Out-of-equilibrium lattice response to photo-induced charge-transfer in a MnFe Prussian blue analogue - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Materials Chemistry C Année : 2021

Out-of-equilibrium lattice response to photo-induced charge-transfer in a MnFe Prussian blue analogue

Giovanni Azzolina
Roman Bertoni
Céline Mariette
Marco Cammarata
Elzbieta Trzop
Claude Ecolivet
K. Imoto
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S. Ohkoshi
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Résumé

Photo-induced structural dynamics in molecular materials often involve two main components; local molecular distortions induced by the self-trapping of electronic excited state and incoherent lattice dynamics due to energy dissipation. The latter component frequently hinders clear manifestation at macroscopic scale of local self-trapped entities and their coupling to the lattice. The studied photoactive MnFe Prussian blue analogue exhibits no thermal expansion, which allows observing long-range lattice dynamics induced by the structural trapping of photo-induced charge-transfer (CT) states. The self-trapping of the photo-induced (MnFeII)-Fe-III -> (MnFeIII)-Fe-II is responsible for the emergence of various physical properties. At equilibrium, the lattice volume expansion and the ferroelastic Jahn-Teller distortion associated with the charge-transfer-based phase transition, evolve in a coupled way. Here, we use time resolved X-ray diffraction to investigate the anisotropic out-of-equilibrium lattice dynamics triggered by the self-trapping of photo-induced (MnFeII)-Fe-III -> (MnFeIII)-Fe-II CT. The observed dynamics evidence a decoupling of both types of lattice deformations in the time domain, with an impulsive lattice response driven by the local Jahn-Teller reorganization and a displacive volume expansion controlled by the long-lived photo-induced CT small-polarons, due to the population of antibonding orbitals centered on Mn-N bonds in the (a,b) lattice plane.
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Dates et versions

hal-03244969 , version 1 (01-06-2021)

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Giovanni Azzolina, Roman Bertoni, Céline Mariette, Marco Cammarata, Elzbieta Trzop, et al.. Out-of-equilibrium lattice response to photo-induced charge-transfer in a MnFe Prussian blue analogue. Journal of Materials Chemistry C, 2021, 9 (21), pp.6773-6780. ⟨10.1039/d1tc01487k⟩. ⟨hal-03244969⟩
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