scholarly journals Tracking ultrafast hot-electron diffusion in space and time by ultrafast thermomodulation microscopy

2019 ◽  
Vol 5 (5) ◽  
pp. eaav8965 ◽  
Author(s):  
A. Block ◽  
M. Liebel ◽  
R. Yu ◽  
M. Spector ◽  
Y. Sivan ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Nonequilibrium Dynamics ◽  
Hot Electron ◽  
Temperature Model ◽  
Three Dimensional Model ◽  
Electron Diffusion ◽  
Diffusion Dynamics ◽  
Electron Phonon Coupling ◽  
20 Nm ◽  
Two Temperature

The ultrafast response of metals to light is governed by intriguing nonequilibrium dynamics involving the interplay of excited electrons and phonons. The coupling between them leads to nonlinear diffusion behavior on ultrashort time scales. Here, we use scanning ultrafast thermomodulation microscopy to image the spatiotemporal hot-electron diffusion in thin gold films. By tracking local transient reflectivity with 20-nm spatial precision and 0.25-ps temporal resolution, we reveal two distinct diffusion regimes: an initial rapid diffusion during the first few picoseconds, followed by about 100-fold slower diffusion at longer times. We find a slower initial diffusion than previously predicted for purely electronic diffusion. We develop a comprehensive three-dimensional model based on a two-temperature model and evaluation of the thermo-optical response, taking into account the delaying effect of electron-phonon coupling. Our simulations describe well the observed diffusion dynamics and let us identify the two diffusion regimes as hot-electron and phonon-limited thermal diffusion, respectively.

Understanding the sensitivity of the two-temperature model for electron–phonon coupling measurements

2020 ◽  
Vol 128 (8) ◽  
pp. 085102
Author(s):  
Sarah B. Naldo ◽  
Andrius V. Bernotas ◽  
Brian F. Donovan
Keyword(s):  
Temperature Model ◽  
Phonon Coupling ◽  
Electron Phonon Coupling ◽  
Two Temperature

Influence of the Probe Laser Wavelength in Transient Reflectance Measurement of Gold

2014 ◽  
Author(s):  
Liang Guo ◽  
Xianfan Xu
Keyword(s):  
Electron Excitation ◽  
Coupling Factor ◽  
Laser Wavelength ◽  
Probe Laser ◽  
Temperature Model ◽  
Reflectance Measurement ◽  
Probe Wavelength ◽  
Electron Phonon Coupling ◽  
Reflectance Change ◽  
Two Temperature

Transient reflectance of gold is measured with ultrafast spectroscopy by tunable probe wavelength. The influence of the probe wavelength on the signal is analyzed. It is found that when probed around 490 nm the signal is most sensitive to electron excitation and there is a simple linear relation between the reflectance change and the electron temperature change after sufficiently weak excitation. The two-temperature model is applied to calculate the electron-phonon coupling factor by fitting the transient reflectance signal.

scholarly journals Ultrastructure of the proximal region of somatic cilia in Paramecium tetraurelia.

1978 ◽  
Vol 78 (2) ◽  
pp. 451-464 ◽  
Author(s):  
R Dute ◽  
C Kung
Keyword(s):  
Transition Zone ◽  
Membrane Surface ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Proximal Region ◽  
Paramecium Tetraurelia ◽  
Three Dimensional Model ◽  
Anionic Sites ◽  
Ciliary Beating ◽  
20 Nm

The morphology of the transition zone between the terminal plate of the basal body and the 9 + 2 region of the somatic (non-oral) cilium has been examined in Paramecium tetraurelia. Freeze-fracture and thin-section techniques disclosed both membrane specializations and various internal structural linkages. Freeze-fracture material revealed sets of particles interrupting the unit membrane. The more distal of these form plaquelike arrays while the proximal set of particles forms the ciliary "necklace." The plaque regions correspond to anionic sites on the outer membrane surface as revealed by binding of polycationic ferritin. Both the plaque particles and the necklace particles appear to be in contact with outer doublet microtubules via a complex of connecting structures. In the interior of the transition zone an axosomal plate supports an axosome surrounded by a ring of lightly packed material. Only one of the two central tubules of the axoneme reaches and penetrates the axosome. Below the axosomal plate four rings, each approx. 20 nm wide, connect adjacent outer doublets. An intermediate plate lies proximal to these rings, and a terminal plate marks the proximal boundary of this zone. Nine transitional fibers extend from the region of the terminal plate to the plasmalemma. The observations described above have been used to construct a three-dimensional model of the transition region of "wild-type" Paramecium somatic cilia. It is anticipated that this model will be useful in future studies concerning possible function of transition-zone specializations, since Paramecium may be examined in both normal and reversed ciliary beating modes, and since mutants incapable of reverse beating are available.

An improved three-dimensional two-temperature model for multi-pulse femtosecond laser ablation of aluminum

2015 ◽  
Vol 117 (6) ◽  
pp. 063104 ◽  
Author(s):  
Jinping Zhang ◽  
Yuping Chen ◽  
Mengning Hu ◽  
Xianfeng Chen
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Three Dimensional ◽  
Femtosecond Laser Ablation ◽  
Temperature Model ◽  
Two Temperature

Ultrafast Spectroscopy of Electron-Phonon Coupling in Gold

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Liang Guo ◽  
Xianfan Xu
Keyword(s):  
Ultrafast Spectroscopy ◽  
Coupling Factor ◽  
Laser Wavelength ◽  
Heat Transfer Process ◽  
Probe Laser ◽  
Visible Range ◽  
Temperature Model ◽  
Phonon Coupling ◽  
Electron Phonon Coupling ◽  
Two Temperature

Transient reflectance of gold was measured using ultrafast spectroscopy by varying the wavelength of the probe laser beam in the visible range. Based on the band structure of gold, the influence of the probe beam wavelength on the signal trend is analyzed in terms of sensitivity, effect of nonthermalized electrons, and relaxation rate. It is found that probing around 490 nm renders the best sensitivity and a simple linear relation between the transient reflectance and the electron temperature. The two-temperature model (TTM) is applied to calculate the electron-phonon coupling factor by fitting the transient reflectance signal. This work clarifies the ultrafast energy transfer dynamics in gold and the importance of using proper probe laser wavelength for modeling the transient heat transfer process in metal.

Temperature and pressure dependence of the optical gaps in Hf1−xZrxS2

1988 ◽  
Vol 66 (7) ◽  
pp. 633-637 ◽  
Author(s):  
Larbi Roubi ◽  
Cosmo Carlone
Keyword(s):  
Three Dimensional ◽  
Volume Effect ◽  
Electronic Energy ◽  
Coupling Constant ◽  
Indirect Transition ◽  
Three Dimensional Model ◽  
Intrinsic Volume ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Layered Crystals

Mixed layered crystals of the type Hf1−xZrxS2, with x = 0.0, 0.1, 0.25, 0.5, 0.75, 0.90, and 1.0, have been grown by the iodine transport method. The direct (at the Γ points) and indirect (Γ to L) transitions have been measured (at T = 290 K) as a function of pressure from 0 to 30 kbar, and (at p = 0 kbar) as a function of the temperature (15–290 K). The phonon frequency assisting the indirect transition is 40 ± 2 MeV. The intrinsic (volume effect) and extrinsic (interaction effect) contributions to the change in electronic energy have been evaluated. We find that the electron–phonon interaction is more aptly described by a quasi-three-dimensional model than a purely two-dimensional one. From the shift of the indirect gap, we find that the electron–phonon coupling constant g varies linearly from 0.54 ± 0.03 (x = 0) to 0.44 ± 0.03 (x = 1.0).

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