Unlocking the Potential of Two-Dimensional Janus Superlattices: Directly Visualizing Phonon Transitions

Recent research has focused on using Anderson's localization concept to modulate coherent phonon transport by introducing disorder into periodic structures. However, designing and identifying the disorder's strength remain challenging, and visual evidence characterizing phonon localization is lacking. Here, we investigate the effect of disorder on coherent phonon transport in a two-dimensional Janus MoSSe/WSSe superlattice with a defined disorder strength. Using non-equilibrium molecular dynamics, we demonstrate that strong disorder can lead to strong phonon localization, as evidenced by smaller thermal conductivity and significantly different dependence on defect ratio in strongly disordered structures. Furthermore, we propose a novel defect engineering method to determine whether phonon localization occurs. Our work provides a unique platform for modulating coherent phonon transport and presents visual evidence of the phonon transition from localization to nonlocalization. These findings will contribute to development of phonon transport and even phononics, which are essential for thermoelectric and phononic applications.