Presentation Information
[7p-N105-5]Machine-learned molecular dynamics uncover phonon coherence and lower bounds of thermal transport in disordered superlattices
〇(P)Xin Wu1, Zheyong Fan2, Penghua Ying3, Masahiro Nomura1 (1.Univ. of Tokyo, 2.Bohai Univ., 3.Tel Aviv Univ.)
Keywords:
Phonon coherence,Machine learning,Molecular dynamics
Phonon thermal transport exhibits significant potential in nanoscale thermal physics, especially in semiconductors and insulators where the lattice thermal conductivity is almost entirely derived from lattice vibrations. In periodically alternating nanostructures known as superlattices, composed of two or more different materials, phonons experience multiple reflections and interference at periodic interfaces, leading to the formation of unique phonon spectra and coherent transport. Disordered superlattices, with their complex interface scattering and localization effects, usually serve as valuable systems for contrasting with perfect superlattices. They have also been extensively studied in the context of phenomena such as Anderson localization, highlighting their potential as unique platforms for broadband quenching of phonon transport. However, the role of phonon coherence within disordered superlattices has remained overlooked. Taking MoSe2/WSe2 lateral heterostructures as a model system, we demonstrate that the intricate interplay between wavelike and particlelike phonons, previously observed in perfect superlattice only, also occurs in disordered superlattice. By employing molecular dynamics simulation based on a highly accurate and efficient machine-learned potential constructed herein, we observe a nonmonotonic dependence of the lattice thermal conductivity on the interface density in both perfect and disordered superlattice, with a global minimum occurring at relatively higher interface density for disordered superlattice, as shown in Figure b. The counterintuitive phonon coherence contribution can be characterized by the lagged self-similarity of the structural sequences in the disordered superlattice. Our findings extend the realm of coherent phonon transport from perfect superlattice to more general structures, which offers more flexibility in tuning thermal transport in superlattices.