Ajou Condensed Matter Theory Group
Flat band systems
In a flat band, electrons are immobile due to the quantum interference effect. As a result, the flat band systems have been considered ideal platforms to study many-body physics. Due to recent experimental progress in realizing such systems, such as the twisted bilayer graphene and kagome-like materials, the research on flat band systems has become one of the most intensive research fields in condensed matter physics. We are interested in a broad range of subjects in flat band systems from the fundamental band theory to strongly correlated phenomena.
Geometric aspects in solid-state physics
Quantum states describing a solid has an intriguing geometric nature in momentum space. Namely, one can apply geometric notions such as the curvature and metric to the Bloch wave function, which is the quantum eigenstate of a solid. From the curvature of the Bloch wave function, one can study the semiclassical motion of electrons and topological aspects in a solid, which have become one of the basic knowledge to understand solid-state physics nowadays. On the other hand, people do not know much about how the distance concept of the Bloch wave function appears in solid-state physics. We study how the geometric properties of the Bloch wave function are manifested in a variety of condensed matter phenomena.
Many-body physics
Electrons in a solid interact with each other via the Coulomb force. Many exciting condensed matter phenomena such as the unconventional superconductivity, Kondo effect, magnetism, Wigner crystal, and fractional quantum Hall effect are due to the interaction between electrons. Such systems are called the strongly correlated electron systems. Unlike the non-interacting systems, which can be solved exactly, the strongly correlated systems are extremely complicated and only a few examples are exactly solvable. We explore novel approximate methods to deal with those correlated problems and discover novel phenomena arising from the correlations.
Orbital Rashba effect
Due to the relativistic effect, a moving electron in an electric field feels the magnetic field. The Zeeman energy splitting from this relativistic magnetic field is called the Rashba effect. Being a relativistic effect, this phenomenon can be hardly observed. However, in a solid with an inversion symmetry breaking, one can have the same effect with the help of the orbital degrees of freedom. This is called the orbital Rashba effect, and the energy splitting is large enough to be observed experimentally. We study the geometric nature underlying this effect as well as exotic condensed matter phenomena originating from it.
Nanomaterials
Our group is interested in the physical properties of various low-dimensional systems such as graphene, graphene nanoribbons, TMDCs, and topological insulator nanowires. We study how those systems can be applied to nano-technologies such as semiconductors, thermoelectric, photovoltaic, and spintronic devices.
Get in touch with us via [jwrhim(at)ajou.ac.kr]