Condensed Matter and Materials

Work in condensed matter theory covers several broad areas. This work is closely coupled to the experimental work of Professor Kelton's group on Ti-based quasicrystals. In the simulations, candidate structures for quasicrystals and "rational approximants" (large unit-cell crystals with local structures similar to those of quasicrystals) are generated using canonical-cell methods. The candidate structures are relaxed on the basis of the interatomic forces. It is hoped that this work can contribute to the effort to find better hydrogen-storing quasicrystals.

Professor Yang's group develops and applies first-principles approaches (many-body perturbation theory) to study excited states in a range of solids, from bulk semiconductors to low-dimensional nanostructures. In particular, they focus on the carbon and silicon based 1-dimensional nanostructures, e.g., nanowires and nanoribbons, which have displayed excellent electrical and optical performance to date. Their research is of help to reveal how excited states, such as the quasiparticle band energy and optical response, are modified by electron-electron and electron-hole interactions. Moreover, their fundamental study will provide necessary knowledge to control excited states and design novel functional materials for nanoelectronics and photovoltaic applications.