Pushing the Thermal Conductivity Limit by Decoupling Dual-Channel Phonon Transport in Crystals

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Controlling thermal conductivity in crystalline materials is crucial for advanced technological applications.
• Conventional methods often face trade-offs between suppressing particle-like (κp) and wave-like (κc) phonon transport.

Purpose of the Study:

• To introduce a novel design principle for achieving ultralow thermal conductivity in crystalline materials.
• To concurrently suppress both particle-like and wave-like phonon transport channels.

Main Methods:

• Proposed a 'heavy-light and soft-stiff' structural motif combining atomic mass and bonding stiffness.
• Employed first-principles calculations to analyze phonon spectrum and transport mechanisms.
• Utilized high-throughput screening to identify candidate materials.

Main Results:

• The 'heavy-light and soft-stiff' architecture induces a hierarchical phonon spectrum, enhancing scattering and reducing κp.
• Light atoms with stiff bonds disrupt phonon coherence, effectively lowering κc.
• Identified Tl4SiS4 and Tl4GeS4 as promising candidates with significantly suppressed thermal conductivity in both channels.

Conclusions:

• The proposed design principle offers a new paradigm for phonon engineering.
• This approach overcomes the conventional trade-off between κp and κc, enabling ultralow thermal conductivity.
• Demonstrated the generality of the mechanism using a 1D triatomic chain model.