Generation of coherent phonons in bismuth by ultrashort laser pulses in the visible and NIR: Displacive versus impulsive excitation mechanism |
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Authors: | AA Melnikov OV MisochkoSV Chekalin |
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Institution: | a Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow region, Russia b Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Moscow region, Russia c Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow region, Russia |
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Abstract: | We have applied femtosecond pump-probe technique with variable pump wavelength to study coherent lattice dynamics in Bi single crystal. Comparison of the coherent amplitude as a function of pump photon energy for two different in symmetry Eg and A1g phonon modes with respective spontaneous resonance Raman profiles reveals that their generation mechanisms are quite distinct. We show that displacive excitation, which is the main mechanism for the generation of coherent A1g phonons, cannot be reduced to the Raman scattering responsible for the generation of lower symmetry coherent lattice modes. |
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