Exploring Ultrafast Photoswitching Pathways in RbMnFe Prussian Blue Analogue

Abstract

We study by femtosecond optical pump‐probe spectroscopy the photoinduced charge transfer (CT) in the RbMnFe Prussian blue analogue. Previous studies evidenced the local nature of the photoinduced MnIIIFeII → MnIIFeIII process, occurring within less than 1 ps. Here we show experimentally that two photoswitching pathways exist, depending on the excitation pump wavelength, which is confirmed by band structure calculations. Photoexcitation of α spins corresponds to the Mn(d‐d) band, which drives reverse Jahn–Teller distortion through the population of antibonding Mn‐N orbitals, and induces CT within ≈190 fs. The process launches coherent lattice torsion during the self‐trapping of the CT small‐polaron. Photoexcitation of β spins drives intervalence Fe→Mn CT towards non‐bonding states and results in a slower dynamic.

Optical Phenomena in Molecule-Based Magnetic Materials

“…Copyright 2008 American Chemical Society. Part (f) was adapted with permission from ref . Copyright 2021 John Wiley & Sons.…”

“…The charge transfer process for the RbMnFe PBA was also studied using femtosecond light pulses (Figure 18f). 562 For that purpose, two excitation wavelengths were selected, 445 nm and 580 nm, corresponding to the intervalence (IT) charge transfer and Mn III -centered d−d absorption bands, respectively, while time evolution of the optical density charge was collected at 640 nm. The performed analysis revealed two separate processes depending on the excitation light.…”

“…Then the 410 nm light irradiation recovers the initial low-temperature state almost quantitively. The charge transfer process for the RbMnFe PBA was also studied using femtosecond light pulses (Figure f) . For that purpose, two excitation wavelengths were selected, 445 nm and 580 nm, corresponding to the intervalence (IT) charge transfer and Mn III -centered d–d absorption bands, respectively, while time evolution of the optical density charge was collected at 640 nm.…”