Thermal transport of boron pyrochlore lattices

Abstract

Pyrochlore lattice (PL) is a type of special lattice, which shows unique electronic and magnetic properties, such as flat band, spin frustration and spin liquid. However, its lattice thermal transport has never been reported. Here, we study phonon spectra and lattice thermal conductivities of pyrochlore born structures. Like the case of electron band structure, there are flat bands appearing in the phonon spectra. The flat bands not only lead to the zero group velocities of phonons but also induce strong phonon scatterings. As a result, the lattice thermal conductivity of pyrochlore born is very low (5.89 W/mK at room temperature). Thermal transport in another pyrochlore-like boron structure is also investigated. Due to the existence of band gaps in the phonon spectra, the phonon scatterings are significantly suppressed in the structure. Although there are more flat bands in the pyrochlore-like boron structure, its thermal conductivity (13.94 W/mK) is higher than that of the standard pyrochlore boron. This reveals the effect of the bandgap engineering on the thermal transport. Our results provide a fundamental reference for further studies on mechanical and thermal properties of PL structures.