Speaker
Description
The study of transient, far-from-equilibrium states in complex materials can offer profound insights into their microscopic properties, particularly when multiple observables are examined simultaneously. A central question in this field is whether atomic lattice displacements can be accurately tracked and controlled.
In this work, we investigate the ultrafast dynamics of Tellurium (Te) and Tungsten ditelluride (WTe
Tellurium has four zone-center optical phonons, three of which are Raman active. These include the non-degenerate A
We conducted TR-R and TR-SHG measurements on WTe
A notable (~ 90°) phase shift in the shear mode, as induced by varying the pump fluence, is observed in both the TR-R and TR-SHG signals, and along the two crystallographic directions. This finding suggests that the phase shift of the coherent oscillation is induced by a true fluence-dependent modification of the initial phase of the atomic displacements, allowing for a precise control of the atom dynamics.
These findings provide new perspectives on the interactions between coherent phonons and the electronic and lattice properties of complex materials, emphasizing the importance of selecting appropriate experimental observables to extract quantitative information on material properties. Notably, we demonstrate that pump fluence can serve as an effective tool to significantly adjust and tune the initial oscillation phase of coherent displacements.