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arXiv · 1910.13780

Ultralow lattice thermal conductivity of monolayer penta-silicene and penta-germanene

Zhibin Gao·Zhaofu Zhang·Gang Liu·Jian-Sheng Wang
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Abstract

We study the lattice thermal conductivity of two-dimensional (2D) pentagonal systems, such as penta-silicene and penta-germanene. Penta-silicene has been recently reported, while the stable penta-germanene, belonging to the same group IV element, is revealed firstly by our ab initio calculations. We find that both penta-silicene and penta-germanene at room temperature have ultralow lattice thermal conductivities $κ$ of 1.29 W/mK and 0.30 W/mK respectively. To the best of our knowledge, penta-germanene may have the lowest $κ$ in 2D crystal materials. We attribute ultralow $κ$ to the weak phonon harmonic interaction and strong anharmonic scattering. A small phonon group velocity, a small Debye frequency, a large Gruneisen parameter, and a large number of modes available for phonon-phonon interplay together lead to the ultralow $κ$ of penta-silicene and penta-germanene. These discoveries provide new insight into the manipulation of ultralow $κ$ in 2D materials and highlight the potential applications of designing silicon and germanium based high thermoelectric materials.

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Zhibin Gao, Zhaofu Zhang, Gang Liu, Jian-Sheng Wang. 2019-10-30. Ultralow lattice thermal conductivity of monolayer penta-silicene and penta-germanene. https://doi.org/10.1039/c9cp05246a

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