Probing the Intralayer and Interlayer Dynamics of the Charge Density Wave Phases in 1T-TaS₂

1T-TaS₂ is a van der Waals transition metal dichalcogenide (TMD) material with a rich phase diagram consisting of unique ‘Star of David’ charge density wave (CDW) states in thermal equilibrium, including the coexistence of superconducting and commensurate CDW states. Numerous studies have characterized the equilibrium phases through observables such as resistivity, optical reflectivity, and scanning tunneling microscopy, but experiments to study the nature of the recently discovered ‘hidden’ metastable CDW state have been less revealing. Of the myriad of TMDs, 1T-TaS₂ is the only one that exhibits a low-temperature non-thermal switching from an insulating ground state to a gapless ‘hidden’ metallic state, not to mention its extremely large temporal range of tunable lifetimes. We performed an ultrafast X-ray diffraction experiment to access dynamic observables, the coherent oscillations from independent structural and electronic scattering peaks, to reveal directional and chiral dependencies that unveil the complexity of the domain structure that prior experiments failed to capture, particularly the nature of the interlayer and intralayer domain dynamics and their role in the commensurate CDW-hidden CDW nonequilibrium transition.