Generation mechanism of terahertz coherent acoustic phonons in Fe
2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 22, 220301Article in journal (Refereed) PublishedText
We use femtosecond time-resolved hard x-ray scattering to detect coherent acoustic phonons generated during ultrafast laser excitation of ferromagnetic bcc Fe films grown on MgO(001). We observe the coherent longitudinal-acoustic phonons as a function of wave vector through analysis of the temporal oscillations in the x-ray scattering signal. The width of the extracted strain wave front associated with this coherent motion is similar to 100 fs. An effective electronic Gruneisen parameter is extracted within a two-temperature model. However, ab initio calculations show that the phonons are nonthermal on the time scale of the experiment, which calls into question the validity of extracting physical constants by fitting such a two-temperature model.
Place, publisher, year, edition, pages
2016. Vol. 93, no 22, 220301
Condensed Matter Physics
IdentifiersURN: urn:nbn:se:uu:diva-299038DOI: 10.1103/PhysRevB.93.220301ISI: 000377498000001OAI: oai:DiVA.org:uu-299038DiVA: diva2:948810
FunderEU, European Research Council, 281043Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)Knut and Alice Wallenberg Foundation