Collective Excitation of an Electric Dipole on a Molecular Dimer in an Organic Dimer-Mott Insulator

Itoh, K.; Itoh, Hirotake; Naka, Masaaki; Saito, Shingo; Hosako, Iwao; Yoneyama, N.; Ishihara, Sumio; Sasaki, T.; Iwai, Shinichiro

doi:10.1103/physrevlett.110.106401

Cited by 63 publications

(77 citation statements)

References 28 publications

(39 reference statements)

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“…22 A broad band was observed in the optical conductivity around 1 THz which grows below 60 K; it was attributed to the collective excitation of the fluctuating intradimer electric dipole. 23 In the same temperature range the spin susceptibility decreases gradually and (T 1 T ) −1 obtained from 13 C-NMR measurements increases, both indicating the development of AFM correlations. Eventually the susceptibility drops sharply below 10 K where (…”

Section: 14mentioning

confidence: 93%

“…21 The latter data discard the original interpretation by Abdel-Jawad and Hotta 20,26 based on the collective excitation of the intradimer electric dipole; this idea was previously also used to explain the microwave and terahertz anomalous charge behavior. 22,23 Nevertheless, the vibrational data allow for the presence of fast temporal fluctuations of charge distribution with the exchange frequency of 10 11 Hz, whose softening is predicted theoretically. 27 While fluctuating intradimer electric dipoles have been still discussed in literature as the possible source of terahertz response 64 , it is definitely clear that they cannot be invoked to explain dielectric response at low frequencies.…”

Section: B Dielectric Responsementioning

confidence: 99%

“…Since these arrangements are not independent, local order may develop over a length scale of a few unit cells. Interestingly, the unusually broad and strong feature observed in the optical spectra at around 1 THz [23,65] only shows up for the electric field polarized along the direction of the disordered CN groups (E c). This infers a coupling to the fluctuating charge which increases as the temperature is lowered down to low temperatures where it actually starts to decrease.…”

Section: )]mentioning

confidence: 99%

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Anisotropic charge dynamics in the quantum spin-liquid candidateκ−(BEDT-TTF)2Cu2(CN)3

et al. 2014

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We have in detail characterized the anisotropic charge response of the dimer Mott insulator κ-(BEDT-TTF)2Cu2(CN)3 by dc conductivity, Hall effect and dielectric spectroscopy. At room temperature the Hall coefficient is positive and close to the value expected from stoichiometry; the temperature behavior follows the dc resistivity ρ(T ). Within the planes the dc conductivity is well described by variable-range hopping in two dimensions; this model, however, fails for the out-ofplane direction. An unusually broad in-plane dielectric relaxation is detected below about 60 K; it slows down much faster than the dc conductivity following an Arrhenius law. At around 17 K we can identify a pronounced dielectric anomaly concomitantly with anomalous features in the mean relaxation time and spectral broadening. The out-of-plane relaxation, on the other hand, shows a much weaker dielectric anomaly; it closely follows the temperature behavior of the respective dc resistivity. At lower temperatures, the dielectric constant becomes smaller both within and perpendicular to the planes; also the relaxation levels off. The observed behavior bears features of relaxor-like ferroelectricity. Because heterogeneities impede its long-range development, only a weak tunneling-like dynamics persists at low temperatures. We suggest that the random potential and domain structure gradually emerge due to the coupling to the anion network.

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Section: 14mentioning

confidence: 93%

Section: B Dielectric Responsementioning

confidence: 99%

Section: )]mentioning

confidence: 99%

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Anisotropic charge dynamics in the quantum spin-liquid candidateκ−(BEDT-TTF)2Cu2(CN)3

et al. 2014

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“…In this paper, we show that the onsite Coulomb integral can be modulated in molecular solids by driving local molecular degrees of freedom to large amplitudes [10,11]. The excitation of local modes at mid-infrared frequencies is different from the case of nonlinear phononics in that the molecular orbital and concomitantly the onsite charge density are controlled [12,13], with each site maintained in its electronic ground state.…”

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confidence: 99%

THz-Frequency Modulation of the HubbardUin an Organic Mott Insulator

et al. 2015

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Abstract:We use midinfrared pulses with stable carrier-envelope phase offset to drive molecular vibrations in the charge transfer salt ET-F2TCNQ, a prototypical one-dimensional Mott insulator. We find that the Mott gap, which is probed resonantly with 10 fs laser pulses, oscillates with the pump field. This observation reveals that molecular excitations can coherently perturb the electronic on-site interactions (Hubbard U) by changing the local orbital wave function. The gap oscillates at twice the frequency of the vibrational mode, indicating that the molecular distortions couple quadratically to the local charge density.

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“…[5][6][7] However, no consensus has been reached yet on the origin of the ferroelectric signatures detected in the strongly dimerized κ-(BEDT-TTF) 2 X salts. [8][9][10][11][12] In these compounds, the BEDT-TTF dimers are arranged in a triangular lattice with a relatively high geometrical frustration. In some of them, indications of charge-ordering phenomena have been reported, but in-depth studies are missing 13,14 .…”

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confidence: 99%

Anion effects on electronic structure and electrodynamic properties of the Mott insulatorκ−(BEDT−TTF)2Ag2(CN)3
Pinterić
¹
,
Lazić
²
,
Pustogow
³

et al. 2016
Phys. Rev. B
41
4
86
0
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The Mott insulator κ-(BEDT-TTF)2Ag2(CN)3 forms a highly-frustrated triangular lattice of S = 1/2 dimers with a possible quantum-spin-liquid state. Our experimental and numerical studies reveal the emergence of a slight charge imbalance between crystallographically inequivalent sites, relaxor dielectric response and hopping dc transport. In a broader perspective we conclude that the universal properties of strongly-correlated charge-transfer salts with spin liquid state are an anion-supported valence band and cyanide-induced quasi-degenerate electronic configurations in the relaxed state. The generic low-energy excitations are caused by charged domain walls rather than by fluctuating electric dipoles. They give rise to glassy dynamics characteristic of dimerized Mott insulators, including the sibling compound κ-(BEDT-TTF)2Cu2(CN)3.PACS numbers: 75.10. Kt, 77.22.Gm, Electronic ferroelectricity and multiferroicity attracts great attention of condensed matter physicists due to their fundamental and technological importance. 1-3 They are identified in systems with strong electronic correlations such as transition-metal oxides and low-dimensional charge-transfer molecular solids. In the latter category, electric polarization arises from valence instability and charge ordering. In both cases, breaking the inversionsymmetry results in the concurrence of non-equivalent charge-sites and bonds. 4 There is no doubt that electron correlations are fundamental for stabilizing the ferroelectric ground state, nevertheless, experimental evidence indicates that the delicate interplay of Coulomb forces and structural changes within the coupled molecular-anion system have to be taken into account. Along these lines a solid understanding of electronic ferroelectricity was achieved for the families of quasi-one-dimensional organic charge-transfer salts: (TMTTF) 2 X and TTF-X, but also some layered (BEDT-TTF) 2 X systems. [5][6][7] However, no consensus has been reached yet on the origin of the ferroelectric signatures detected in the strongly dimerized κ-(BEDT-TTF) 2 X salts. [8][9][10][11][12] In these compounds, the BEDT-TTF dimers are arranged in a triangular lattice with a relatively high geometrical frustration. In some of them, indications of charge-ordering phenomena have been reported, but in-depth studies are missing 13,14 . On the other hand, the Mott dimer insulators κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl and κ-(BEDT-TTF) 2 Cu 2 (CN) 3 , called κ-CuCN, have been thoroughly studied because they are discussed as prototypes of a molecular multiferroic and quantum spin liquid (QSL) systems. 9,15 It turns out to be extremely challenging to reconcile the idea of quantum electric dipoles on molecular dimers interacting via dipolar-spin coupling [16][17][18][19] with the experimentally evidenced absence of any considerable charge imbalance. So far no global structural changes and no charge disproportionation between molecular dimer sites larger than 2δ ρ ≈ ±0.01e that could break the symmetry have been found. 20,21 In the case of the QSL κ-...

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Collective Excitation of an Electric Dipole on a Molecular Dimer in an Organic Dimer-Mott Insulator

Cited by 63 publications

References 28 publications

Anisotropic charge dynamics in the quantum spin-liquid candidateκ−(BEDT-TTF)2Cu2(CN)3

Anisotropic charge dynamics in the quantum spin-liquid candidateκ−(BEDT-TTF)2Cu2(CN)3

THz-Frequency Modulation of the HubbardUin an Organic Mott Insulator

Anion effects on electronic structure and electrodynamic properties of the Mott insulatorκ−(BEDT−TTF)2Ag2(CN)3
Pinterić
¹
,
Lazić
²
,
Pustogow
³

et al. 2016
Phys. Rev. B
41
4
86
0
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Collective Excitation of an Electric Dipole on a Molecular Dimer in an Organic Dimer-Mott Insulator

Cited by 63 publications

References 28 publications

Anisotropic charge dynamics in the quantum spin-liquid candidateκ−(BEDT-TTF)2Cu2(CN)3

Anisotropic charge dynamics in the quantum spin-liquid candidateκ−(BEDT-TTF)2Cu2(CN)3

THz-Frequency Modulation of the HubbardUin an Organic Mott Insulator

Anion effects on electronic structure and electrodynamic properties of the Mott insulatorκ−(BEDT−TTF)2Ag2(CN)3Pinterić1, Lazić2, Pustogow3 et al. 2016Phys. Rev. B414860View full textAdd to dashboardCite

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Anion effects on electronic structure and electrodynamic properties of the Mott insulatorκ−(BEDT−TTF)2Ag2(CN)3
Pinterić
¹
,
Lazić
²
,
Pustogow
³

et al. 2016
Phys. Rev. B
41
4
86
0
View full text Add to dashboard Cite