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arXiv · 1708.08158

Glass-Like Thermal Conductivity in Nanostructures of a Complex Anisotropic Crystal

Annie Weathers·Jesus Carrete·John P. Degrave·Jeremy M. Higgins·Arden L. Moore·Jaehyun Kim·Natalio Mingo·Song Jin·Li Shi
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Abstract

Size effects on vibrational modes in complex crystals remain largely unexplored, despite their importance in a variety of electronic and energy conversion technologies. Enabled by advances in a four-probe thermal transport measurement method, we report the observation of glass-like thermal conductivity in ~20 nm thick single crystalline ribbons of higher manganese silicide, a complex, anisotropic crystal with a ~10 nm scale lattice constant along the incommensurate c axis. The boundary scattering effect is strong for many vibrational modes because of a strong anisotropy in their group velocities or diffusive nature, while confinement effects are pronounced for acoustic modes with long wavelengths along the c axis. Furthermore, the transport of the non-propagating, diffusive modes is suppressed in the nanostructures by the increased incommensurability between the two substructures as a result of the unusual composition of the nanostructure samples. These unique effects point to diverse, new approaches to suppressing the lattice thermal conductivity in complex materials.

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Annie Weathers, Jesus Carrete, John P. Degrave, Jeremy M. Higgins, Arden L. Moore, Jaehyun Kim, Natalio Mingo, Song Jin, Li Shi. 2017-10-28. Glass-Like Thermal Conductivity in Nanostructures of a Complex Anisotropic Crystal. https://doi.org/10.1103/physrevb.96.214202

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