Projects per year
Precise manipulation and control of coherent lattice oscillations via nanostructuring and phonon-wave interference has the potential to significantly impact a broad array of technologies and research areas. Resolving the dynamics of individual phonons in defect-laden materials presents an enormous challenge, however, owing to the interdependent nanoscale and ultrafast spatiotemporal scales. Here we report direct, real-space imaging of the emergence and evolution of acoustic phonons at individual defects in crystalline WSe 2 and Ge. Via bright-field imaging with an ultrafast electron microscope, we are able to image the sub-picosecond nucleation and the launch of wavefronts at step edges and resolve dispersion behaviours during propagation and scattering. We discover that the appearance of speed-of-sound (for example, 6 nm ps-1) wavefronts are influenced by spatially varying nanoscale strain fields, taking on the appearance of static bend contours during propagation. These observations provide unprecedented insight into the roles played by individual atomic and nanoscale features on acoustic-phonon dynamics.
Bibliographical noteFunding Information:
This work was supported primarily by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-1420013, in part by a 3M Nontenured Faculty Award under Award Number 13673369, and in part by the Arnold and Mabel Beckman Foundation through a 2015 Beckman Young Investigator Award. D.A.P. acknowledges support from a Doctoral Dissertation Fellowship received from the Graduate School at the University of Minnesota. Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research under Award Number 53116-DNI7.
How much support was provided by MRSEC?
Reporting period for MRSEC
- Period 3
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't