Liquid-like thermal conduction in intercalated layered crystalline solids.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Solids typically exhibit higher thermal conductivity than liquids due to heat transfer via both transverse and longitudinal acoustic phonons.
• Liquids conduct heat solely through longitudinal vibrations, resulting in generally lower thermal conductivity.
• The distinction in phonon behavior is a fundamental characteristic differentiating solid and liquid thermal transport.

Purpose of the Study:

• To investigate the thermal transport properties of crystalline AgCrSe2.
• To understand the microscopic mechanisms behind observed thermal conductivity in this material.
• To explore the implications for thermal management in layered compounds and thermoelectric applications.

Main Methods:

• Analysis of phonon behavior in crystalline AgCrSe2.
• Investigating the role of ultrafast dynamic disorder in suppressing transverse acoustic phonons.
• Studying heat transfer mechanisms at the microscopic level.

Main Results:

• Observed liquid-like thermal conduction in crystalline AgCrSe2, defying conventional solid-state behavior.
• Identified suppression of transverse acoustic phonons due to ultrafast dynamic disorder.
• Found that surviving longitudinal acoustic phonons are responsible for the intrinsically ultralow thermal conductivity.

Conclusions:

• The study reveals a novel mechanism for ultralow thermal conductivity in crystalline solids.
• This phenomenon, driven by suppressed transverse phonons and scattered longitudinal phonons, is relevant to layered compounds with heavy intercalants.
• These findings necessitate a reevaluation of fundamental thermal transport principles and offer opportunities for designing advanced thermoelectric materials.