@article{Wang2023, 
author = {Yongsong Wang and Xiao Guo and Siwen You and Junjie Jiang and Zihan Wang and Fangping Ouyang and Han Huang},
title = {Giant quartic-phonon decay in PVD-grown α-MoO3 flakes},
year = {2023},
journal = {Nano Research},
volume = {16},
number = {1},
pages = {1115-1122},
keywords = {layered materials, anisotropy, synthesis, phonon–phonon coupling, ultralow phonon thermal conductivity},
url = {https://www.sciopen.com/article/10.1007/s12274-022-4734-3},
doi = {10.1007/s12274-022-4734-3},
abstract = {Elementary excitations, such as in-plane anisotropic phonons and phonon polaritons (PhPs), in α-MoO3 play key roles in its outstanding physical properties like high carrier mobility and ultralow phonon thermal conductivity ( κP). Understanding the excitation mechanisms like phonon–phonon interactions is the most fundamental step to further applications. Here, we report on the systematic Raman investigations on phonon anisotropy and anharmonicity of representative Mo–O stretching vibration phonon modes (SVPMs) in physical vapor deposition (PVD)-grown α-MoO3 flakes. Polarizations of SVPMs verify the phonon anisotropy. The abnormal temperature dependence of SVPMs reveals that giant quartic-phonon decay dominates the phonon anharmonicity in α-MoO3. An ultrashort phonon lifetime of ~ 0.34 ps gives evidence of theoretically predicted ultralow  κP in α-MoO3. Our findings give deep insight into the phonon–phonon interactions in α-MoO3 and provide an indicator for its extreme thermal device applications.}
}