Phonon hydrodynamic transport and Knudsen minimum in thin graphite

The recent experimental results reveal that thermal conductivity of thin graphite increases with the decrease of thickness. The exact mechanism of this phenomenon still remains elusive. Here, based on the one-dimensional Guyer-Krumhansl model and the non-local boundary condition, we show that decreasing thickness of thin graphite enhances its thermal conductivity. Whether Knudsen minimum phenomenon arises in phonon transport of thin graphite is also an unsolved scientific problem. By using the Guyer-Krumhansl model with the non-slip boundary condition in the width direction and the non-local boundary condition in the thickness direction for thin graphite, we find that the Knudsen minimum phenomenon can occur when the ratio of the thickness to width is less than 0.26. (C) 2020 Elsevier B.V. All rights reserved.