Structural imaging of nanoscale phonon transport in ferroelectrics excited by metamaterial-enhanced terahertz fields

Yi Zhu, Frank Chen, Joonkyu Park, Kiran Sasikumar, Bin Hu, Anoop R. Damodaran, Il Woong Jung, Matthew J. Highland, Zhonghou Cai, I. Cheng Tung, Donald A. Walko, John W. Freeland, Lane W. Martin, Subramanian K.R.S. Sankaranarayanan, Paul G. Evans, Aaron M. Lindenberg, Haidan Wen

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

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.

Original languageEnglish (US)
Article number060601
JournalPhysical Review Materials
Volume1
Issue number6
DOIs
StatePublished - Nov 16 2017
Externally publishedYes

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