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.

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.

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

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.

Influence of Inter- and Intraband Transitions to Electron Temperature Decay in Noble Metals After Short-Pulsed Laser Heating

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Patrick E. Hopkins
Keyword(s):  
Heat Capacity ◽  
Electron Temperature ◽  
Noble Metals ◽  
Coupling Factor ◽  
Phonon Coupling ◽  
Electron Heat Capacity ◽  
Temperature Decay ◽  
Electron Heat ◽  
Electron Phonon Coupling ◽  
Pulsed Laser Heating

This work examines the effects of photonically induced interband excitations from the d-band to states at the Fermi energy on the electron temperature decay in noble metals. The change in the electron population in the d-band and the conduction band causes a change in electron heat capacity and electron-phonon coupling factor. In noble metals, due to the large d-band to Fermi energy separation, the contributions to electron heat capacity and electron-phonon coupling factor of intra- and interband transitions can be separated. The two temperature model describing electron-phonon heat transfer after short-pulsed laser heating is solved using the expressions for heat capacity and electron-phonon coupling factor after intra- and interband excitations, and the predicted electron temperature change of the intra- and interband excited electrons are examined. A critical fluence value is defined that represents the absorbed fluence needed to fill all available states at a given photon energy above the Fermi level. At high absorbed laser fluences and pulse energies greater than the interband transition threshold, the interband and intraband contributions to thermophysical properties differ and are shown to affect temporal electron temperature profiles.

Two Temperature Model Numerical Simulation and Analysis of Thermal Transport Process in Copper Film

2013 ◽  
Vol 750-752 ◽  
pp. 2271-2274
Author(s):  
Fan Da Zeng ◽  
Ya Ping Han ◽  
Jin Xin Wang ◽  
Shao Ze Wang
Keyword(s):  
Thermal Transport ◽  
Transport Process ◽  
Copper Film ◽  
Coupling Factor ◽  
Beam Power ◽  
Temperature Model ◽  
Laser Beam Power ◽  
Lattice Coupling ◽  
Two Temperature ◽  
Pump Laser Beam

Thermal transport process in copper film was numerically simulated with Two-Temperature Model, in which finite difference method was used, and the result shown the temperature change process in electron-lattice system. Some parameters were changed to carry on further simulation. The affect of film thickness on the electronic relaxation time was analyzed. The affect of pump laser beam power on the electron temperature rise was discussed. The influence of electron-lattice coupling factor G on non-equilibrium thermal process was shown in simulations.

Electron–phonon coupling factor and electron heat capacity of 6H-SiC

2021 ◽  
pp. 1-8
Author(s):  
Wenlong Liao ◽  
Chaohui He ◽  
Huan He ◽  
Shang Tian ◽  
Yurong Bai
Keyword(s):  
Heat Capacity ◽  
Coupling Factor ◽  
Phonon Coupling ◽  
Electron Heat Capacity ◽  
Electron Heat ◽  
Electron Phonon Coupling
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