Essential role of anions in the charge ordering transition of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-(BEDT-TTF)<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>I<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>

Alemany, Pere; Pouget, Jean‐Paul; Canadell, Enric

doi:10.1103/physrevb.85.195118

Cited by 91 publications

(173 citation statements)

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“…It is interesting to note that this behavior is in strong contrast to the behavior of the TMTTF-salts [48] where the transition of the charge ordered state evolves continuously indicated by the charge imbalance. In this way, it resembles the behavior observed at the charge-order phase transition of α-(BEDT-TTF) 2 I 3 where a strong involvement of the lattice was shown recently [61][62][63][64]. Moreover, several features reveal a positive shift instead of a negative one.…”

Section: B-directionmentioning

confidence: 51%

Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics

Dressel

Peterseim

2017

Crystals

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Abstract:The neutral-ionic phase transition in TTF-CA was investigated by steady-state and time-resolved infrared spectroscopy. We describe the growth of high-quality single crystals and their characterization. Extended theoretical calculations were performed in order to obtain the band structure, the molecular vibrational modes and the optical spectra along all crystallographic axes. The theoretical results are compared to polarization-dependent infrared reflection experiments. The temperature-dependent optical conductivity is discussed in detail. We study the photo-induced phase transition in the vicinity of thermally-induced neutral-ionic transition. The observed temporal dynamics of the photo-induced states is attributed to the random-walk of neutral-ionic domain walls. We simulate the random-walk annihilation process of domain walls on a one-dimensional chain.

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Section: B-directionmentioning

confidence: 51%

Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics

Dressel

Peterseim

2017

Crystals

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“…Ishibashi et al, made Mulliken charge analyses in their ab initio calculation of the band structure of α-I 3 [158]. Recently, the site hole numbers were reported by Alemany using the DFT approach considering only the valence electrons [129]. In Table 3, their results are compared with the experimental results.…”

Section: Site Charge Distribution In Metallic Phase At Ambient Pressurementioning

confidence: 84%

“…Decisive evidence for the breaking of inversion symmetry was given by the experiment of second harmonic generation (SHG) [124]. Recently, Alemany et al, pointed out that the hydrogen bond between the ethylene groups of BEDT-TTF and I 3 − plays an essential role in the CO transition of α-I 3 [129]. In the MI transition of α-I 3 , Raman [111] and infrared [130] spectra showed drastic changes as seen in Figure 18.…”

Section: α-(Bedt-ttf) 2 I 3 and Related Compoundsmentioning

confidence: 99%

“…Kakiuchi et al, examined the breakdown of Friedel's law by anomalous scattering effect, and they concluded a symmetry reduction from 1 P to P1 [128]. Using the space group P1, they determined the molecular geometry of each site, and provided consistent result for the site charge distribution as ρ A = 0.82 (9), ρ B = 0.73 (9), ρ A' = 0.29 (9), ρ C = 0.26(9) at 20 K. Recently, Alemany et al, reported the site charges as ρ A = 0.638, ρ B = 0.577, ρ A′ = 0.438, ρ C = 0.359 using a numerical atomic orbital density functional theory (DFT) approach [129]. This CO amplitude ρ max = 0.28 is significantly smaller than the experimentally estimated value of ρ max = 0.56-0.70.…”

Section: α-(Bedt-ttf) 2 I 3 and Related Compoundsmentioning

confidence: 99%

“…This result suggests that the crystal structure of the zero-gap state of α-I 3 is slightly modulated so as to equalize sites B and C. However, there still remains a site-charge difference in ZGS. Alemany et al, reported the band calculation of α-I 3 [129] using the atomic parameters at 1.76 GPa that is determined by Kondo et al [163]. They used the generalized gradient approximation to DFT, and found the contact point at the Fermi level.…”

Section: Site Charge Distribution In Metallic Phase At Ambient Pressurementioning

confidence: 99%

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Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Yakushi

2012

Crystals

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This paper reviews charge ordering in the organic conductors, β″-(BEDT-TTF) (TCNQ), θ-(BEDT-TTF) 2 X, and α-(BEDT-TTF) 2 X. Here, BEDT-TTF and TCNQ represent bis(ethylenedithio)tetrathiafulvalene and 7,7,8,8-tetracyanoquinodimethane, respectively. These compounds, all of which have a quarter-filled band, were evaluated using infrared and Raman spectroscopy in addition to optical conductivity measurements. It was found that β″-(BEDT-TTF)(TCNQ) changes continuously from a uniform metal to a chargeordered metal with increasing temperature. Although charge disproportionation was clearly observed, long-range charge order is not realized. Among six θ-type salts, four compounds with a narrow band show the metal-insulator transition. However, they maintain a large amplitude of charge order (Δρ~0.6) in both metallic and insulating phases. In the X = CsZn(SCN) 4 salt with intermediate bandwidth, the amplitude of charge order is very small (Δρ < 0.07) over the whole temperature range. However, fluctuation of charge order is indicated in the Raman spectrum and optical conductivity. No indication of the fluctuation of charge order is found in the wide band X = I 3 salt. In α-(BEDT-TTF) 2 I 3 the amplitude of charge order changes discontinuously from small amplitude at high temperature to large amplitude (Δρ max~0 .6) at low temperature. The long-range chargeordered state shows ferroelectric polarization with fast optical response. The fluctuation of multiple stripes occurs in the high-temperature metallic phase. Among α-(BEDT-TTF) 2 MHg(SCN) 4 (X = NH 4 , K, Rb, Tl), the fluctuation of charge order is indicated only in the X = NH 4 salt. α′-(BEDT-TTF) 2 IBr 2 shows successive phase transitions to the ferroelectric state keeping a large amplitude of charge order (Δρ max~0 .8) over the whole temperature range. It was found that the amplitude and fluctuation of charge order in these compounds is enhanced as the kinetic energy (bandwidth) decreases. OPEN ACCESSCrystals 2012, 2 1292

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Theoretical Model and Progress of Organic Thermoelectric Materials

Zhang¹,

Zhu²

2022

Organic Thermoelectrics

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Essential role of anions in the charge ordering transition ofα-(BEDT-TTF)2I3

Cited by 91 publications

References 50 publications

Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics

Infrared Investigations of the Neutral-Ionic Phase Transition in TTF-CA and Its Dynamics

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Theoretical Model and Progress of Organic Thermoelectric Materials

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