Ultrafast rotational motions of supported nanoclusters probed by electron diffraction

Vasileiadis, Thomas; Skountzos, Emmanuel N.; Foster, Dawn M.; Coleman, Shawn P.; Zahn, Daniela; Krecinic, Faruk; Mavrantzas, Vlasis G.; Palmer, Richard E.; Ernstorfer, Ralph

doi:10.1039/c9nh00031c

Cited by 11 publications

(16 citation statements)

References 35 publications

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“…To unravel the atomic motions behind the 1-THz oscillations in real space, we use an approach that combines RT-TDDFT with MDS. We show how this approach, which allows for a direct comparison with the FED experiments ( 37 , 38 ), is well suited given the complex vibrational structure of the pentacene crystal, featuring 108 phonon branches.…”

Section: Resultsmentioning

confidence: 99%

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Nuclear dynamics of singlet exciton fission in pentacene single crystals

et al. 2021

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Singlet exciton fission (SEF) is a key process for developing efficient optoelectronic devices. An aspect rarely probed directly, yet with tremendous impact on SEF properties, is the nuclear structure and dynamics involved in this process. Here, we directly observe the nuclear dynamics accompanying the SEF process in single crystal pentacene using femtosecond electron diffraction. The data reveal coherent atomic motions at 1 THz, incoherent motions, and an anisotropic lattice distortion representing the polaronic character of the triplet excitons. Combining molecular dynamics simulations, time-dependent density-functional theory, and experimental structure factor analysis, the coherent motions are identified as collective sliding motions of the pentacene molecules along their long axis. Such motions modify the excitonic coupling between adjacent molecules. Our findings reveal that long-range motions play a decisive part in the electronic decoupling of the electronically correlated triplet pairs and shed light on why SEF occurs on ultrafast time scales.

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Section: Resultsmentioning

confidence: 99%

“…Out-of-equilibrium MDS were obtained from microcanonical dynamics following a thermalization by a hotspot thermostat ( 39 ) centered at 1 THz. A connection to the FED experiments can be obtained by simulating diffraction patterns for each MDS snapshot ( 37 , 40 ), as illustrated in Fig. 3C .…”

Section: Resultsmentioning

confidence: 99%

Nuclear dynamics of singlet exciton fission in pentacene single crystals

et al. 2021

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“…Variants of FED have recently been used to study lattice dynamics in several other systems, including metals [38,39], semiconductors [34,40], heterostructures [41,42], and systems involving structural phase transitions [43,44]. We present an approach to characterize the transient lattice state, by converting Bragg reflection intensities into units of Kelvin, producing a series of temperatures associated with each scattering vector of the probe electrons (Q).…”

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Exchange-Striction Driven Ultrafast Nonthermal Lattice Dynamics in NiO

et al. 2021

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We use femtosecond electron diffraction to study ultrafast lattice dynamics in the highly correlated antiferromagnetic (AF) semiconductor NiO. Using the scattering vector (Q) dependence of Bragg diffraction, we introduce a Q-resolved effective lattice temperature, and identify a nonthermal lattice state with preferential displacement of O compared to Ni ions, which occurs within ~0.3 ps and persists for 25 ps. We associate this with transient changes to the AF exchange striction-induced lattice distortion, supported by the observation of a transient Q-asymmetry of Friedel pairs. Our observation highlights the role of spin-lattice coupling in routes towards ultrafast control of spin order.

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“…To unravel the atomic motions behind the 1 THz oscillations in real space, we employ an approach that combines RT-TDDFT with MDS. We show how this approach, which allows for a direct comparison with the FED experiments [40,41], is well-suited given the complex vibrational structure of the pentacene crystal, featuring 108 phonon branches.…”

Section: Resultsmentioning

confidence: 99%

“…Out-of-equilibrium MDS were obtained from microcanonical dynamics following a thermalization by a hotspot thermostat [42] centered at 1 THz. A connection to the FED experiments can be obtained by simulating diffraction patterns for each MDS snapshot [40,43], as in Figure 3(c). Figure 3(d) displays simulated Bragg peak intensities as a function of time in equilibrium for the (020) and (110) reflections.…”

Section: Theoretical Modelling: Nuclear Dynamicsmentioning

confidence: 99%

Nuclear dynamics of singlet exciton fission: a direct observation in pentacene single crystals

Seiler,

Krynski,

Zahn

et al. 2020

Preprint

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Ultrafast rotational motions of supported nanoclusters probed by electron diffraction

Abstract: Femtosecond electron diffraction is established as goniometer of ultrafast nanocrystal rotations.

Cited by 11 publications

References 35 publications

Nuclear dynamics of singlet exciton fission in pentacene single crystals

Nuclear dynamics of singlet exciton fission in pentacene single crystals

Exchange-Striction Driven Ultrafast Nonthermal Lattice Dynamics in NiO

Nuclear dynamics of singlet exciton fission: a direct observation in pentacene single crystals

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