I will use computational and theoretical approaches to understand and predict topological effects of materials in their optically excited states. Currently, I am wrapping-up an investigation on a novel interband index T for 2D systems (such as transition metal dichalcogenides). We showed that T may provide gauge-invariant excitonic optical selection rules and help characterize valley topology in excited states. Next, I will develop robust DFT-based computational schemes to calculate T in other materials beyond tight-binding frameworks. I will simultaneously study T in non-Hermitian systems; which are realistic quantum systems with gain and loss due to interactions with optical fields and environments. I am interested in how this may elucidate physics at ‘exceptional points’, and on quasiparticle lifetime effects (both critical for enhanced light-matter interaction and quantum efficiency). Compared against heavily-explored ground state topology and lossless systems, these studies may offer new insight into the design of energy-harvesting and energy-conversion systems.
Advisor: Ting Cao – Physics