Dimer rattling mode induced low thermal conductivity in an excellent acoustic conductor

Abstract

A solid with larger sound speeds exhibits higher lattice thermal conductivity (k_{lat}). Diamond is a prominent instance where its mean sound speed is 14400 m s-1 and k_{lat} is 2300 W m-1 K-1. Here, we report an extreme exception that CuP2 has quite large mean sound speeds of 4155 m s-1, comparable to GaAs, but the single crystals show a very low lattice thermal conductivity of about 4 W m-1 K-1 at room temperature, one order of magnitude smaller than GaAs. To understand such a puzzling thermal transport behavior, we have thoroughly investigated the atomic structure and lattice dynamics by combining neutron scattering techniques with first-principles simulations. Cu atoms form dimers sandwiched in between the layered P atomic networks and the dimers vibrate as a rattling mode with frequency around 11 meV. This mode is manifested to be remarkably anharmonic and strongly scatters acoustic phonons to achieve the low k_{lat}. Such a dimer rattling behavior in layered structures might offer an unprecedented strategy for suppressing thermal conduction without involving atomic disorder.

arXiv commentfour figures and one table in the main text

References in corpus (4)

• Giant Anharmonic Phonon Scattering in PbTe
• HORACE: software for the analysis of data from single crystal spectroscopy experiments at time-of-flight neutron instruments
• Liquid-like thermal conduction in a crystalline solid
• Effects of Grain Boundaries and Defects on Anisotropic Magnon Transport in Textured Sr14Cu24O41

Cited by in corpus (1)

• Low and Anisotropic Thermal Conductivity in Mixed-Valent Sn${}_2$S${}_3$