Terahertz-Field-Induced Large Macroscopic Polarization and Domain-Wall Dynamics in an Organic Molecular Dielectric

Morimoto, Takeshi; Miyamoto, T.; Yamakawa, Hisashi; Terashige, T.; Ono, Tetsu; Kida, N.; Okamoto, Hiroshi

doi:10.1103/physrevlett.118.107602

Cited by 35 publications

(35 citation statements)

References 40 publications

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“…In the I phase of TTF-CA, second-harmonic generation (SHG) was observed [16,41,42]. This suggests that ferroelectric polarization is indeed formed on a macroscopic scale.…”

Section: Imaging Of Ferroelectric Domainsmentioning

confidence: 81%

“…Electronic-type dielectrics will be good target materials to pursue such a control of polarization for the achievement of ultrafast optical switching. In this section, we review the recent study, which aimed at the ultrafast generation of large polarization by a terahertz electric field in the N phase of TTF-CA [42].…”

Section: Rapid Generation Of Large Polarizationmentioning

confidence: 99%

“…In this paper, we review our studies of the photoinduced transitions from the N phase to the I phase (the NI transition) and from the I phase to the N phase (IN transition) in TTF-CA based upon femtosecond-pump-probe spectroscopy. In addition, as a new topic in the field of PIPTs, we report our recent study using a strong terahertz-electric-field pulse, that is, the modulation and generation of ferroelectric polarization by a strong terahertz-electric-field pulse in TTF-CA [41,42].…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast Electron and Molecular Dynamics in Photoinduced and Electric-Field-Induced Neutral–Ionic Transitions

2017

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Mixed-stacked organic molecular compounds near the neutral-ionic phase boundary, represented by tetrathiafulvalene-p-chloranil (TTF-CA), show a unique phase transition from a paraelectric neutral (N) phase to a ferroelectric ionic (I) phase when subjected to decreasing temperature or applied pressure, which is called an NI transition. This NI transition can also be induced by photoirradiation, in which case it is known as a prototypical 'photoinduced phase transition'. In this paper, we focus on the ultrafast electron and molecular dynamics in the transition between the N and I states induced by irradiation by a femtosecond laser pulse and a terahertz electric-field pulse in TTF-CA. In the first half of the paper, we review the photoinduced N-to-I transition in TTF-CA studied by femtosecond-pump-probe reflection spectroscopy. We show that in the early stage of the transition, collective charge transfers occur within 20 fs after the photoirradiation, and microscopic one-dimensional (1D) I domains are produced. These ultrafast I-domain formations are followed by molecular deformations and displacements, which play important roles in the stabilization of photogenerated I domains. In the photoinduced I-to-N transition, microscopic 1D N domains are also produced and stabilized by molecular deformations and displacements. However, the time characteristics of the photoinduced N-to-I and I-to-N transitions in the picosecond time domain are considerably different from each other. In the second half of this paper, we review two phenomena induced by a strong terahertz electric-field pulse in TTF-CA: the modulation of a ferroelectric polarization in the I phase and the generation of a large macroscopic polarization in the N phase.

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“…In the I phase of TTF-CA, second-harmonic generation (SHG) was observed [16,41,42]. This suggests that ferroelectric polarization is indeed formed on a macroscopic scale.…”

Section: Imaging Of Ferroelectric Domainsmentioning

confidence: 81%

Section: Rapid Generation Of Large Polarizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultrafast Electron and Molecular Dynamics in Photoinduced and Electric-Field-Induced Neutral–Ionic Transitions

2017

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“…The thermal excitation of these 1D I nanodomains may become significant when approaching the N-I transition, where the energies of N and I states, or more precisely their chemical potential, becomes close, and so their excitation energy is governed by the domain-wall energy E DW . In addition, the activation of a weak a g band, observed in infra-red spectrum of the N phase of TTF-CA [90] and the similar TTF-QBrCl 3 [56], has been interpreted as resulting from the local loss of inversion symmetry in dimerized nanodomains. The concentration of dimerized I species in TTF-CA is estimated to about twenty percent on approaching T NI [87].…”

Section: One-dimensional Correlated Fluctuationsmentioning

confidence: 99%

“…The most surprising feature remains that the generated lattice mode keeps the same frequency in each state and is temperature-independent, even if this dynamic picture takes place on the potential energy surface of the electronically excited state. Moreover, some new features have been recently reported with the response of the ground state of the N phase to a strong THz electric-field pulse [90]. Large induced macroscopic polarization is observed thanks to a second harmonic generation probe, with an oscillatory part.…”

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confidence: 98%

Back to the Structural and Dynamical Properties of Neutral-Ionic Phase Transitions

et al. 2017

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Abstract:Although the Neutral-Ionic transition in mixed stack charge-transfer crystals was discovered almost forty years ago, many features of this intriguing phase transition, as well as open questions, remain at the heart of today's science. First of all, there is the most spectacular manifestation of electronic ferroelectricity, in connection with a high degree of covalency between alternating donor and acceptor molecules along stacks. In addition, a charge-transfer instability from a quasi-neutral to a quasi-ionic state takes place concomitantly with the stack dimerization, which breaks the inversion symmetry. Moreover, these systems exhibit exceptional one-dimensional fluctuations, with an enhancement of the effects of electron-lattice interaction. This may lead to original physical pictures for the dynamics of pre-transitional phenomena, as the possibility of a pronounced Peierls-type instability and/or the generation of unconventional non-linear excitations along stacks. Last but not least, these mixed stack charge-transfer systems constitute a valuable test bed to explore some of the key questions of ultrafast photo-induced phenomena, such as multiscale dynamics, selective coherent excitations and non-linear responsiveness. These different aspects will be discussed through the structural and dynamical features of the neutral-ionic transition, considering old and recent results, open questions and future opportunities. In particular, we revisit the structural changes and symmetry considerations, the pressure-temperature phase diagrams and conclude by their interplay with the photo-induced dynamics.

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Dynamic Terahertz Plasmonics Enabled by Phase‐Change Materials

Jeong

Bahk

Kim

2019

Advanced Optical Materials

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Phase‐change phenomena have been an attractive research theme for decades due to the dynamic transition of material properties providing extraordinary capabilities for versatile optical device applications. Even at the terahertz (THz) frequency regime, phase‐change materials (PCMs) promote the development of dynamic devices, especially when combined with a plasmonic approach delivering strong field enhancement and localization. According to the design of plasmonic metamaterials or hybrid composites, PCMs can actively modulate the electromagnetic properties of THz waves through thermal, electrical, and optical means. In turn, THz waves can affect the PCM properties in the nonlinear regime due to the intense field strength enhancement by plasmonic structures. Here, a few types of PCMs demonstrating promising potential in THz plasmonic applications are introduced. Starting from the best‐known transition metal oxide, vanadium dioxide (VO2), which possesses an insulator‐to‐metal phase transition near room temperature, superconductors, chalcogenides, ferroelectrics, liquid crystals, and liquid metals are covered along with their phase‐change properties and the control mechanisms infused with THz plasmonic applications. The corresponding recent progress presenting how PCMs combined with plasmonic structures can demonstrate effective THz modulation is reviewed. This general overview may provide a better understanding of dynamic THz plasmonics and new ideas for future THz technology.

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Terahertz-Field-Induced Large Macroscopic Polarization and Domain-Wall Dynamics in an Organic Molecular Dielectric

Cited by 35 publications

References 40 publications

Ultrafast Electron and Molecular Dynamics in Photoinduced and Electric-Field-Induced Neutral–Ionic Transitions

Ultrafast Electron and Molecular Dynamics in Photoinduced and Electric-Field-Induced Neutral–Ionic Transitions

Back to the Structural and Dynamical Properties of Neutral-Ionic Phase Transitions

Dynamic Terahertz Plasmonics Enabled by Phase‐Change Materials

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