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Conference papers

Coherent acoustic phonon generation with THz and Near-IR pulsed radiation in metals and topological insulators nanofilms

Abstract : During the last decade, time-domain THz spectroscopy and imaging became widely used techniques in various fields of physics, chemistry, and biology. Advancements in THz generation techniques<sup>[1]</sup> have opened new perspectives in solid-state physics and material science: THz pulsed radiation can now be used to probe to drive at the picosecond time scale different degrees of freedom of a solid<sup>[2]</sup>. <par>Non-destructive THz remote sensing and control of a solid are now one of the widely discussed topics in the scientific community. For example, the excitation of antiferromagnon and optical phonons with pulsed THz radiation were recently reported. In the meantime, no clear explanation<sup>[3]</sup> of a coherent acoustic phonon (CAP) generation process with THz radiation exists so far, while CAP driven by visible or near-infrared (NIR) light are well studied<sup>[4]</sup>. In that regard, a back-to-back study of NIR and THz ultrafast dynamics in a set of ?simple? materials should help to understand the physics behind the CAP excitation mechanism with intense THz pulsed radiation. <par>We performed the pump-probe measurements with a sub-picosecond time resolution on the PVD deposited nm-thin Cr and Al films and on a set of Bi<sub>2</sub>Te<sub>3</sub> MBE grown topological insulators. Studied materials were irradiated with femtosecond pulses with a central wavelength of 800 nm (375 THz/1.54 eV) or 600 �m (0.5 THz/2 meV) and probed at 400 nm (749.5 THz/3.1 eV). A direct comparison between THz and NIR excitation complemented by THz-TDS and FDTD simulations shows that the mechanism of CAP excitation with THz is similar to NIR, and linked to the well-known thermoelastic process. <par><b>Refferences</b> <par>[1] H.Hirori et al., Appl. Phys. Lett. 98, 091106 (2011). <par>[2] T. Kampfrath et al., Nat. Photonics 7, 680 (2013). <par>[3] J.M. Manceau, et al., Appl. Phys. Lett. 97, (2010). <par>[4] P. Ruello and V.E. Gusev, Ultrasonics 56, 21 (2015).
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Artem Levchuk, Gwenäelle Vaudel, Bartosz Wilk, Francois Labbé, Katarzyna Balin, et al.. Coherent acoustic phonon generation with THz and Near-IR pulsed radiation in metals and topological insulators nanofilms. Forum Acusticum, Dec 2020, Lyon, France. pp.1815-1815, ⟨10.48465/fa.2020.0168⟩. ⟨hal-03240230⟩



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