  The thermal conductivity of boron arsenide (BAs) is believed to be influenced
by phonon scattering selection rules due to its special phonon dispersion.
Compression of BAs leads to significant changes in phonon dispersion, which
allows for a test of first principles theories for how phonon dispersion
affects three- and four-phonon scattering rates. This study reports the thermal
conductivity of BAs from 0 to 30 GPa. Thermal conductivity vs. pressure of BAs
is measured by time-domain thermoreflectance with a diamond anvil cell. In
stark contrast to what is typical for nonmetallic crystals, BAs is observed to
have a pressure independent thermal conductivity below 30 GPa. The thermal
conductivity of nonmetallic crystals typically increases upon compression. The
unusual pressure independence of thermal conductivity of BAs shows the
important relationship between phonon dispersion properties and three- and
four-phonon scattering rates.
