期刊
PHYSICAL REVIEW MATERIALS
卷 1, 期 6, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevMaterials.1.060601
关键词
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资金
- US Department of Energy (DOE), Basic Energy Sciences, Materials Sciences and Engineering Division
- Department of Energy [DE-SC0012375]
- US DOE, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
- Office of Science of the US DOE [DE-AC02-05CH11231]
- DOE, Basic Energy Sciences, Materials Science and Engineering [DE-AC02-76SF00515]
- US DOE Office of Science Basic Energy Sciences [DE-FG02-04ER46147]
- Army Research Office [W911NF-14-1-0104]
Nanoscale phonon transport is a key process that governs thermal conduction in a wide range of materials and devices. Creating controlled phonon populations by resonant excitation at terahertz (THz) frequencies can drastically change the characteristics of nanoscale thermal transport and allow a direct real-space characterization of phonon mean-free paths. Using metamaterial-enhanced terahertz excitation, we tailored a phononic excitation by selectively populating low-frequency phonons within a nanoscale volume in a ferroelectric BaTiO3 thin film. Real-space time-resolved x-ray diffraction microscopy following THz excitation reveals ballistic phonon transport over a distance of hundreds of nm, two orders of magnitude longer than the averaged phonon mean-free path in BaTiO3. On longer length scales, diffusive phonon transport dominates the recovery of the transient strain response, largely due to heat conduction into the substrate. The measured real-space phonon transport can be directly compared with the phonon mean-free path as predicted by molecular dynamics modeling. This time-resolved real-space visualization of THz-matter interactions opens up opportunities to engineer and image nanoscale transient structural states with new functionalities.
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