My research interests lie in quantum condensed matter theory. One major direction of my work is to study electronic systems with strong interaction. Surprisingly, strongly correlated electrons in various experimental systems can sometimes (for example, fractional quantum Hall effect) be understood from collective degrees of freedom which are fundamentally dif-ferent from electronic degrees of freedom. I am interested in frustrated magnets and high-Tcsuperconductors where such fascinating physics may be realized. I am also interested in topological aspects of condensed matter system such as topological defects and topological band insulators. In these systems there are often topologically protected excitations and effects that can be detected experimentally.