Ultrafast transport and energy relaxation of hot electrons in Au/Fe/MgO(001) heterostructures analyzed by linear time-resolved photoelectron spectroscopy

Kühne, F.; Beyazit, Yasin; Sothmann, Björn; Jayabalan, J.; Diesing, Detlef; Zhou, Ping; Bovensiepen, Uwe

doi:10.1103/physrevresearch.4.033239

Cited by 8 publications

(12 citation statements)

References 32 publications

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“…Our results indicate that the dynamics resulting from electron–electron interactions cannot be consistently described with an energy-independent relaxation time. Generally, we observe the decay of electronic occupation further away from the Fermi edge on similar time scales as shown in photoemission measurements. ,, However, in experiments, single collision processes cannot be isolated, and the results are naturally influenced by electron–phonon interaction and other dissipation processes as transport mechanisms. ,, …”

Section: Resultssupporting

confidence: 70%

“…In many cases, the temporal evolution of the density of electrons within a certain energy window is of particular interest. Experimentally, such energy-resolved electron densities are accessible with, e.g., photoemission spectroscopy. , We determine theoretically these spectral electron densities from the time- and energy-dependent distribution as n E c , normalΔ E ( t ) = ∫ E c − normalΔ E / 2 E c + normalΔ E / 2 f ( E , t ) .25em D ( E ) .25em normald E yielding the density of electrons in an energy interval of width Δ E centered around a central energy E c .…”

Section: Resultsmentioning

confidence: 99%

“…Experimentally, such energy-resolved electron densities are accessible with, e.g., photoemission spectroscopy. 16,62 We determine theoretically these spectral electron densities from the time-and energydependent distribution as…”

Section: The Journal Of Physical Chemistrymentioning

confidence: 99%

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Time-Resolved Spectral Densities of Nonthermal Electrons in Gold

Seibel,

Uehlein,

Held

et al. 2023

J. Phys. Chem. C

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Noble-metal nanoparticles for photocatalysis have become a major research object in recent years due to their plasmon-enhanced strong light−matter interaction. The dynamics of the hot electrons in the noble metal is crucial for the efficiency of the photocatalysis and for the selective control of reactions. In this work, we present a kinetic description of the nonequilibrium electron distribution created by photoexcitation based on full energy-resolved Boltzmann collision integrals for the laser excitation as well as for the electron−electron thermalization. The laser-induced electronic nonequilibrium and the inherently included secondary electron generation govern the dynamics of nonthermal electrons. Applying our method to gold, we show a significant dependence of hot electron dynamics on the kinetic energy. Specifically, the time scales of the relaxation as well as the qualitative behavior are dependent on the evaluated energy window. During the thermalization processes, there are cases of increasing electron density as well as of decreasing electron density. Studying the influence of excitation parameters, we find that the photon energy and the fluence of the exciting laser can be tuned to influence not only the initial excitation but also the subsequent characteristics of the time-resolved electronic spectral density dynamics. The electronic thermalization including secondary electron generation leads to time-dependent spectral densities, which differ from their specific final equilibrium values for picoseconds after irradiation ended.

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

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Time-Resolved Spectral Densities of Nonthermal Electrons in Gold

Seibel,

Uehlein,

Held

et al. 2023

J. Phys. Chem. C

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“…Reducing the frustration of the electron density induced by the non-thermal population, this process in turn gives rise to the slowly evolving thermal contribution (dashed lines in Figure ). The found time scale τ 2 ≈ 840 ± 55 fs agrees well with the relaxation times of the non-thermal electron population in Au reported in multiple works. ,,,− The picosecond time scale is dominated by the relaxation of the electronic density to the Fermi–Dirac equilibrium albeit at an elevated temperature. It can thus be construed that the first and second terms in eq are dominated by the non-thermal ( A ) and thermal ( B ) electron-induced contributions, respectively.…”

supporting

confidence: 87%

“…The exact time scale, however, is distorted by the initial distribution of the hot-laser-excited electrons in the k-space and the exponentially decaying SPP sensitivity to the depth distribution of the perturbation. 28,37 The superdiffusive nature of the nonthermal electron transport is nonetheless strongly emphasized by the experimentally found delay t(ΔR/R| max ) value of t max ≈ 350 fs.…”

mentioning

confidence: 99%

Ultrafast Laser-Induced Dynamics of Non-Equilibrium Electron Spill-Out in Nanoplasmonic Bilayers

Avdizhiyan,

Janus,

Szpytma

et al. 2023

Nano Lett.

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Contemporary quantum plasmonics capture subtle corrections to the properties of plasmonic nano-objects in equilibrium. Here, we demonstrate nonequilibrium spill-out redistribution of the electronic density at the ultrafast time scale. As revealed by time-resolved 2D spectroscopy of nanoplasmonic Fe/Au bilayers, an injection of the laser-excited non-thermal electrons induces transient electron spill-out thus changing the plasma frequency. The response of the local electronic density switches the electronic density behavior from spill-in to strong (an order of magnitude larger) spill-out at the femtosecond time scale. The superdiffusive transport of hot electrons and the lack of a direct laser heating indicate significantly non-thermal origin of the underlying physics. Our results demonstrate an ultrafast and non-thermal way to control surface plasmon dispersion through transient variations of the spatial electron distribution at the nanoscale. These findings expand quantum plasmonics into previously unexplored directions by introducing ultrashort time scales in the non-equilibrium electronic systems.

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Concerted Mechanism of Carrier Dynamics in Laser‐Excited Fe_n/(MgO)_m(001) Heterostructures from Real‐Time Time‐Dependent DFT

Shomali,

Gruner,

Pentcheva

2023

Advcd Theory and Sims

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Using real‐time time‐dependent density functional theory (RT‐TDDFT), the electronic response of a Fen/(MgO)m(001) (n=1,3,5 and m=3,5,7) metal/insulator heterostructure to an optical excitation is calculated, considering laser frequencies below, near, and above the bandgap of the insulator and two directions of polarization. The spatial redistribution of electronic charge after illumination shows a strong dependence on the frequency and polarization direction of the laser pulse with a similar pattern for all thicknesses. The comparison of the layer‐resolved changes in occupation of the ground‐state orbitals after optical excitation obtained for Fen/(MgO)m(001) and bulk Fe reveals the origin of excited carriers in the heterostructures: In the central and interface Fe layers carriers are excited from states in the vicinity of the Fermi‐level to the conduction band of MgO. Simultaneously, excitations take place from the valence band of MgO to Fe states above the Fermi‐level. This concerted mechanism allows for an effective bidirectional relocation of excited carriers between the metallic and insulating subsystems in heterostructures with a thickness of several nanometers, providing an effective accumulation of hot carriers in the insulating layers, even at photon energies in the vicinity and below the bandgap of bulk MgO.

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Ultrafast transport and energy relaxation of hot electrons in Au/Fe/MgO(001) heterostructures analyzed by linear time-resolved photoelectron spectroscopy

Cited by 8 publications

References 32 publications

Time-Resolved Spectral Densities of Nonthermal Electrons in Gold

Time-Resolved Spectral Densities of Nonthermal Electrons in Gold

Ultrafast Laser-Induced Dynamics of Non-Equilibrium Electron Spill-Out in Nanoplasmonic Bilayers

Concerted Mechanism of Carrier Dynamics in Laser‐Excited Fe_n/(MgO)_m(001) Heterostructures from Real‐Time Time‐Dependent DFT

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Ultrafast transport and energy relaxation of hot electrons in Au/Fe/MgO(001) heterostructures analyzed by linear time-resolved photoelectron spectroscopy

Cited by 8 publications

References 32 publications

Time-Resolved Spectral Densities of Nonthermal Electrons in Gold

Time-Resolved Spectral Densities of Nonthermal Electrons in Gold

Ultrafast Laser-Induced Dynamics of Non-Equilibrium Electron Spill-Out in Nanoplasmonic Bilayers

Concerted Mechanism of Carrier Dynamics in Laser‐Excited Fen/(MgO)m(001) Heterostructures from Real‐Time Time‐Dependent DFT

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Product

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Concerted Mechanism of Carrier Dynamics in Laser‐Excited Fe_n/(MgO)_m(001) Heterostructures from Real‐Time Time‐Dependent DFT