Photoinduced transition to charge-ordered phases from dynamical localization in the metallic phase of 
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Oya, Koudai; Takahashi, Atsushi

doi:10.1103/physrevb.97.115147

Cited by 5 publications

(3 citation statements)

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“…The degeneracy between the horizontal and diagonal charge-ordered states is lifted by the energy gain, and the charge distribution is mainly determined from the bond structure. [60][61][62] To maximize the energy gain,p n,m (λ) is larger for the bond with larger |β Y (λ)|. The absolute values |β Y (λ)| and therefore the energy gains for bonds b1, b1 ′ , b2, and b2 ′ , shown by thick lines in Fig.…”

Section: Resultsmentioning

confidence: 99%

Charge and dielectric response to terahertz pulses in the charge-ordered phase of α−(BEDT−TTF)2I3

2018

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We investigated the dielectric properties of the charge-ordered phase of α-(BEDT-TTF) 2 I 3 using exact numerical calculations of an extended Hubbard model. The electronic contribution to the electric polarization (electronic polarization)P of the charge-ordered ground state is obtained by directly calculating the current when transfer integrals were changed adiabatically from symmetric integrals to integrals for the charge-ordered phase without inversion symmetry. The angle of P from the positive b−axis is 36 • , which is consistent with experimental results and previous theoretical results based on density functional theory. Furthermore, we numerically calculated the dynamics induced by terahertz (THz) pulse excitation. Both the THz-pulse induced variation of the electronic polarization magnitude and that of the charge disproportionation that shows the charge-order amplitude, are largest when the electric field of the THz pulse andP have almost the same direction. This originates from the charge transfer through bond b2 ′ being dominant in both the adiabatic flow of current and THz pulse excitation. These results reproduce important features of experimental results of THz-pulse induced dynamics.Ferroelectric materials are widely used in various devices, such as random-access memory devices, capacitors, sensors, piezoelectric actuators, and optical devices. 1-3 In conventional ferroelectrics, electric polarization is governed by the rotation of polar molecules (orderdisorder type) or the displacement of ions (displacive type), and the typical time constants of polarization change vary from microseconds to milliseconds. If the ferroelectric polarization could be controlled in the picosecond time domain, ferroelectric materials could be used for advanced switching devices. Recently, ferroelectricity that arises from electron transfer, which is termed electronic ferroelectricity, 4-6 has been observed in various materials, such as multiferroics, 7-14 transition metal oxides, 15-17 and organic molecular compounds, 18-37 and much faster polarization switching is expected for the new type of ferroelectricity. 5,6 This paper focuses on α-(BEDT-TTF) 2 I 3 (BEDT-TTF: bis[ethylenedithio]tetrathiafulvalene) among various electronic ferroelectrics. The charge-transfer salts (BEDT-TTF) 2 X (X: a monovalent anion) can be described as quasi-two-dimensional strongly correlated electron systems with a quarter-filled valence band in the hole picture.As a result of the strong Coulomb interaction, α-(BEDT-TTF) 2 I 3 exhibits charge-ordering transition and a horizontal charge order forms below the transition temperature. [26][27][28][38][39][40][41][42][43][44][45][46] We show the lattice structure of α-(BEDT-TTF) 2 I 3 in Fig. 1. In the charge-ordered phase, the crystal symmetry is P 1 with no inversion symmetry, and there are crystallographically 4 nonequivalent sites and 12 nonequivalent bonds. They are labeled as indicated in Fig. 1.Sites A and B (A ′ and C) are charge rich (charge poor) in the horizontal charge-ordered state.Th...

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Section: Resultsmentioning

confidence: 99%

Charge and dielectric response to terahertz pulses in the charge-ordered phase of α−(BEDT−TTF)2I3

2018

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“…These phenomena have been observed, for instance, in materials which exhibit charge ordering [1,3,10], charge density wave [6,8], superconductivity [2,4,5,7], and excitonic condensation [9]. Simultaneously, theoretical efforts to understand their mechanisms as well as to pursue a way of controlling electronic phases have been made recently, where roles of electron-electron (e-e) and/or electron-phonon (e-ph) interactions on laser-induced dynamics have been intensively studied [11][12][13][14][15][16][17][18][19][20][21][22]. For excitonic insulators (EIs), a transient gap enhancement by photoexcitation has been observed in a candidate material Ta 2 NiSe 5 [9].…”

Section: Introductionmentioning

confidence: 99%

Photoinduced dynamics of excitonic order and Rabi oscillation in the two-orbital Hubbard model

Tanaka,

Yonemitsu

2020

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We investigate the condition for the photoinduced enhancement of an excitonic order in a twoorbital Hubbard model, which has been theoretically proposed in our previous work [Phys. Rev. B 97, 115105 (2018)], and analyze it from the viewpoint of the Rabi oscillation. Within the mean-field approximation, we simulate real-time dynamics of an excitonic insulator with a direct gap, where the pair condensation in the initial state is of BEC nature and the photoexcitation is introduced by electric dipole transitions. We first discuss that in the atomic limit our model is reduced to a twolevel system that undergoes the Rabi oscillation, so that for single cycle pulses physical quantities after the photoirradiation are essentially determined by the ratio of the Rabi frequency to the pump-light frequency. Then, it is shown that this picture holds even in the case of nonzero transfer integrals where each one-particle state exhibits the Rabi oscillation leading to the enhancement of the excitonic order. We demonstrate that effects of electron-phonon interactions do not alter the results qualitatively. We also examine many-body dynamics by the exact diagonalization method on small clusters, which strongly suggests that our mechanism for the enhancement of the exctionic order survives even when quantum fluctuations are taken into account.

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“…There has been a rapid development of correlated systems far from equilibrium that are driven by strong alternating current electric fields. [68][69][70][71][72][73][74] THz-pulse-induced phase transitions are a key example of this interesting phenomena.…”

Section: Introductionmentioning

confidence: 99%

Terahertz pulse induced transitions between ionic and neutral phases and electronic polarization reversal in TTF-CA

2019

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We have investigated the terahertz (THz)-pulse induced dynamics of tetrathiafulvalene-pchloranil near the boundary between the ionic and neutral phases with the use of exact numerical calculations of an extended Hubbard model coupled with lattice motion. For the ionic phase, when the applied electric field of the THz-pulse opposes the electronic contribution to the electric polarization (electronic polarization)P el of the ground state and the maximum amplitude of electric field is greater than a threshold value, the THz-pulse excited state changes as I A → N → I B → N → I A → N → • • • (I A ground state case) or I B → N → I A → N → I B → N → • • • (I B ground state case), where N shows the neutral state, I A (I B) shows the ionic state withP el < 0 (P el > 0), and the phase of the bond length alternation of I A is opposite to that of I B. For the neutral phase, when the maximum amplitude of the electric field is greater than a threshold value, the THz-pulse excited state changes as N → I B → N → I A → N → I B → • • • (positive electric field case) or N → I A → N → I B → N → I A → • • • (negative electric field case). The phase transitions and electronic polarization reversal are driven by time variation of the lattice order parameter, which indicates the magnitude and phase of the bond length alternation, and the lattice motion is induced by THz-pulse excitation through the electron-lattice coupling. Transitions between the ionic and neutral phases occur and electronic polarization reverses on a picosecond time scale together with the realizable magnitude of the THz pulse both in the ionic and neutral phases near the phase boundary.

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Photoinduced transition to charge-ordered phases from dynamical localization in the metallic phase of α−(BEDT-TTF)2I3

Cited by 5 publications

References 55 publications

Charge and dielectric response to terahertz pulses in the charge-ordered phase of α−(BEDT−TTF)2I3

Charge and dielectric response to terahertz pulses in the charge-ordered phase of α−(BEDT−TTF)2I3

Photoinduced dynamics of excitonic order and Rabi oscillation in the two-orbital Hubbard model

Terahertz pulse induced transitions between ionic and neutral phases and electronic polarization reversal in TTF-CA

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