Phononics
What can phonons do? This is a fundamental question that we keep on asking ourselves for years and is the long-time research theme in our laboratory. Phononics is an emerging research field aiming to answer this question.  In recent years, we have made several important discoveries including room temperature ballistic thermal conduction, phonon waveguides, and thermal rectification. We are currently exploring many interesting properties of phononics; including their interactions with electrons and photons, and studying their quantum properties.

Ballistic thermal conduction
Unlike ordinary diffusive thermal conduction, ballistic thermal conduction indicates that wave-properties of phonons can be transmitted without dissipation. Thus it will display many interesting phenomena unfound before. We have recently discovered ballistic thermal conduction over 8.3μm in SiGe nanowires at room temperature. The discovery will enable many novel applications such as phonon waveguides or phononic crystals. Particularly, some interesting quantum effects could be hidden inside the nanowires that we are eagerly to dig them out.

One-dimensional heat transfer
Heat transfer in one-dimensional (1D) system has puzzled many generations of physicists. For the first time, now it is possible to experimentally investigate this problem. We are developing state-of-the-art techniques to investigate the heat transfer phenomena in 1D systems. The above image displays a 1mm-long nanotube, in which we demonstrate that its thermal conductivity increases with its length! Thus we prove that non-Fourier thermal conduction in real materials can persist over 1mm distance at room temperature!

Thermoelectricity for energy harvesting
Thermoelectric devices can directly convert heat into electricity. They are ideal next-generation clean energy resources.  We are conducting various schemes to enhance the efficiency of thermoelectric devices, with special focuses on utilizing new phenomena of heat conduction in nanoscales. 

Subwavelength photonics
Artificially-engineered structures like metamaterials are capable of exhibiting physical properties far beyond those of natural materials.  Thus one can design their own "atoms" or "molecules" with specific optical functionalities.  We are exploring this new field with aids from electromagnetic simulations and optical experiments.

Superresolution microscopy
When the size of a lens is reduced to microscales, it can display surprising optical phenomena unexpected before. We recently discovered that the microlenses will enable far-field, broadband, high-speed, large area, wide angle superresolution capabilities with very low costs. Together with Prof. Shi-Wei Chu of Physics department, we are currently investigating the underlying mechanisms, and at the same time, exploring their potential applications in medicine or biology.

Nanomechanical resonators
High frequency nanomechanical resonators promise to be next-generation RF signal filters and processors.  Moreover, they are capable of detecting the mass of a single atom and the quanta of a single spin.  We are developing various experimental and theoretical schemes to approach these limits.  Ultimately, we hope that our works open a new route for sensing atoms or spins.

High pressure synthesis of new materials
Materials synthesized under high-pressure and high-temperature conditions usually exhibit new structures or new phases unfound in conventional synthesis.  We are particularly interested in using this technique to explore nanomaterials or complex oxides with unusual electronic ground states, such as charge density waves, magnetism, and superconductivity.