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Published April 15, 2014 | Erratum + Supplemental Material + Published
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Observing (non)linear lattice dynamics in graphite by ultrafast Kikuchi diffraction


In materials, the nature of the strain–stress relationship, which is fundamental to their properties, is determined by both the linear and nonlinear elastic responses. Whereas the linear response can be measured by various techniques, the nonlinear behavior is nontrivial to probe and to reveal its nature. Here, we report the methodology of time-resolved Kikuchi diffraction for mapping the (non)linear elastic response of nanoscale graphite following an ultrafast, impulsive strain excitation. It is found that the longitudinal wave propagating along the c-axis exhibits echoes with a frequency of 9.1 GHz, which indicates the reflections of strain between the two surfaces of the material with a speed of ∼4 km/s. Because Kikuchi diffraction enables the probing of strain in the transverse direction, we also observed a higher-frequency mode at 75.5 GHz, which has a relatively long lifetime, on the order of milliseconds. The fluence dependence and the polarization properties of this nonlinear mode are entirely different from those of the linear, longitudinal mode, and here we suggest a localized breather motion in the a-b plane as the origin of the nonlinear shear dynamics. The approach presented in this contribution has the potential for a wide range of applications because most crystalline materials exhibit Kikuchi diffraction.

Additional Information

© 2014 National Academy of Sciences. Contributed by Ahmed H. Zewail, March 5, 2014 (sent for review February 18, 2014). Published online before print March 31, 2014. We thank Dr. Sascha Schäfer for his contribution to the sample preparation and Dr. Aycan Yurtsever for his help in the measurements involving electron energy-loss spectroscopy. This work was supported by the National Science Foundation (Grant 0964886) and the Air Force Office of Scientific Research (Grant FA9550-10-1-0380). The Center for Physical Biology at the California Institute of Technology is supported by the Gordon and Betty Moore Foundation (Grant 695). W.L., G.M.V., and A.H.Z. contributed equally to this work. Author contributions: W.L., G.M.V., and A.H.Z. wrote the paper. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1404101111/-/DCSupplemental.


Correction for Liang et al., Observing (non)linear lattice dynamics in graphite by ultrafast Kikuchi diffraction PNAS 2015 112 (50) E7030; published ahead of print December 7, 2015, doi:10.1073/pnas.1522407112

Attached Files

Published - PNAS-2014-Liang-5491-6.pdf

Supplemental Material - pnas.201404101SI.pdf

Erratum - PNAS-2015--E7030.pdf


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