Condensed matter systems, that include insulators, semiconductors, metals and superconductors among many others, consist of many particles, of the order of ten to the twenty three. At the microscopic level, the dynamics of individual particles is governed by the well established theoretical framework, quantum mechanics. However, it is extremely difficult to understand and predict macroscopic behaviors of a whole system, starting from the microscopic theory. For the past 30 years, it has become clear that understanding macroscopic properties is not a matter of mere application of the known physical laws. Instead, collective behaviors are governed by novel organizing principles, which are not manifest from the microscopic rule of dynamics. Currently, the primary goal of my research is to identify new dynamical principles that are behind novel emergent phenomena in gapless phases of matter such as unconventional metals and systems near quantum critical points, and to apply those principles to understand physical properties observed in experiments. To achieve the goal, I use various theoretical tools, including quantum many-body theory and quantum field theory. I am also interested in the interdisciplinary research areas between condensed matter physics, string theory and gravitational theory. Recently I have been developing the notion of `quantum renormalization group' where coupling constants are promoted to quantum mechanical operators to make a connection between general D-dimensional quantum many-body systems and (D+1)-dimensional quantum theory of gravity via holography. I am trying to use the quantum renormalization group scheme to understand strongly coupled field theories that are hard to solve otherwise.

Strongly Correlated Quantum Many-Body Systems, Quantum Field Theory, Quantum Critical Phenomena, Non-Fermi Liquids, Holography

Dear Prospective Graduate Student,

My main research area is strongly correlated many-body system. When many particles (as many as ten to the twenty-third power of particles) are strongly correlated (interacting) with each other, they can behave very differently than either when there are only a few particles or when they are not strongly correlated. Because of the enormous amount of degrees of freedom and the strong correlation between them, it is impossible to predict measurable physical properties of a system from the dynamics of individual particles. However, as we observe them in a longer distance scale, we notice that there are some orders (patterns) in their fluctuations. Sometimes, these emerging patterns can be described in surprisingly simple and beautiful ways. The goals of my research are to understand various emergent phenomena in correlated quantum many-body systems using quantum field theory and holographic description.

If you want to know more about my research, please contact me via email.

Sung-Sik Lee