Electron-phonon equilibration in laser-heated gold films

Abstract

By irradiating a thin metal foil with an intense short-pulse laser, we have created a uniform system far from equilibrium. The deposited energy is initially deposited only within the electronic subsystem, and the subsequent evolution of the system is determined by the details of the electron-phonon coupling. Here, we measure the time evolution of the lattice parameter through multilayer Bragg diffraction and compare the result to classical molecular dynamic simulations to determine the lattice temperature. The electron-ion coupling constant for gold is then determined by comparison with the evolution of a two-temperature electron-phonon system.

Atomistic simulation of laser-pulse surface modification: Predictions of models with various length and time scales

“…In this work, the selection of g is based on a value averaged over the data from several works. 14,35,40 However, the given values of g must be regarded as an estimation.…”

“…Absorption of the laser pulse initially leads to excitation of the electron subsystem (ES). [12][13][14] In this case, initial state of the system is the two-temperature (2T) state, and the electron temperature (T e ) may be several orders higher than the ion temperature (T i ). The time of electron-ion relaxation is comparable to the time of relaxation processes taking place in the ion subsystem (IS) such as heat transfer and phase transitions.…”

Density response to short‐pulse excitation in gold

“…In particular, the use of lasers with femtosecond pulses has brought a new set of fundamental questions regarding the nature of the interaction process and the evolution of the material response . Such short excitations drive a whole cascade of relaxation processes starting from the electron kinetics to the equilibration of electron and lattice temperatures, with most of the associated relaxation rates being still under debate even for noble metals . Moreover, the basic material properties, such as the lattice stabilities and phonon modes, can change under laser irradiation .…”

Communication: Demonstration of a 20 ps X-ray switch based on a photoacoustic transducer

“…The values of G in the literature span from 2 × 10 16 to 1 × 10 17  W m −3 K −1 depending on the electronic temperature, 24 the experimental technique, 31 or the nature of the substrate 32 . The electron-phonon equilibration time is related to the coupling factor by the relation 33 $t_{eq}=A_e{T}_e/G$, where T e  = 5400 K is the maximum initial electronic temperature. For G  = 4 × 10 16  W m −3 K −1 , this corresponds to t eq ∼ 9 ps which in our case is faster than the acoustic propagation time through the Au film $t_{ac}=d_{Au}/c_{s,Au}\sim 19$ ps.…”