Ultrafast X-Ray Scattering Reveals Composite Amplitude Collective Mode in the Weyl Charge Density Wave Material <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mrow><mml:mi>TaSe</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mi mathvariant="normal">I</mml:mi></mml:mrow></mml:math>
Quynh L. Nguyen, Ryan A. Duncan, Gal Orenstein, Yijing Huang, Viktor Krapivin, Gilberto De La Pena, Chance Ornelas-Skarin, David A. Reis, Peter Abbamonte, Simon Bettler, Matthieu Chollet, Matthias C. Hoffmann, Matthew J. Hurley, Soyeun Kim, P. S. Kirchmann, Yuya Kubota, Fahad Mahmood, Alexander Miller, Taito Osaka, Kejian Qu, Takahiro Sato, Daniel P. Shoemaker, Nicholas Sirica, Sanghoon Song, Jade Stanton, Samuel W. Teitelbaum, Sean Tilton, Tadashi Togashi, Diling Zhu, Mariano Trigo
Abstract
We report ultrafast x-ray scattering experiments of the quasi-1D charge density wave (CDW) material (TaSe_{4})_{2}I following ultrafast infrared photoexcitation. From the time-dependent diffraction signal at the CDW sidebands we identify a 0.11 THz amplitude mode derived primarily from a transverse acoustic mode of the high-symmetry structure. From our measurements we determine that this mode interacts with the valence charge indirectly through another collective mode, and that the CDW system in (TaSe_{4})_{2}I has a composite nature supporting multiple dynamically active structural degrees of freedom.