Ultrafast resonant soft x-ray diffraction dynamics of the charge density wave inTbTe3

Understanding the emergence of collective behavior in correlated electron systems remains at the forefront of modern condensed matter physics. Disentangling the degrees of freedom responsible for collective behavior can lead to insights into the microscopic origins of emergent properties and phase transitions. Utilizing an optical pump, resonant soft x-ray diffraction probe we are able to track, in real time, the dynamics of the charge density wave (CDW) in ${\mathrm{TbTe}}_{3}$, a model system that violates traditional views of a Fermi surface nested CDW. We observe coherent oscillations corresponding to the CDW amplitude mode at $2.4$ THz and a coherent optical phonon mode at $\ensuremath{\sim}1.7\phantom{\rule{0.16em}{0ex}}\mathrm{THz}$. We show how such observations reveal the anisotropic energy optimization between in-plane Te charge density modulations and the three-dimensional lattice coupling.