Models of ballistic propagation of heat at low temperatures

TL;DR

This paper compares different theoretical models of heat conduction at low temperatures, focusing on ballistic and wave-like heat pulse propagation in NaF, where traditional Fourier law fails.

Contribution

It evaluates the performance of various theories in describing ballistic and wave-like heat propagation in low-temperature conditions.

Findings

Fourier law is inadequate at low temperatures.

Certain models better capture ballistic heat propagation.

Wave-like heat pulse behavior is demonstrated in NaF.

Abstract

Heat conduction at low temperatures show various effects that cannot be described by the Fourier law, like the second sound and ballistic propagation. In this paper the performance of various theories is compared in case of ballistic and wave like propagation of heat pulses in NaF.