My primary research interest is modeling condensed matter systems using analytical and numerical approaches. I have an interest in material properties which may prove to have technological value. My technical interests cover various tools used in condensed matter theory, ranging from numerical electronic structure calculations using density functional theory to more analytical field theoretical approaches.
During my Ph.D. studies done under the supervision of Dr. Allan H. MacDonald, I have focused on studying the properties of monolayer, bilayer and multilayer graphene, and its applications to new devices. First, we investigated the influence of spin-orbit coupling on an isolated graphene sheet by deriving explicit expressions for spin-orbit interaction induced gaps, and performed ab initio electronic structure calculations to confirm the results. Next, using ab initio density functional theory and a tight-binding model self-consistent Hartree calculation, we confirmed that the energy gap in graphene bilayers can be controlled by applying external electric fields, suggesting an application for graphene bilayers as tunable gap semiconductors.
Recently, we predicted that neutral graphene bilayers are pseudospin magnets, in which the charge density contribution from each spin and valley spontaneously shifts to one of the two layers. This suggests the possibility of a new electronic device scheme called pseudospintronics. Furthermore, we demonstrated that room-temperature excitonic condensation is possible in graphene bilayers, suggesting new electronic device applications based on unusual collective transport of bilayer excitonic condensates. We also developed a simple diagrammatic method to analyze the low energy properties of arbitrarily stacked graphene sheets. This showed that at low energies, arbitrarily stacked N-layer graphene is described by a set of pseudospin doublets, which gives a new quantized Hall conductivity sigma_H = (4 e^2/h)(N/2+n) where n a non-negative integer for any stacking sequence.
Currently, I am working on various topics such as electronic properties of bilayer graphene nanoribbons using the ab initio density functional theory, effects of spin-orbit coupling in graphene edge states using a tight-binding model, perturbative renormalization group theory of bilayer graphene instabilities, the edge state magnetism calculation in graphene at finite temperature using the stochastic Landau-Lifshitz-Gilbert equation, electronic structure calculations at the heterostructure interface between Mott insulators using the ab initio density functional theory, and effects of disorder and internal dynamics on domain-wall propagation.
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