Coherent dynamics of photoinduced phase formation in a strongly correlated organic crystal

Matsubara, Y.; Ogihara, Sho; Itatani, Jiro; Maeshima, Nobuya; Yonemitsu, Kenji; Ishikawa, Tadaharu; Okimoto, Y.; Koshihara, Shin‐ya; Hiramatsu, Takeshi; Nakano, Yoshiaki; Yamochi, Hideki; Saito, Gunzi; Onda, Ken

doi:10.1103/physrevb.89.161102

Cited by 24 publications

(18 citation statements)

References 40 publications

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“…The time-dependent Schrödinger equation for the exact many-electronquantum-phonon wave function is numerically solved by expanding the exponential evolution operator with a time slice dt=0.02 to the 15th order and by checking the conservation of the norm. 13,14 We use the leapfrog method to solve the classical equations for the lattice displacements,…”

Section: Strongly Dimerized Models With Charge-ordered Ground Statesmentioning

confidence: 99%

Negative-Temperature State Formed and Interactions Inverted by Symmetric Monocycle Optical Pulse Excitation

Yonemitsu

Nishioka

2015

J. Phys. Soc. Jpn.

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The excited state dynamics of correlated electron and electron-phonon systems triggered by an oscillating electric-field pulse of large amplitude are theoretically investigated. A "negative-temperature" state and inversion of electron-electron and electron-phonon interactions are induced even by a symmetric monocycle pulse. This fact is numerically demonstrated, using the exact diagonalization method, in a band-insulator phase of one-dimensional three-quarter-filled strongly dimerized extended Peierls-Hubbard and Holstein models. When the total-energy increment is maximized as a function of the electric field amplitude, the occupancy of the bonding and antibonding orbitals is inverted to produce a negative-temperature state. Around this state, the dependences of time-averaged electron-electron and electronphonon correlation functions on interaction parameters are opposite to those in the ground state.

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Section: Strongly Dimerized Models With Charge-ordered Ground Statesmentioning

confidence: 99%

Negative-Temperature State Formed and Interactions Inverted by Symmetric Monocycle Optical Pulse Excitation

Yonemitsu

Nishioka

2015

J. Phys. Soc. Jpn.

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“…The relationship between the Drude weight and the in-gap density of states is also discussed. Including dynamical phonons is the next move to account for realistic experimental results [75,76]. Time-dependent spectroscopies on systems with modulated hopping [42,77,78] or multi-orbitals [79,80] are also interesting open problems.…”

Section: Resultsmentioning

confidence: 99%

Time-dependent spectral properties of a photoexcited one-dimensional ionic Hubbard model: an exact diagonalization study

Okamoto

2019

New J. Phys.

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Motivated by the recent progress in time-resolved nonequilibrium spectroscopy in condensed matter, we study an optically excited one-dimensional ionic Hubbard model by exact diagonalization. The model is relevant to organic crystals, transition metal oxides, or ultracold atoms in optical lattices. We implement numerical pump-probe measurements to calculate time-dependent conductivity and single-particle spectral functions. In general, short optical excitation induces a metallic behavior imprinted as a Drude peak in conductivity or an in-gap density of states. In a Mott insulator, we find that the induced Drude peak oscillates at the pump frequency and its second harmonic. The former comes from the oscillation of currents, and the latter from the interference of single-and three-photon excited states. In a band insulator, the Drude peak oscillates only at the pump frequency, and quantities such as the double occupancy do not oscillate. The absence of the second harmonic oscillation is due to the degeneracy of multi-photon excited states. The in-gap density of states in both insulators correlates with the Drude weight and the energy absorption for weak pumping. Strong pumping leads to saturation of the in-gap density of states and to suppression of the Drude weight in the Mott regime. We have also checked that the above features are robust for insulators in the intermediate parameter range. Our study demonstrates the distinct natures of the multi-photon excited states in two different insulators.Alternatively, we can regard it as a variant of the Falicov-Kimball model [41] where f-electrons are chargeordered and frozen. Here we ignore the dynamics of the underlying objects that give the staggered modulation. This means that our results are relevant to experimental data for a short period of time before the ionic motion sets in; the model serves as a starting point for further investigation with dynamical phonons. There is also an experimental realization of the model in ultracold atoms [42].We employ an exact diagonalization method to solve the time-dependent Schrödinger equation, and implement numerical pump-probe measurements to obtain time-dependent conductivity [43-45] and singleparticle spectral functions [46,47]. Short optical pulses applied to a Mott insulator (MI) or a band insulator (BI) make the system metallic, which is indicated by a nonzero Drude peak in conductivity. We find that the Drude peak oscillates at the pump frequency in both cases, while also at the second harmonic in the MI. The second harmonic oscillation in the Mott regime is explained by a constructive interference of single-and three-photon excited states. We have confirmed that the distinct dynamic behaviors still appear for intermediate cases unless the energy gap becomes too small. The relation between the in-gap density of states and the Drude weight is also discussed.The paper is organized as follows. In section 2, an ionic Hubbard model is introduced. Section 3 is devoted to the details of the exact diagonalization method and pump...

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“…This is not the case in our study and this is an indication of the local nature of the structural trapping of the electronic excited state. This local trapping was theoretically introduced to explain the two-step dynamics [6][7][8][9], which we will discuss in the last part of this paper.…”

Section: B Response To Different Laser Fluenciesmentioning

confidence: 99%

“…It exhibits first-order insulator-to-metal (I-M) phase transition at thermal equilibrium and a gigantic ultrafast change of reflectivity under irradiation by a laser pulse in the I phase [5]. * It was shown by time-resolved optical [6,7] and vibrational spectroscopy [8] as well as ultrafast electron diffraction [9] that the photoinduced transformation proceeds stepwise. The initial electronic excited state is trapped at the molecular level within 40 fs following the electron-phonon coupled precursor state [7], while the crystal transformation is driven by slower propagation at the 100 ps time scale.…”

Section: Introductionmentioning

confidence: 99%

“…* It was shown by time-resolved optical [6,7] and vibrational spectroscopy [8] as well as ultrafast electron diffraction [9] that the photoinduced transformation proceeds stepwise. The initial electronic excited state is trapped at the molecular level within 40 fs following the electron-phonon coupled precursor state [7], while the crystal transformation is driven by slower propagation at the 100 ps time scale. Actually, different isostructural compounds of the same (EDO-TTF) 2 XF 6 family, where X stands for P, As, or Sb, have already been synthesized.…”

Section: Introductionmentioning

confidence: 99%

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Local response to light excitation in the charge-ordered phase of(EDO−TTF)2SbF6

et al. 2015

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The family of materials (EDO-TTF) 2 XF 6 represents quasi-one-dimensional quarter filled systems exhibiting insulator-to-metal (I-M) phase transition at thermal equilibrium. (EDO-TTF) 2 PF 6 is known to undergo a photoinduced I-M conversion with cooperative response to light excitation. Here we use femtosecond pump-probe experiments to study the photoresponse of (EDO-TTF) 2 SbF 6 made of a larger counteranion SbF 6 compared to the well studied (EDO-TTF) 2 PF 6 . In the early stage of the photoinduced process, we reveal a multicomponent coherent oscillating feature. The evolution of this feature with excitation density and temperature points to the local nature of the photoswitching in (EDO-TTF) 2 SbF 6 . At longer time scale, we did not detect the features associated with the transformation to the M phase, albeit observed in the PF 6 derivative. We propose a scenario whereby the bigger size of the counteranion in (EDO-TTF) 2 SbF 6 hinders the establishment of this transformation at macroscopic scale.

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Coherent dynamics of photoinduced phase formation in a strongly correlated organic crystal

Cited by 24 publications

References 40 publications

Negative-Temperature State Formed and Interactions Inverted by Symmetric Monocycle Optical Pulse Excitation

Negative-Temperature State Formed and Interactions Inverted by Symmetric Monocycle Optical Pulse Excitation

Time-dependent spectral properties of a photoexcited one-dimensional ionic Hubbard model: an exact diagonalization study

Local response to light excitation in the charge-ordered phase of(EDO−TTF)2SbF6

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