We have studied the mechanism of coherent acoustic phonon generation in gold nanofilm induced by ultrafast laser-heating. Under the non-equilibrium condition when the lattice heating time is much longer than the film vibration period, we clearly identified the contribution of electronic thermal stress to drive the lattice motion and successfully measured the electronic Grüneisen parameter γe to be 1.6 ± 0.3. We also found that lattice heating via the electron–phonon coupling process lagged behind the coherent lattice motion, which we attributed to the prolonged thermalization process of the laser-excited non-thermal electrons under high pumping conditions. By taking such a process into account, the improved model fit our experimental data much better, and the extracted γe of gold was still around 1.6.
REFERENCES
1.
P.
Ruello
and V.
Gusev
, “Physical mechanisms of coherent acoustic phonons generation by ultrafast laser action
,” Ultrasonics
56
, 21
–35
(2015
).2.
W. S.
Fann
, R.
Storz
, H. W. K.
Tom
, and J.
Bokor
, “Direct measurement of nonequilibrium electron-energy distributions in subpicosecond laser-heated gold films
,” Phys. Rev. Lett.
68
(18
), 2834
–2837
(1992
).3.
R. H. M.
Groeneveld
, R.
Sprik
, and Ad.
Lagendijk
, “Femtosecond spectroscopy of electron-electron and electron-phonon energy relaxation in Ag and Au
,” Phys. Rev. B
51
(17
), 11433
–11445
(1995
).4.
N.
Del Fatti
, C.
Voisin
, M.
Achermann
, S.
Tzortzakis
, D.
Christofilos
, and F.
Vallée
, “Nonequilibrium electron dynamics in noble metals
,” Phys. Rev. B
61
(24
), 16956
–16966
(2000
).5.
J.
Hohlfeld
, S. S.
Wellershoff
, J.
Gudde
, U.
Conrad
, V.
Jahnke
, and E.
Matthias
, “Electron and lattice dynamics following optical excitation of metals
,” Chem. Phys.
251
, 237
–258
(2000
).6.
G.
Tas
and H. J.
Maris
, “Electron diffusion in metals studied by picosecond ultrasonics
,” Phys. Rev. B
49
(21
), 15046
–15054
(1994
).7.
M.
Perner
, S.
Gresillon
, J.
März
, G.
von Plessen
, J.
Feldmann
, J.
Porstendorfer
, K.-J.
Berg
, and G.
Berg
, “Observation of hot-electron pressure in the vibration dynamics of metal nanoparticles
,” Phys. Rev. Lett.
85
(4
), 792
–795
(2000
).8.
J.
Wang
and C.
Guo
, “Effect of electron heating on femtosecond laser-induced coherent acoustic phonons in noble metals
,” Phys. Rev. B
75
(18
), 184304
(2007
).9.
O. B.
Wright
, “Ultrafast nonequilibrium stress generation in gold and silver
,” Phys. Rev. B
49
(14
), 9985
–9988
(1994
).10.
X.
Wang
, S.
Nie
, J.
Li
, R.
Clinite
, M.
Wartenbe
, M.
Martin
, W.
Liang
, and J.
Cao
, “Electronic gruneisen parameter and thermal expansion in ferromagnetic transition metal
,” Appl. Phys. Lett.
92
(12
), 121918
(2008
).11.
S.
Nie
, X.
Wang
, H.
Park
, R.
Clinite
, and J.
Cao
, “Measurement of the electronic gr[u-umlaut]neisen constant using femtosecond electron diffraction
,” Phys. Rev. Lett.
96
(2
), 025901
(2006
).12.
M.
Nicoul
, U.
Shymanovich
, A.
Tarasevitch
, D.
von der Linde
, and K.
Sokolowski-Tinten
, “Picosecond acoustic response of a laser-heated gold-film studied with time-resolved x-ray diffraction
,” Appl. Phys. Lett.
98
, 191902
(2011
).13.
J. G.
Collins
, G. K.
White
, and C. A.
Swenson
, “The thermal expansion of aluminum below 35 K
,” J. Low Temp. Phys.
10
, 69
–77
(1973
).14.
T. H. K.
Barron
, J. G.
Collins
, and G. K.
White
, “Thermal expansion of solids at low temperatures
,” Adv. Phys.
29
, 609
–730
(1980
).15.
H.
Park
, X.
Wang
, S.
Nie
, R.
Clinite
, and J.
Cao
, “Mechanism of coherent acoustic phonon generation under nonequilibrium conditions
,” Phys. Rev. B
72
(10
), 100301
(2005
).16.
K. O.
Mclean
, C. A.
Swenson
, and C. R.
Case
, “Thermal expansion of copper, silver, and gold below 30 K
,” J. Low Temp. Phys.
7
, 77
–98
(1972
).17.
X.
Wang
, H.
Park
, S.
Nie
, and J.
Cao
, “Femtosecond electron diffraction: Probe and control of ultrafast structural dynamics
,” Microsc. Microanal.
11
, 478
(2005
).18.
X.
Wang
and Y.
Li
, “Ultrafast electron diffraction
,” Chin. Phys. B
27
(7
), 076102
(2018
).19.
D. B.
Sirdeshmukh
, L.
Sirdeshmukh
, and K. G.
Subhadra
, Micro- and Macro-Properties of Solids
(Springer
, 2006
).20.
P. B.
Allen
, “Theory of thermal relaxation of electrons in metals
,” Phys. Rev. Lett.
59
(13
), 1460
–1463
(1987
).21.
L.
Waldecker
, R.
Bertoni
, R.
Ernstorfer
, and J.
Vorberger
, “Electron-phonon coupling and energy flow in a simple metal beyond the two-temperature approximation
,” Phys. Rev. X
6
(2
), 021003
(2016
).22.
M.
Ligges
, I.
Rajkovic
, P.
Zhou
, O.
Posth
, C.
Hassel
, G.
Dumpich
, and D.
Von Der Linde
, “Observation of ultrafast lattice heating using time resolved electron diffraction
,” Appl. Phys. Lett.
94
(10
), 101910
(2009
).23.
J.
Li
, R.
Clinite
, X.
Wang
, and J.
Cao
, “Simulation of ultrafast heating induced structural dynamics using a one-dimensional spring model
,” Phys. Rev. B
80
, 014304
(2009
).24.
S. D.
Brorson
, J. G.
Fujimoto
, and E. P.
Ippen
, “Femtosecond electronic heat-transport dynamics in thin gold films
,” Phys. Rev. Lett.
59
(17
), 1962
– 1965
(1987
).25.
Z.
Lin
, L. V.
Zhigilei
, and V.
Celli
, “Electron-phonon coupling and electron heat capacity of metals under conditions of strong electron-phonon nonequilibrium
,” Phys. Rev. B
77
(7
), 075133
(2008
).26.
Y.
Takahashi
and H.
Akiyama
, “Heat capacity of gold from 80 to 1000 K
,” Thermochim. Acta
109
(1
), 105
–109
(1986
).27.
G.
Cordoba
and C. R.
Brooks
, “The heat capacity of gold from 300 to 1200 K: Experimental data and analysis of contributions
,” Phys. Status Solidi A
6
(2
), 581
–595
(1971
).28.
D. R.
Lide
, CRC Handbook Chemistry and Physics
, 82nd ed. (Chemical Rubber Company
, Roca Raton
, 2001–2002
).© 2020 Author(s).
2020
Author(s)
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