic changes of pentacene induced by potassium doping

Redox-controlled potassium intercalation into two polyaromatic hydrocarbon solids

Theory of zero‐phonon decay luminescence of semiconductor excitons

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