Ultrafast lattice dynamics and electron–phonon coupling in platinum extracted with a global fitting approach for time-resolved polycrystalline diffraction data

Zahn, Daniela; Seiler, H.; Windsor, Yoav William; Ernstorfer, Ralph

doi:10.1063/4.0000120

Cited by 11 publications

(5 citation statements)

References 47 publications

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“…The latter was estimated to be only about 2 K for an excitation density of 2.8 × 10 19 cm –3 (see Supporting Information). Thermal heating leads to an intensity decrease of all Bragg peaks as per the Debye–Waller effect; see for instance ref . Such a response is clearly not observed here for peaks 1, 2, and 4.…”

Section: Resultsmentioning

confidence: 47%

Direct Observation of Ultrafast Lattice Distortions during Exciton–Polaron Formation in Lead Halide Perovskite Nanocrystals

et al. 2023

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The microscopic origin of slow hot-carrier cooling in lead halide perovskites remains debated and has direct implications for applications. Slow hot-carrier cooling of several picoseconds has been attributed to either polaron formation or a hot-phonon bottleneck effect at high excited carrier densities (>1018 cm–3). These effects cannot be unambiguously disentangled with optical experiments alone. However, they can be distinguished by direct observations of ultrafast lattice dynamics, as these effects are expected to create qualitatively distinct fingerprints. To this end, we employ femtosecond electron diffraction and directly measure the sub-picosecond lattice dynamics of weakly confined CsPbBr3 nanocrystals following above-gap photoexcitation. While we do not observe signatures of a hot-phonon bottleneck lasting several picoseconds, the data reveal a light-induced structural distortion appearing on a time scale varying between 380 and 1200 fs depending on the excitation fluence. We attribute these dynamics to the effect of exciton–polarons on the lattice and the slower dynamics at high fluences to slower sub-picosecond hot-carrier cooling, which slows down the establishment of the exciton–polaron population. Further analysis and simulations show that the distortion is consistent with motions of the [PbBr3]− octahedral ionic cage, and closest agreement with the data is obtained for Pb–Br bond lengthening. Our work demonstrates how direct studies of lattice dynamics on the sub-picosecond time scale can discriminate between competing scenarios proposed in the literature to explain the origin of slow hot-carrier cooling in lead halide perovskites.

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Section: Resultsmentioning

confidence: 47%

Direct Observation of Ultrafast Lattice Distortions during Exciton–Polaron Formation in Lead Halide Perovskite Nanocrystals

et al. 2023

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“…Instead, it becomes necessary in aluminum to separately account for the partial electron–phonon coupling to investigate the energy flow evolution. However, it seems the findings in aluminum cannot be generalized easily as further femtosecond electron diffraction experiments show different results [ 39 , 40 , 43 ]. Thus, accurate electron–phonon coupling factors for a wide variety of elements and materials are in high demand.…”

Section: Introductionmentioning

confidence: 99%

Energy Relaxation and Electron–Phonon Coupling in Laser-Excited Metals

et al. 2022

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The rate of energy transfer between electrons and phonons is investigated by a first-principles framework for electron temperatures up to Te = 50,000 K while considering the lattice at ground state. Two typical but differently complex metals are investigated: aluminum and copper. In order to reasonably take the electronic excitation effect into account, we adopt finite temperature density functional theory and linear response to determine the electron temperature-dependent Eliashberg function and electron density of states. Of the three branch-dependent electron–phonon coupling strengths, the longitudinal acoustic mode plays a dominant role in the electron–phonon coupling for aluminum for all temperatures considered here, but for copper it only dominates above an electron temperature of Te = 40,000 K. The second moment of the Eliashberg function and the electron phonon coupling constant at room temperature Te=315 K show good agreement with other results. For increasing electron temperatures, we show the limits of the T=0 approximation for the Eliashberg function. Our present work provides a rich perspective on the phonon dynamics and this will help to improve insight into the underlying mechanism of energy flow in ultra-fast laser–metal interaction.

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“…In the case of a magnetic insulator, laser‐excited hot electrons in the metal layer (Pt) get spin‐polarized upon scattering off the interface toward the magnetic insulator. [ 57 ] In α ‐Fe 2 O 3 /Pt, the electronic temperature of the Pt layer increases by Δ T Pt (t) upon laser excitation, [ 58,59 ] while that of the α ‐Fe 2 O 3 layer remains unaffected because of the weak absorption. [ 60 ] Therefore, the ultrafast‐SSE spin current injected from the α ‐Fe 2 O 3 to the Pt layer can be expressed as the temporal convolution

{J}_{y}^{\mathrm{s},{\Delta}\mathrm{T}}\ (t)=({\kappa}_{y}^{\mathrm{Pt}}\ast {\Delta}{T}^{\mathrm{Pt}})\ (t)

, with

\kappa _y^{{\rm{Pt}}}( t )

being the response function that relates the spin current in the Pt layer to an ultrashort δ ‐like temperature increase of the Pt electrons.…”

Section: Results and Analysismentioning

confidence: 99%

Terahertz Spin Current Dynamics in Antiferromagnetic Hematite

et al. 2023

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An important vision of modernmagnetic research is to use antiferromagnets (AFMs) as controllable and active ultrafast components in spintronic devices. Hematite (𝜶-Fe 2 O 3 ) is a promising model material in this respect because its pronounced Dzyaloshinskii-Moriya interaction leads to the coexistence of antiferromagnetism and weak ferromagnetism. Here, femtosecond laser pulses are used to drive terahertz (THz) spin currents from 𝜶-Fe 2 O 3 into an adjacent Pt layer. Two contributions to the generation of the spin current with distinctly different dynamics are found: the impulsive stimulated Raman scatting that relies on the AFM order and the ultrafast spin Seebeck effect that relies on the net magnetization. The total THz spin current dynamics can be manipulated by a medium-strength magnetic field below 1 T. The control of the THz spin current achieved in 𝜶-Fe 2 O 3 opens the pathway toward tailoring the exact spin current dynamics from ultrafast AFM spin sources.

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Ultrafast lattice dynamics and electron–phonon coupling in platinum extracted with a global fitting approach for time-resolved polycrystalline diffraction data

Cited by 11 publications

References 47 publications

Direct Observation of Ultrafast Lattice Distortions during Exciton–Polaron Formation in Lead Halide Perovskite Nanocrystals

Direct Observation of Ultrafast Lattice Distortions during Exciton–Polaron Formation in Lead Halide Perovskite Nanocrystals

Energy Relaxation and Electron–Phonon Coupling in Laser-Excited Metals

Terahertz Spin Current Dynamics in Antiferromagnetic Hematite

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