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.
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
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
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
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
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