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Ultrafast manipulation of phase domains in quantum materials is a promising approach to unraveling and harnessing interwoven charge and lattice degrees of freedom. Here we find evidence for coupling of displacively excited coherent acoustic phonons (CAPs) and periodic lattice distortions (PLDs) in the intensely studied charge-density-wave material, 1T-TaS2, using 4D ultrafast electron microscopy (UEM). Initial photoinduced Bragg-peak dynamics reveal partial CAP coherence and localized c-axis dilations. Weak, partially coherent dynamics give way to higher-amplitude, increasingly coherent oscillations, the transition period of which matches that of photoinduced incommensurate domain growth and stabilization from the nearly-commensurate phase. With UEM imaging, it is found that phonon wave trains emerge from linear defects 100 ps after photoexcitation. The CAPs consist of coupled longitudinal and transverse character and propagate at anomalously high velocities along wave vectors independent from PLDs, instead being dictated by defect orientation. Such behaviors illustrate a means to control phases in quantum materials using defect-engineered coherent-phonon seeding.
Bibliographical noteFunding Information:
This material is based upon work supported by the National Science Foundation under Grant No. DMR-1654318. This work was partially supported by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-2011401. Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC program under Award Number DMR-2011401. J.C. was supported in part by the U.S. Department of Energy through the UMN Center for Quantum Materials under Grant No. DE-SC-0016371. Y.Z. acknowledges support from the Louise T. Dosdall Fellowship.
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PubMed: MeSH publication types
- Journal Article