Control of two-phonon correlations and the mechanism of high-wavevector phonon generation by ultrafast light pulses
| Autor: | M. Chollet, James M. Glownia, Thomas Henighan, Jesse N. Clark, Diling Zhu, Mariano Trigo, David A. Reis, Michael Kozina, Sanghoon Song, Stephen Fahy, Mason Jiang, Hanzhe Liu |
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| Rok vydání: | 2016 |
| Předmět: |
Physics
Condensed matter physics Phonon 02 engineering and technology Expectation value 021001 nanoscience & nanotechnology 01 natural sciences Brillouin zone 0103 physical sciences Coherent states Wave vector 010306 general physics 0210 nano-technology Ultrashort pulse Excitation Squeezed coherent state |
| Zdroj: | Physical Review B. 94 |
| ISSN: | 2469-9969 2469-9950 |
| Popis: | Impulsive optical excitation can generate both coherent and squeezed phonons through first- and second-order Raman-like processes. The expectation value of the phonon displacement $\ensuremath{\langle}{u}_{q}\ensuremath{\rangle}$ oscillates at the phonon mode frequency for the coherent state but remains zero for a pure squeezed state. In contrast, both show oscillations in $\ensuremath{\langle}|{u}_{q}{|}^{2}\ensuremath{\rangle}$ at twice the phonon mode frequency. Therefore it can be difficult to distinguish them in a second-order measurement of the displacements as is typical in x-ray diffuse scattering. Here we demonstrate a simple method to distinguish the generation mechanism by measurement of the diffuse scattering following double-impulsive excitation. We find in the case of Ge and GaAs that the generation of large wavevector phonons spanning the Brillouin zone is dominated by a second-order process. |
| Databáze: | OpenAIRE |
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