Abstract

Ultrafast laser-excited hot electrons in metals can transport energy supersonically far from the region where they are initially produced. We show that this ultrafast energy transport is responsible for the emission of coherent acoustic phonons deep beneath the free surface of a weak electron–phonon coupling copper metal sample. Special attention is taken to investigate the interaction between superdiffusive hot electrons at the bi-metallic buried interface (Cu–Ti). To discuss the underlying physics and the ultrafast transient optical properties, several configurations developed in the frame of ultrafast optical pump–probe technique have been used. In particular, we have performed backward and forward detection of both coherent acoustic phonons and superdiffusive hot electrons. From an original probe wavelength dependence study of the optical detection process, we clearly establish the signature of superdiffusive hot transport within the copper film and the link with the acoustic phonon emission. A comparison with a strong electron–phonon coupling metal, like titanium, where there is no superdiffusive transport is also provided. These results and observations are important to quantify the role of superdiffusive carriers in ultrafast energy transport, which is involved in different processes in solid state physics or femtochemistry.

© 2014 Optical Society of America

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  26. M. Hada, D. Zhang, A. Casandruc, R. J. D. Miller, Y. Hontani, J. Matsuo, R. E. Marvel, and R. F. Haglund, “Hot electron injection-driven phase transitions,” Phys. Rev. B 86, 134101 (2012).
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  29. M. Welkowsky and R. Braunstein, “Wavelength-modulated reflectivity of the noble metals,” Solid State Commun. 9, 2139–2142 (1971).
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  35. C. Thomsen, H. T. Grahn, H. J. Maris, and J. Tauc, “Surface generation and detection of phonons by picosecond light pulses,” Phys. Rev. B 34, 4129–4138 (1986).
    [CrossRef]
  36. B. Perrin, B. Bonello, J. C. Jeannet, and E. Romanet, “Interferometric detection of hypersound waves in modulated structures,” Prog. Nat. Sci. 6, 444–448 (1996).
  37. A. Devos and C. Lerouge, “Evidence of laser-wavelength effect in picosecond ultrasonics: possible connection with interband transitions,” Phys. Rev. Lett. 86, 2669–2672 (2001).
    [CrossRef]
  38. H.-N. Lin, R. J. Stoner, H. J. Maris, and J. Tauc, “Phonon attenuation and velocity measurements in transparent materials by picosecond acoustic interferometry,” J. Appl. Phys. 69, 3816–3822 (1991).
    [CrossRef]
  39. P. Babilotte, P. Ruello, D. Mounier, T. Pezeril, G. Vaudel, M. Edely, J.-M. Breteau, V. Gusev, and K. Blary, “Femtosecond laser generation and detection of high-frequency acoustic phonons in GaAs semiconductors,” Phys. Rev. B 81, 245207 (2010).
    [CrossRef]
  40. E. G. Every and A. A. Maznev, “Dispersion of an acoustic pulse passing through a large-grained polycrystalline film,” J. Acoust. Soc. Am. 131, 4491–4499 (2012).
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  41. V. Kanchana, G. Vaitheeswaran, A. Svane, and A. Delin, “First-principles study of elastic properties of CeO2, ThO2 and PoO2,” J. Phys. 18, 9615–9624 (2006).
    [CrossRef]
  42. O. B. Wright, “Thickness and sound velocity measurement in thin transparent films with laser picosecond acoustics,” J. Appl. Phys. 71, 1617–1627 (1992).
    [CrossRef]
  43. V. Gusev, “Laser hypersonics in fundamental and applied research,” Acustica 82, S37–S45 (1996).
  44. F.-C. Chiu and C.-M. Lai, “Optical and electrical characterizations of cerium oxide thin films,” J. Phys. D 43, 075104 (2010).
    [CrossRef]
  45. U. Gerhardts, “Effect of uniaxial and hydrostatic strain on the optical constants and the electronic structure of copper,” Phys. Rev. 172, 651–664 (1968).
    [CrossRef]
  46. K. J. Manke, A. A. Maznev, C. Klieber, V. Shalagatskyi, V. V. Temnov, D. Makarov, S.-H. Baek, C.-B. Eom, and K. A. Nelson, “Detection of shorter-than-skin-depth acoustic pulses in a metal film via transient reflectivity,” Appl. Phys. Lett. 103, 173104 (2013).
  47. S. Kaltenborn, Y.-H. Zhu, and H. C. Schneider, “Wave-diffusion theory of spin transport in metals after ultrashort-pulse excitation,” Phys. Rev. B 85, 235101 (2012).
    [CrossRef]
  48. V. E. Gusev, “On the duration of acoustic pulses excited by subpicosecond laser action on metals,” Opt. Commun. 94, 76–78 (1992).
    [CrossRef]
  49. A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
    [CrossRef]
  50. D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
    [CrossRef]

2013 (3)

V. V. Temnov, C. Klieber, K. A. Nelson, T. Thomay, V. Knittel, A. Leitenstorfer, D. Makarov, M. Albrecht, and R. Bratschitsch, “Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons,” Nat. Commun. 4, 1468–1477 (2013).
[CrossRef]

K. J. Manke, A. A. Maznev, C. Klieber, V. Shalagatskyi, V. V. Temnov, D. Makarov, S.-H. Baek, C.-B. Eom, and K. A. Nelson, “Detection of shorter-than-skin-depth acoustic pulses in a metal film via transient reflectivity,” Appl. Phys. Lett. 103, 173104 (2013).

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[CrossRef]

2012 (5)

D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
[CrossRef]

S. Kaltenborn, Y.-H. Zhu, and H. C. Schneider, “Wave-diffusion theory of spin transport in metals after ultrashort-pulse excitation,” Phys. Rev. B 85, 235101 (2012).
[CrossRef]

E. G. Every and A. A. Maznev, “Dispersion of an acoustic pulse passing through a large-grained polycrystalline film,” J. Acoust. Soc. Am. 131, 4491–4499 (2012).
[CrossRef]

V. V. Temnov, “Ultrafast acousto-magneto-plasmonics,” Nat. Photonics 6, 728–736 (2012).
[CrossRef]

M. Hada, D. Zhang, A. Casandruc, R. J. D. Miller, Y. Hontani, J. Matsuo, R. E. Marvel, and R. F. Haglund, “Hot electron injection-driven phase transitions,” Phys. Rev. B 86, 134101 (2012).
[CrossRef]

2011 (1)

A. Melnikov, I. Razdolski, T. O. Wehling, E. Th. Papaioannou, V. Roddatis, P. Fumagalli, O. Aktsipetrov, A. I. Lichtenstein, and U. Bovensiepen, “Ultrafast transport of laser-excited spin-polarized carriers in Au/Fe/MgO(001),” Phys. Rev. Lett. 107, 076601 (2011).
[CrossRef]

2010 (4)

M. Battiato, K. Carva, and P. M. Oppeneer, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” Phys. Rev. Lett. 105, 027203 (2010).
[CrossRef]

B. Koopmans, G. Malinowski, F. Dalla Longa, D. Steiauf, M. Fahnle, T. Roth, M. Cinchetti, and M. Aeschlimann, “Explaining the paradoxical diversity of ultrafast laser-induced demagnetization,” Nat. Mater. 9, 259–265 (2010).

P. Babilotte, P. Ruello, D. Mounier, T. Pezeril, G. Vaudel, M. Edely, J.-M. Breteau, V. Gusev, and K. Blary, “Femtosecond laser generation and detection of high-frequency acoustic phonons in GaAs semiconductors,” Phys. Rev. B 81, 245207 (2010).
[CrossRef]

F.-C. Chiu and C.-M. Lai, “Optical and electrical characterizations of cerium oxide thin films,” J. Phys. D 43, 075104 (2010).
[CrossRef]

2009 (1)

Y. Li, Q. Miao, A. V. Nurmikko, and H. J. Maris, “Picosecond ultrasonic measurements using an optical cavity,” J. Appl. Phys. 105, 083516 (2009).
[CrossRef]

2007 (1)

T. Pezeril, P. Ruello, S. Gougeon, N. Chigarev, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Generation and detection of plane coherent shear picosecond acoustic pulses by lasers: experiment and theory,” Phys. Rev. B 75, 174307 (2007).
[CrossRef]

2006 (2)

T. Pezeril, N. Chigarev, P. Ruello, S. Gougeon, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Laser acoustics with picosecond collimated shear strain beams in single crystals and polycrystalline materials,” Phys. Rev. B 73, 132301 (2006).
[CrossRef]

V. Kanchana, G. Vaitheeswaran, A. Svane, and A. Delin, “First-principles study of elastic properties of CeO2, ThO2 and PoO2,” J. Phys. 18, 9615–9624 (2006).
[CrossRef]

2003 (1)

T. Saito, O. Matsuda, and O. B. Wright, “Picosecond acoustic phonon pulse generation in nickel and chromium,” Phys. Rev. B 67, 205421 (2003).
[CrossRef]

2001 (1)

A. Devos and C. Lerouge, “Evidence of laser-wavelength effect in picosecond ultrasonics: possible connection with interband transitions,” Phys. Rev. Lett. 86, 2669–2672 (2001).
[CrossRef]

2000 (3)

J. W. Gadzuk, “Hot-electron femtochemistry at surfaces: on the role of multiple electron processes in desorption,” Chem. Phys. 251, 87–97 (2000).
[CrossRef]

J. Hohlfeld, S.-S. Wellershoff, J. Gudde, U. Conrad, V. Juhnka, and E. Matthias, “Electron and lattice dynamics following optical excitation of metals,” Chem. Phys. 251, 237–258 (2000).
[CrossRef]

N. Del Fatti, C. Voisin, M. Achermann, S. Tzortzakis, D. Christofilos, and F. Vallee, “Nonequilibrium electron dynamics in noble metals,” Phys. Rev. B 61, 16956–16966 (2000).
[CrossRef]

1998 (2)

N. Del Fatti, R. Bouffanais, F. Vallee, and C. Flytzanis, “Nonequilibrium electron interactions in metal films,” Phys. Rev. Lett. 81, 922–925 (1998).
[CrossRef]

V. E. Gusev and O. B. Wright, “Ultrafast nonequilibrium dynamics of electrons in metals,” Phys. Rev. B 57, 2878–2888 (1998).
[CrossRef]

1996 (2)

B. Perrin, B. Bonello, J. C. Jeannet, and E. Romanet, “Interferometric detection of hypersound waves in modulated structures,” Prog. Nat. Sci. 6, 444–448 (1996).

V. Gusev, “Laser hypersonics in fundamental and applied research,” Acustica 82, S37–S45 (1996).

1995 (1)

O. B. Wright and V. Gusev, “Ultrafast generation of acoustic waves in copper,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 42, 331–338 (1995).
[CrossRef]

1994 (2)

O. B. Wright, “Ultrafast nonequilibrium stress generation in gold and silver,” Phys. Rev. B 49, 9985–9988 (1994).
[CrossRef]

G. Tas and H. J. Maris, “Electron diffusion in metals studied by picosecond ultrasonics,” Phys. Rev. B 49, 15046–15054 (1994).
[CrossRef]

1993 (1)

T. Juhasz, H. E. Elsayed-Ali, G. O. Smith, C. Suarez, and W. E. Bron, “Direct measurements of the transport of nonequilibrium electrons in gold films with different crystal structures,” Phys. Rev. B 48, 15488–15491 (1993).
[CrossRef]

1992 (3)

H.-N. Lin, R. J. Stoner, H. J. Maris, J. M. E. Harper, J. C. Cabral, and J. H. W. Rubloff, “Nondestructive detection of titanium disilicide phase transformation by picosecond ultrasonics,” Appl. Phys. Lett. 61, 2700–2702 (1992).
[CrossRef]

O. B. Wright, “Thickness and sound velocity measurement in thin transparent films with laser picosecond acoustics,” J. Appl. Phys. 71, 1617–1627 (1992).
[CrossRef]

V. E. Gusev, “On the duration of acoustic pulses excited by subpicosecond laser action on metals,” Opt. Commun. 94, 76–78 (1992).
[CrossRef]

1991 (1)

H.-N. Lin, R. J. Stoner, H. J. Maris, and J. Tauc, “Phonon attenuation and velocity measurements in transparent materials by picosecond acoustic interferometry,” J. Appl. Phys. 69, 3816–3822 (1991).
[CrossRef]

1990 (1)

S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
[CrossRef]

1987 (4)

S. D. Brorson, J. G. Fujimoto, and E. P. Ippen, “Femtosecond electronic heat-transport dynamics in thin gold film,” Phys. Rev. Lett. 59, 1962–1965 (1987).
[CrossRef]

H. E. Elsayed-Ali, T. B. Norris, M. A. Pessot, and G. A. Mourou, “Time-resolved observation of electron–phonon relaxation in copper,” Phys. Rev. Lett. 58, 1212–1215 (1987).
[CrossRef]

R. W. Schoenlein, W. Z. Lin, J. G. Fujimoto, and G. L. Eesley, “Femtosecond studies of nonequilibrium electronic processes in metals,” Phys. Rev. Lett. 58, 1680–1683 (1987).
[CrossRef]

P. B. Allen, “Theory of thermal relaxation of electrons in metals,” Phys. Rev. Lett. 59, 1460–1463 (1987).
[CrossRef]

1986 (2)

C. Thomsen, H. T. Grahn, H. J. Maris, and J. Tauc, “Surface generation and detection of phonons by picosecond light pulses,” Phys. Rev. B 34, 4129–4138 (1986).
[CrossRef]

G. L. Eesley, “Generation of nonequilibrium electron and lattice temperatures in copper by picosecond laser pulses,” Phys. Rev. B 33, 2144–2151 (1986).
[CrossRef]

1975 (1)

O. Jepsen, “Electronic structure and magnetic breakdown in titanium,” Phys. Rev. B 12, 2988–2997 (1975).
[CrossRef]

1971 (1)

M. Welkowsky and R. Braunstein, “Wavelength-modulated reflectivity of the noble metals,” Solid State Commun. 9, 2139–2142 (1971).
[CrossRef]

1968 (1)

U. Gerhardts, “Effect of uniaxial and hydrostatic strain on the optical constants and the electronic structure of copper,” Phys. Rev. 172, 651–664 (1968).
[CrossRef]

1962 (2)

H. Ehrenreich and H. R. Philipp, “Optical properties of Ag and Cu,” Phys. Rev. 128, 1622–1629 (1962).
[CrossRef]

C. R. Crowell, W. G. Spitzer, L. E. Howarth, and E. E. LaBate, “Attenuation length measurements of hot electrons in metal films,” Phys. Rev. 127, 2006–2015 (1962).
[CrossRef]

Achermann, M.

N. Del Fatti, C. Voisin, M. Achermann, S. Tzortzakis, D. Christofilos, and F. Vallee, “Nonequilibrium electron dynamics in noble metals,” Phys. Rev. B 61, 16956–16966 (2000).
[CrossRef]

Adam, R.

D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
[CrossRef]

Aeschlimann, M.

D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
[CrossRef]

B. Koopmans, G. Malinowski, F. Dalla Longa, D. Steiauf, M. Fahnle, T. Roth, M. Cinchetti, and M. Aeschlimann, “Explaining the paradoxical diversity of ultrafast laser-induced demagnetization,” Nat. Mater. 9, 259–265 (2010).

Aktsipetrov, O.

A. Melnikov, I. Razdolski, T. O. Wehling, E. Th. Papaioannou, V. Roddatis, P. Fumagalli, O. Aktsipetrov, A. I. Lichtenstein, and U. Bovensiepen, “Ultrafast transport of laser-excited spin-polarized carriers in Au/Fe/MgO(001),” Phys. Rev. Lett. 107, 076601 (2011).
[CrossRef]

Albrecht, M.

V. V. Temnov, C. Klieber, K. A. Nelson, T. Thomay, V. Knittel, A. Leitenstorfer, D. Makarov, M. Albrecht, and R. Bratschitsch, “Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons,” Nat. Commun. 4, 1468–1477 (2013).
[CrossRef]

Allen, P. B.

P. B. Allen, “Theory of thermal relaxation of electrons in metals,” Phys. Rev. Lett. 59, 1460–1463 (1987).
[CrossRef]

Anderson, O. L.

O. L. Anderson, “Determination and some uses of isotropic elastic constants of polycrystalline aggregates using single-crystal data,” in Physical Acoustics, W. P. Mason, ed. (Academic, 1965).

Aschroft, N. W.

N. W. Aschroft and N. D. Mermin, Solid State Physics (Saunders College, 1976).

Babilotte, P.

P. Babilotte, P. Ruello, D. Mounier, T. Pezeril, G. Vaudel, M. Edely, J.-M. Breteau, V. Gusev, and K. Blary, “Femtosecond laser generation and detection of high-frequency acoustic phonons in GaAs semiconductors,” Phys. Rev. B 81, 245207 (2010).
[CrossRef]

Baek, S.-H.

K. J. Manke, A. A. Maznev, C. Klieber, V. Shalagatskyi, V. V. Temnov, D. Makarov, S.-H. Baek, C.-B. Eom, and K. A. Nelson, “Detection of shorter-than-skin-depth acoustic pulses in a metal film via transient reflectivity,” Appl. Phys. Lett. 103, 173104 (2013).

Battiato, M.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[CrossRef]

D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
[CrossRef]

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A. Melnikov, I. Razdolski, T. O. Wehling, E. Th. Papaioannou, V. Roddatis, P. Fumagalli, O. Aktsipetrov, A. I. Lichtenstein, and U. Bovensiepen, “Ultrafast transport of laser-excited spin-polarized carriers in Au/Fe/MgO(001),” Phys. Rev. Lett. 107, 076601 (2011).
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V. V. Temnov, C. Klieber, K. A. Nelson, T. Thomay, V. Knittel, A. Leitenstorfer, D. Makarov, M. Albrecht, and R. Bratschitsch, “Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons,” Nat. Commun. 4, 1468–1477 (2013).
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[CrossRef]

T. Pezeril, P. Ruello, S. Gougeon, N. Chigarev, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Generation and detection of plane coherent shear picosecond acoustic pulses by lasers: experiment and theory,” Phys. Rev. B 75, 174307 (2007).
[CrossRef]

T. Pezeril, N. Chigarev, P. Ruello, S. Gougeon, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Laser acoustics with picosecond collimated shear strain beams in single crystals and polycrystalline materials,” Phys. Rev. B 73, 132301 (2006).
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T. Juhasz, H. E. Elsayed-Ali, G. O. Smith, C. Suarez, and W. E. Bron, “Direct measurements of the transport of nonequilibrium electrons in gold films with different crystal structures,” Phys. Rev. B 48, 15488–15491 (1993).
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S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
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H.-N. Lin, R. J. Stoner, H. J. Maris, J. M. E. Harper, J. C. Cabral, and J. H. W. Rubloff, “Nondestructive detection of titanium disilicide phase transformation by picosecond ultrasonics,” Appl. Phys. Lett. 61, 2700–2702 (1992).
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M. Battiato, K. Carva, and P. M. Oppeneer, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” Phys. Rev. Lett. 105, 027203 (2010).
[CrossRef]

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M. Hada, D. Zhang, A. Casandruc, R. J. D. Miller, Y. Hontani, J. Matsuo, R. E. Marvel, and R. F. Haglund, “Hot electron injection-driven phase transitions,” Phys. Rev. B 86, 134101 (2012).
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S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
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T. Pezeril, P. Ruello, S. Gougeon, N. Chigarev, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Generation and detection of plane coherent shear picosecond acoustic pulses by lasers: experiment and theory,” Phys. Rev. B 75, 174307 (2007).
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T. Pezeril, N. Chigarev, P. Ruello, S. Gougeon, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Laser acoustics with picosecond collimated shear strain beams in single crystals and polycrystalline materials,” Phys. Rev. B 73, 132301 (2006).
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J. Hohlfeld, S.-S. Wellershoff, J. Gudde, U. Conrad, V. Juhnka, and E. Matthias, “Electron and lattice dynamics following optical excitation of metals,” Chem. Phys. 251, 237–258 (2000).
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C. R. Crowell, W. G. Spitzer, L. E. Howarth, and E. E. LaBate, “Attenuation length measurements of hot electrons in metal films,” Phys. Rev. 127, 2006–2015 (1962).
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B. Koopmans, G. Malinowski, F. Dalla Longa, D. Steiauf, M. Fahnle, T. Roth, M. Cinchetti, and M. Aeschlimann, “Explaining the paradoxical diversity of ultrafast laser-induced demagnetization,” Nat. Mater. 9, 259–265 (2010).

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V. Kanchana, G. Vaitheeswaran, A. Svane, and A. Delin, “First-principles study of elastic properties of CeO2, ThO2 and PoO2,” J. Phys. 18, 9615–9624 (2006).
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A. Devos and C. Lerouge, “Evidence of laser-wavelength effect in picosecond ultrasonics: possible connection with interband transitions,” Phys. Rev. Lett. 86, 2669–2672 (2001).
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S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
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S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
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P. Babilotte, P. Ruello, D. Mounier, T. Pezeril, G. Vaudel, M. Edely, J.-M. Breteau, V. Gusev, and K. Blary, “Femtosecond laser generation and detection of high-frequency acoustic phonons in GaAs semiconductors,” Phys. Rev. B 81, 245207 (2010).
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R. W. Schoenlein, W. Z. Lin, J. G. Fujimoto, and G. L. Eesley, “Femtosecond studies of nonequilibrium electronic processes in metals,” Phys. Rev. Lett. 58, 1680–1683 (1987).
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A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
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S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
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B. Koopmans, G. Malinowski, F. Dalla Longa, D. Steiauf, M. Fahnle, T. Roth, M. Cinchetti, and M. Aeschlimann, “Explaining the paradoxical diversity of ultrafast laser-induced demagnetization,” Nat. Mater. 9, 259–265 (2010).

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A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
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N. Del Fatti, R. Bouffanais, F. Vallee, and C. Flytzanis, “Nonequilibrium electron interactions in metal films,” Phys. Rev. Lett. 81, 922–925 (1998).
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R. W. Schoenlein, W. Z. Lin, J. G. Fujimoto, and G. L. Eesley, “Femtosecond studies of nonequilibrium electronic processes in metals,” Phys. Rev. Lett. 58, 1680–1683 (1987).
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S. D. Brorson, J. G. Fujimoto, and E. P. Ippen, “Femtosecond electronic heat-transport dynamics in thin gold film,” Phys. Rev. Lett. 59, 1962–1965 (1987).
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A. Melnikov, I. Razdolski, T. O. Wehling, E. Th. Papaioannou, V. Roddatis, P. Fumagalli, O. Aktsipetrov, A. I. Lichtenstein, and U. Bovensiepen, “Ultrafast transport of laser-excited spin-polarized carriers in Au/Fe/MgO(001),” Phys. Rev. Lett. 107, 076601 (2011).
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T. Pezeril, N. Chigarev, P. Ruello, S. Gougeon, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Laser acoustics with picosecond collimated shear strain beams in single crystals and polycrystalline materials,” Phys. Rev. B 73, 132301 (2006).
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J. Hohlfeld, S.-S. Wellershoff, J. Gudde, U. Conrad, V. Juhnka, and E. Matthias, “Electron and lattice dynamics following optical excitation of metals,” Chem. Phys. 251, 237–258 (2000).
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P. Babilotte, P. Ruello, D. Mounier, T. Pezeril, G. Vaudel, M. Edely, J.-M. Breteau, V. Gusev, and K. Blary, “Femtosecond laser generation and detection of high-frequency acoustic phonons in GaAs semiconductors,” Phys. Rev. B 81, 245207 (2010).
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T. Pezeril, P. Ruello, S. Gougeon, N. Chigarev, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Generation and detection of plane coherent shear picosecond acoustic pulses by lasers: experiment and theory,” Phys. Rev. B 75, 174307 (2007).
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T. Pezeril, N. Chigarev, P. Ruello, S. Gougeon, D. Mounier, J.-M. Breteau, P. Picart, and V. Gusev, “Laser acoustics with picosecond collimated shear strain beams in single crystals and polycrystalline materials,” Phys. Rev. B 73, 132301 (2006).
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M. Hada, D. Zhang, A. Casandruc, R. J. D. Miller, Y. Hontani, J. Matsuo, R. E. Marvel, and R. F. Haglund, “Hot electron injection-driven phase transitions,” Phys. Rev. B 86, 134101 (2012).
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H.-N. Lin, R. J. Stoner, H. J. Maris, J. M. E. Harper, J. C. Cabral, and J. H. W. Rubloff, “Nondestructive detection of titanium disilicide phase transformation by picosecond ultrasonics,” Appl. Phys. Lett. 61, 2700–2702 (1992).
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J. Hohlfeld, S.-S. Wellershoff, J. Gudde, U. Conrad, V. Juhnka, and E. Matthias, “Electron and lattice dynamics following optical excitation of metals,” Chem. Phys. 251, 237–258 (2000).
[CrossRef]

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A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
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M. Hada, D. Zhang, A. Casandruc, R. J. D. Miller, Y. Hontani, J. Matsuo, R. E. Marvel, and R. F. Haglund, “Hot electron injection-driven phase transitions,” Phys. Rev. B 86, 134101 (2012).
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C. R. Crowell, W. G. Spitzer, L. E. Howarth, and E. E. LaBate, “Attenuation length measurements of hot electrons in metal films,” Phys. Rev. 127, 2006–2015 (1962).
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Ippen, E. P.

S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
[CrossRef]

S. D. Brorson, J. G. Fujimoto, and E. P. Ippen, “Femtosecond electronic heat-transport dynamics in thin gold film,” Phys. Rev. Lett. 59, 1962–1965 (1987).
[CrossRef]

Jeannet, J. C.

B. Perrin, B. Bonello, J. C. Jeannet, and E. Romanet, “Interferometric detection of hypersound waves in modulated structures,” Prog. Nat. Sci. 6, 444–448 (1996).

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O. Jepsen, “Electronic structure and magnetic breakdown in titanium,” Phys. Rev. B 12, 2988–2997 (1975).
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T. Juhasz, H. E. Elsayed-Ali, G. O. Smith, C. Suarez, and W. E. Bron, “Direct measurements of the transport of nonequilibrium electrons in gold films with different crystal structures,” Phys. Rev. B 48, 15488–15491 (1993).
[CrossRef]

Juhnka, V.

J. Hohlfeld, S.-S. Wellershoff, J. Gudde, U. Conrad, V. Juhnka, and E. Matthias, “Electron and lattice dynamics following optical excitation of metals,” Chem. Phys. 251, 237–258 (2000).
[CrossRef]

Kachel, T.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
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V. Kanchana, G. Vaitheeswaran, A. Svane, and A. Delin, “First-principles study of elastic properties of CeO2, ThO2 and PoO2,” J. Phys. 18, 9615–9624 (2006).
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Kapteyn, H. C.

D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
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V. Gusev and A. Karabutov, Laser Optoacoustics (AIP, 1993).

Kazeroonian, A.

S. D. Brorson, A. Kazeroonian, J. S. Moodera, D. W. Face, T. K. Cheng, E. P. Ippen, M. S. Dresselhaus, and G. Dresselhaus, “Femtosecond room-temperature measurement of the electron–phonon coupling constant λ in metallic superconductors,” Phys. Rev. Lett. 64, 2172–2175 (1990).
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K. J. Manke, A. A. Maznev, C. Klieber, V. Shalagatskyi, V. V. Temnov, D. Makarov, S.-H. Baek, C.-B. Eom, and K. A. Nelson, “Detection of shorter-than-skin-depth acoustic pulses in a metal film via transient reflectivity,” Appl. Phys. Lett. 103, 173104 (2013).

V. V. Temnov, C. Klieber, K. A. Nelson, T. Thomay, V. Knittel, A. Leitenstorfer, D. Makarov, M. Albrecht, and R. Bratschitsch, “Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons,” Nat. Commun. 4, 1468–1477 (2013).
[CrossRef]

Knittel, V.

V. V. Temnov, C. Klieber, K. A. Nelson, T. Thomay, V. Knittel, A. Leitenstorfer, D. Makarov, M. Albrecht, and R. Bratschitsch, “Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons,” Nat. Commun. 4, 1468–1477 (2013).
[CrossRef]

Koopmans, B.

B. Koopmans, G. Malinowski, F. Dalla Longa, D. Steiauf, M. Fahnle, T. Roth, M. Cinchetti, and M. Aeschlimann, “Explaining the paradoxical diversity of ultrafast laser-induced demagnetization,” Nat. Mater. 9, 259–265 (2010).

LaBate, E. E.

C. R. Crowell, W. G. Spitzer, L. E. Howarth, and E. E. LaBate, “Attenuation length measurements of hot electrons in metal films,” Phys. Rev. 127, 2006–2015 (1962).
[CrossRef]

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F.-C. Chiu and C.-M. Lai, “Optical and electrical characterizations of cerium oxide thin films,” J. Phys. D 43, 075104 (2010).
[CrossRef]

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D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
[CrossRef]

Leitenstorfer, A.

V. V. Temnov, C. Klieber, K. A. Nelson, T. Thomay, V. Knittel, A. Leitenstorfer, D. Makarov, M. Albrecht, and R. Bratschitsch, “Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons,” Nat. Commun. 4, 1468–1477 (2013).
[CrossRef]

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A. Devos and C. Lerouge, “Evidence of laser-wavelength effect in picosecond ultrasonics: possible connection with interband transitions,” Phys. Rev. Lett. 86, 2669–2672 (2001).
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Y. Li, Q. Miao, A. V. Nurmikko, and H. J. Maris, “Picosecond ultrasonic measurements using an optical cavity,” J. Appl. Phys. 105, 083516 (2009).
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H.-N. Lin, R. J. Stoner, H. J. Maris, J. M. E. Harper, J. C. Cabral, and J. H. W. Rubloff, “Nondestructive detection of titanium disilicide phase transformation by picosecond ultrasonics,” Appl. Phys. Lett. 61, 2700–2702 (1992).
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H.-N. Lin, R. J. Stoner, H. J. Maris, J. M. E. Harper, J. C. Cabral, and J. H. W. Rubloff, “Nondestructive detection of titanium disilicide phase transformation by picosecond ultrasonics,” Appl. Phys. Lett. 61, 2700–2702 (1992).
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D. Rudolf, C. La-O-Vorakiat, M. Battiato, R. Adam, J. M. Shaw, E. Turgut, P. Maldonado, S. Mathias, P. Grychtol, H. T. Nembach, T. J. Silva, M. Aeschlimann, H. C. Kapteyn, M. M. Murnane, C. M. Schneider, and P. M. Oppeneer, “Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current,” Nat. Commun. 3, 1037–1043 (2012).
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H.-N. Lin, R. J. Stoner, H. J. Maris, J. M. E. Harper, J. C. Cabral, and J. H. W. Rubloff, “Nondestructive detection of titanium disilicide phase transformation by picosecond ultrasonics,” Appl. Phys. Lett. 61, 2700–2702 (1992).
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Figures (5)

Fig. 1.
Fig. 1.

Femtosecond laser light is absorbed over the skin depth region (absorption profile depicted by a solid red line) while superdiffusive hot electrons transport energy up to the copper/titanium interface (profile depicted in dashed line). Through the electron–phonon coupling process, coherent acoustic phonons are generated not only at the copper surface (z0), but also at the copper/titanium interface (zH).

Fig. 2.
Fig. 2.

(a) Description of the three different front–back and front–front experimental configurations. The optical excitation is depicted as red lines and indicate the evanescent light penetration in the metals (copper or titanium). The dashed lines depict the energy distribution of the excited hot electrons, consecutively to their superdiffusive transport. (b) Time-resolved optical reflectivity measurements according to the three configurations (1, 2, and 3). The time constant τCu=H/VCu corresponds to the time of flight of the acoustic wave packet through the copper layer of thickness H at the acoustic speed VCu. B, and F refers to coherent acoustic phonons emitted from the back and the front, respectively.

Fig. 3.
Fig. 3.

(a) Sketch of the electronic density of states in copper. When electrons are excited, it gives rise to a smearing of the Fermi distribution. At a given position inside a metal, this excitation can be mediated either by direct optical excitation or by hot carrier transport toward this position. Probing the smearing of the Fermi distribution at different wavelengths leads to different optical responses. (b) Effect of the probe wavelength on the time resolved optical reflectivity obtained according to configuration 3 (front–front). Probing the hot electron distribution with a probe photon energy larger or smaller than EF-Ed, leads to an increase or decrease of the onset of the transient optical reflectivity. (c) Probe wavelength dependence of the transient optical reflectivity obtained according to configuration 1 (back–front). The electronic response at t0ps exhibits a huge wavelength dependence, in accordance with theory.

Fig. 4.
Fig. 4.

Simulation of the first acoustic echo detected in configuration 1 (back–front) at τ=20ps [see Fig. 2(b)]. (a) Profile of the short acoustic strain emitted from the photo-excited titanium layer and propagating toward the protecting layer/copper surface, where it is detected. (b) Calculated (blue curve) and experimental (green curve) transient reflectivity signals for configuration 1, corresponding to the first acoustic echo. The dashed blue curve corresponds to the signal obtained if we do not take into account the transit time into the coating layer (i.e., h=0nm).

Fig. 5.
Fig. 5.

(a) Profiles of acoustic strains employed for simulating the B and F pulses for configuration 3 (front–front). Profile 1 accounts for the F pulse. The other acoustic pulse strain profiles are proposals for describing the B pulse (see discussion in the text). The continuous dashed black lines indicate the strain equal to zero. The curves have been shifted along the vertical and horizontal axes for clarity. (b) Calculated transient reflectivity signal associated with each acoustic strain profile. All curves have been shifted along the vertical axis for clarity.

Tables (1)

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Table 1. Some Physical Properties of Copper and Titanium

Equations (3)

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Δr/r=2ik0u(0)+C[(k1+k1η)0hη(z,t)dz+12k1η0hη(z,t)[r12e2ik1(hz)+1r12e2ik1(hz)]dz+12k2η(1r12r12)hη(z,t)e2ik2(zh)dz],
C=2ir12(1r012)(r01eik1h+r12eik1h)(eik1h+r01r12eik1h),
rij=ninjni+nj.

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