Phonon and magnon dynamics is crucial for understanding many material properties such as thermal transportation, thermal expansion, and phase transformation with many important science and engineering applications in energy materials, structural materials, and nano-devices.

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Magnon-phonon interaction

Spin waves and phonons are strongly coupled in many ferromagnetic and antiferromagnetic structures.

Application: controlling heat flow on nanoscale, manipulating spin coherence

Supported by: Thermal Transport Process Program, CBET, NSF

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Interfacial Thermal Transport

We study the effects of phonon anharmonicity on the interfacial thermal conductance.

Application: improving interfical thermal conductance performance

Thermal Transport under High Pressure

Thermal transport at the layer interfaces in lower mantle is dominated by conduction. We study the transport in materials under these extreme environments.

Application: modeling the evolution of the eather interior

Phase Transformation

The role of phonons and magnons in phase transformation. For example, vibrational entropy in stabilizing or destabilizing the amorphous phase was determined by measuring the phonons through the glass transition.

Application: making tougher engineering materials

Phonon engineering

Lattice thermal transport can be surpressed by phonon nesting, resonance, nanostructure, and etc

Application: reducing the thermal conduction and improving figure of merit of thermoelectrics

Negative Thermal Expansion

Pure quartic phonon modes in scandium flouride stiffen at elevated temperature and large side motions of the flourine atoms pulls their neighbouring scandium atoms together.

Application: controlling the thermal expansion of structural materials

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Phonon anhamonicity and lifetime

Anharmonicity of bulk or low-dimension materials (metals, alloys, oxides, …) due to phonon-phonon interactions can be probe by their phonon Grüneisen parameters and lifetime.

Application: correlate anharmonicity and their thermodynamical effects