Anomalous thermal transport in metallic transition-metal nitrides originated from strong electron-phonon interactions

TL;DR

This paper investigates the unusual thermal transport properties of metallic transition-metal nitrides TiN and HfN, revealing large phonon thermal conductivity due to phonon gaps and strong electron-phonon interactions, with implications for device heat management.

Contribution

It uncovers the mechanisms behind anomalous thermal transport in TiN and HfN, highlighting the roles of phonon gaps and electron-phonon coupling, expanding understanding of heat conduction in metals.

Findings

Large intrinsic phonon thermal conductivity due to phonon gaps.

Significant reduction of phonon thermal conductivity by isotope and electron scattering.

Phonon component constitutes over 25% of total thermal conductivity at 300 K.

Abstract

Metallic transition-metal nitrides (TMNs) are promising conductive ceramics for many applications, whose thermal transport is of great importance in device design. It is found metallic TiN and HfN hold anomalous thermal transport behaviors compared to common metals and nonmetallic TMNs. They have extremely large intrinsic phonon thermal conductivity mainly due to the large acoustic-optic phonon frequency gaps. The phonon thermal conductivity is reduced by two orders of magnitude as the phonon-isotope and phonon-electron scatterings are considered, which also induce the nontrivial temperature-independent behavior of phonon thermal conductivity. Nesting Fermi surfaces exist in both TiN and HfN, which cause the strong electron-phonon coupling strengths and heavily harm the transport of phonons and electrons. The phonon component takes an abnormally large ratio in total thermal conductivity, as 29% for TiN and 26% for HfN at 300 K. The results for thin films are also presented and it is shown that the phonon thermal conductivity can be efficiently limited by size. Our findings provide a deep understanding on the thermal transport in metallic TMNs and expand the scope of heat conduction theory in metal.