Xin WU

Phonon coherence elucidates the propagation and interaction of phonon quantum states within superlattice, unveiling the wavelike nature and collective behaviors of phonons. 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. 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.

The development of emerging technologies, such as quantum computing and semiconductor electronics, emphasizes the growing significance of thermal management at cryogenic temperatures. Herein, by designing isotope interfaces based on the Golomb ruler, we achieved effective suppression of the phonon thermal transport of cryogenic graphene. The pronounced disordering of the Golomb ruler sequence results in the stronger suppression of thermal transport compared to other sequences with the same isotope doping ratio. We demonstrated that the Golomb ruler-based isotope interfaces have strong scattering and confinement effects on phonon transport via extensive molecular dynamics simulations combined with wave packet analysis, with a proper correction for the missing quantum statistics. This work provides a new stream for the design of thermal transport suppression under cryogenic conditions and is expected to expand to other fields.

In two-dimensional (2D) heterosystems, the contribution of coherent phonon transport makes superlattices with high interface density exhibit unexpected high thermal conductivity. Herein, inspired by mathematics, we demonstrate efficient suppression of phonon thermal transport in a 2D heterosystem constituted of graphene and hexagonal boron nitride based on the Golomb ruler sequences. This design realizes extreme suppression of thermal conductivity with a minimal number of interfaces, and without any defects or dopants. Extensive numerical simulations combined with wave packet analysis show that the Golomb ruler sequence largely cancels the coherent phonon transport. This work, as the first attempt for realizing novel thermal physics using the mathematically inspired Golomb ruler design, provides a new and efficient solution for the suppression of thermal transport in 2D heterosystems.