β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals

Rabaça, Sandra; Oliveira, Sandrina; Gama, V.; Santos, Isabel C.; Oliveira, G. N. P.; Lopes, Elsa B.; Canadell, Enric; Almeida, Manuel

doi:10.3390/cryst8040142

Cited by 9 publications

(24 citation statements)

References 21 publications

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“…These results indicate that the activated regime that is observed in the electrical resistivity of (CNB-EDT-TTF)4ReO4 is due to disorder localization of states near the Fermi level and not to the opening of a gap. In contrast to the electrical resistivity, the thermoelectric power, S, of all compounds shows a comparable behavior, which is identical to that previously described for the other members of this family of compounds ( Figure 4) [2,6,8]. It is well known that thermopower, as a zero current measurement, is less sensitive to defects than electrical resistivity, probing the more conducting regions of the sample, thus being less sensitive to disorder effects.…”

Section: Electronic Transport Propertiessupporting

confidence: 81%

“…The anions are found to be severely disordered; and, with tetrahedral anions either monoclinic or triclinic polymorphs have been described [7,8].…”

Section: X-ray Structurementioning

confidence: 99%

“…The compounds of this family are characterized by a unique structure of the donors assembled in paired layers (bilayer) [2]. This bilayer arrangement is promoted by an effective network of hydrogen These (CNB-EDT-TTF)4X compounds crystallize in several polymorphic phases that are associated with different donor packing patterns ("-type and -type) or anion ordering schemes [6][7][8]; for the  -type packing pattern some of these two-dimensional (2D) metals have shown superconductivity at low temperatures [6]. The most common donor packing pattern is the "-type, which occurs in salts with different anions of linear (I3 − ), tetrahedral (ClO4 − , BF4 − ), and octahedral (PF6 − ) geometry.…”

Section: Introductionmentioning

confidence: 99%

“…The most common donor packing pattern is the "-type, which occurs in salts with different anions of linear (I3 − ), tetrahedral (ClO4 − , BF4 − ), and octahedral (PF6 − ) geometry. The anions are found to be severely disordered; and, with tetrahedral anions either monoclinic or triclinic polymorphs have been described [7,8].…”

Section: Introductionmentioning

confidence: 99%

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Double Layer Conducting Salts: (CNB-EDT-TTF)4X, X = ClO4−, ReO4−, and SbF6−; Electrical Transport and Infrared Properties

et al. 2019

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Two new members of the family of bilayer compounds (CNB-EDT-TTF)4X, (CNB-EDT-TTF = 5-cyanobenzene-ethylenedithio-tetrathiafulvalene) with anions X = ReO4− and SbF6− are reported, their electron transport and optical properties investigated, and then compared to the ClO4− salt that was previously described. These compounds share the same structural type, i.e. bilayers of donors, which are packed in a β″-type pattern and then separated by layers of highly disordered anions. The absolute values of the electrical resistivity measured in single crystals within the layers were found in the range of 5 to 18 (Ωcm)−1, with a significantly sample dependence being ascribed to intrinsic disorder effects. The ClO4− and SbF6− salts exhibit metallic behavior with the resistivity decreasing upon cooling almost linearly with temperature until a broad minimum is reached between 15 and 80 K, depending on crystal quality; this is followed by an upturn of resistivity reaching values at T = 1.5 K that were comparable to those attained at room temperature. The electrical resistivity of the ReO4− salt follows a thermally activated behavior already at T = 300 K, although with a small activation energy in the range 16−18 meV. Thermoelectric power measurements yield large positive values (75–80 µV/K) at ambient temperature with a metallic behavior that is identical for all compounds. Temperature and polarization dependent infrared reflection measurements on single crystals of (CNB-EDT-TTF)4X salts, with X = ClO4−, ReO4−, and SbF6−, have been performed to obtain the optical conductivity and analyze the electronic and vibrational properties. For (CNB-EDT-TTF)4ClO4 the molecular vibrations exhibit a significant variation below T = 23 K, which suggests a charge localization phenomena.

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Section: Electronic Transport Propertiessupporting

confidence: 81%

“…The anions are found to be severely disordered; and, with tetrahedral anions either monoclinic or triclinic polymorphs have been described [7,8].…”

Section: X-ray Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Double Layer Conducting Salts: (CNB-EDT-TTF)4X, X = ClO4−, ReO4−, and SbF6−; Electrical Transport and Infrared Properties

et al. 2019

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“…The combination of a correlation-driven Mott transition and a disorder-driven Anderson transition has become more of an issue in recent years. The contribution of Rabaça et al and Prokhorova et al considers structural disorder [12][13][14]. The existence of Dirac-like electrons in α-(BEDT-TTF) 2 I 3 is another topic that has attracted interest for more than a decade, from a theoretical side [15] as well as from the side of applications [16].…”

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confidence: 99%

Advances in Organic Conductors and Superconductors

Dressel¹

2018

Crystals

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Crystalline conductors and superconductors based on organic molecules are a rapidly progressing field of solid-state science, involving chemists, and experimental and theoretical physicists from all around the world. In focus are solids with electronic properties governed by delocalized π-electrons. Although carbon-based materials of various shades have gained enormous interest in recent years, charge transfer salts are still paradigmatic in this field. Progress in molecular design is achieved via tiny but ingenious modifications, as well as by fundamentally different approaches. The wealth of exciting physical phenomena is unprecedented and could not have been imagined when the field took off almost half a century ago.Organic low-dimensional conductors are prime examples of Luttinger liquids; they exhibit a tendency toward Fermi surface instabilities, but can also be tuned across a dimensionality-driven phase diagram like no other system. Superconductivity comes at the border to ordered phases in the spin and charge sectors, and, at high fields, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is well established. The interplay between charge and magnetic order is still under debate, but electronic ferroelectricity is well established. After decades of intense research, the spin liquid state was first discovered in organic conductors when the amount of geometrical frustration and electronic correlations is just right. They drive the metal and superconductor into an insulating Mott state, solely via electron-electron interactions. However, what do we know about the effect of disorder? Can we tune the electronic properties by pressure, by light, or by field? Research is still addressing basic questions, but devices are not out of reach. These are currently open questions, as well as hot and timely topics.Although the superconducting transition temperature remains rather moderate for organic materials, the questions addressed are of fundamental importance, and for several topics molecular conductors are by far the best model system for detailed investigations. The spatial modulation of the superconducting order parameter in the Fulde-Ferrell Larkin-Ovchinikov state is certainly one of them [1,2]. The conceptional paper by Otsuka et al. reviews current ideas on the design of a spin-frustrated Mott insulator and points towards future developments in quantum spin liquids [3]. No question, this exciting research topic has placed organic crystals again at the forefront of solid-state physics. The class of β -Et x Me 4−x Z[Pd(dmit) 2 ] 2 with Z = P, As, Sb and x = 0, 1, 2 is a topic of the paper from Ueda et al. [4]. A completely new view on the structural properties of κ-(BEDT-TTF) 2 Cu 2 (CN) 3 is given by Foury-Leylekian and collaborators [5], who found that the compound contains two non-equivalent dimers in the unit cell and charge disproportionation between the dimers. Here, simple facts, assumed to be settled for decades, were revisited, such as the symmetry of a crystal; this laid new ground for the re-interpreta...

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Five-Membered Ring Systems: With O and S (Se, Te) Atoms

Aitken¹

2020

Progress in Heterocyclic Chemistry

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β”-(CNB-EDT-TTF)4BF4; Anion Disorder Effects in Bilayer Molecular Metals

Cited by 9 publications

References 21 publications

Double Layer Conducting Salts: (CNB-EDT-TTF)4X, X = ClO4−, ReO4−, and SbF6−; Electrical Transport and Infrared Properties

Double Layer Conducting Salts: (CNB-EDT-TTF)4X, X = ClO4−, ReO4−, and SbF6−; Electrical Transport and Infrared Properties

Advances in Organic Conductors and Superconductors

Five-Membered Ring Systems: With O and S (Se, Te) Atoms

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