Fermi Surface Nesting and Phonon Frequency Gap Drive Anomalous Thermal Transport

Area of Science:

• Solid-state physics
• Materials science
• Condensed matter physics

Background:

• Lattice thermal conductivity (kL) typically decreases with temperature due to phonon-phonon scattering.
• Phonon-electron interactions are usually weaker than phonon-phonon interactions in most crystals.

Purpose of the Study:

• Investigate conditions for a temperature-independent lattice thermal conductivity in metals.
• Identify novel heat transport regimes in solids.

Main Methods:

• First-principles calculations.
• Analysis of phonon dispersions and Fermi surface nesting.
• Study of electron-phonon and phonon-phonon interaction strengths.

Main Results:

• Demonstrated that kL can become nearly independent of temperature in metals with nested Fermi surfaces and large phonon frequency gaps.
• Showed that electron-phonon interactions can dominate over phonon-phonon interactions under these conditions.
• Observed this phenomenon in group V transition metal carbides (vanadium, niobium, and tantalum carbides).

Conclusions:

• Identified a new heat flow regime driven by the interplay of Fermi surfaces and phonon dispersions.
• This finding offers insights into the physics of heat conduction in solids.
• Suggests this behavior may occur in other metal compounds with similar electronic and phononic structures.