Molecular Dynamics at Electrical- and Optical-Driven Phase Transitions: Time-Resolved Infrared Studies Using Fourier-Transform Spectrometers

Peterseim, Tobias; Dressel, Martin

doi:10.1007/s10762-016-0294-5

Cited by 5 publications

(3 citation statements)

References 77 publications

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“…In most cases, the charge-transfer band [5] with its maximum located at 0.65 eV was excited in these experiments while the probing range was predominant in the visible spectral range [76,81]. There are only very few investigations dedicated to the infrared spectral range [82][83][84].…”

Section: Photo-induced Phase Transition In Ttf-camentioning

confidence: 93%

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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: Photo-induced Phase Transition In Ttf-camentioning

confidence: 93%

“…The time-dependent response of the infrared reflectivity signal is detected by a Bruker Vertex 80v Fourier-transform spectrometer operating in the step-scan mode as described in detail in Refs. [83,84]. A sketch of the experimental setup is given in Figure 23.…”

Section: Experimental Configurationmentioning

confidence: 99%

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

Dressel

Peterseim

2017

Crystals

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“…It will be crucial also to perform experiments which span a large range in spatial and temporal scales in order to investigate the intrinsic multi-scale nature of the complete transformation path, from the molecular to material scale, and from coherent dynamics, from the generation of optical phonons and propagative strain wave, to thermal stochastic phenomena, such as electron-lattice and phonon-phonon energy dissipation, heat diffusion, and so on [145]. The investigation of the kinetics to recover thermal equilibrium state, after a strong light-induced perturbation, may also provide some information on the dynamical transformation mechanism, in relation with the domain-wall dynamics [146,147]. Ultrafast high field physics is really a new adventure for the physics of correlated systems, and this is the beginning for NI systems, as for instance the observation of the modulation of ferroelectric polarization in TTF-CA [148,149] or the use of very intense electric field in ultra-short mid-infrared pulse [150].…”

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confidence: 99%

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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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Electrically induced phase transition inα−(BEDT-TTF)2I3: Indications for Dirac-like hot charge carriers

et al. 2016

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The two-dimensional organic conductor α-(BEDT-TTF)2I3 undergoes a metal-insulator transition at TCO = 135 K due to electronic charge ordering. We have conducted time-resolved investigations of its electronic properties in order to explore the field-and temperature-dependent dynamics. At a certain threshold field, the system switches from low-conducting to a high-conducting state, accompanied by a negative differential resistance. Our time-dependent infrared investigations indicate that close to TCO the strong electric field pushes the crystal into a metallic state with optical properties similar to the one for T > TCO. Well into the insulating state, however, at T = 80 K, the spectral response evidences a completely different electronically-induced high-conducting state. Applying a two-state model of hot electrons explains the observations by excitation of charge carriers with a high mobility. They resemble the Dirac-like charge-carriers with a linear dispersion of the electronic bands found in α-(BEDT-TTF)2I3 at high-pressure. Extensive numerical simulations quantitatively reproduce our experimental findings in all details.

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Molecular Dynamics at Electrical- and Optical-Driven Phase Transitions: Time-Resolved Infrared Studies Using Fourier-Transform Spectrometers

Cited by 5 publications

References 77 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

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

Electrically induced phase transition inα−(BEDT-TTF)2I3: Indications for Dirac-like hot charge carriers

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