ChemRxiv
These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
Flannigan_CAP CDW Coupling_Combined.pdf (1.83 MB)

Coherent Phonon Disruption and Lock-In During a Photoinduced Charge-Density-Wave Phase Transition

preprint
submitted on 01.04.2021, 23:03 and posted on 05.04.2021, 04:34 by Spencer A. Reisbick, Yichao Zhang, Jialiang Chen, Paige Engen, David Flannigan
Ultrafast manipulation of phases and phase domains in quantum materials is a key approach to unraveling and harnessing interwoven effects of charge and lattice degrees of freedom. In the intensely-studied charge-density-wave (CDW) material, 1T-TaS2, phonon coupling to periodic lattice distortions (PLDs) and atomically-incoherent picosecond structural phase transitions suggest transitional periods could exist for delayed onset of mode coherence. Here we find evidence for such a connection between displacively-excited coherent acoustic phonons and PLDs using 4D ultrafast electron microscopy. Following femtosecond optical excitation of an ultrathin crystal, a propagating hybridized mode is imaged emerging from linear defects within a 1-μm region. Partial coherence and low amplitudes during onset of the incommensurate phase convert to higher-amplitude, increasingly-coherent oscillations as phase-growth stabilizes. The hybrid mode consists of large out-of-plane distortions coupled to basal-plane bond oscillations propagating at anomalously high velocities. The strongly-correlated behaviors observed here represent a potential means to control phase behaviors in quantum materials using defect-engineered coherent-phonon seeding.

Funding

DMR-1654318

DMR-2011401

American Chemical Society Petroleum Research Fund

DE-SC-0016371

Louise T. Dosdall Fellowship

History

Email Address of Submitting Author

flan0076@umn.edu

Institution

University of Minnesota

Country

USA

ORCID For Submitting Author

0000-0002-1829-1868

Declaration of Conflict of Interest

The authors declare no competing financial interest.

Exports