Topological insulators (TIs) and topological crystalline insulators (TCIs) are new quantum phases with strong spin-orbit coupling leading to topologically protected metallic surface states within the bulk band gap. Some of the known TIs and TCIs are based on chalcogenides of lead, bismuth and tin. Our group is interested in investigating the chemical aspects and local structure of these metal chalcogenide TIs ad TCIs. We pursue research to modify the electronic structure of TIs and TCIs by chemical doping route and thereby optimize their thermoelectric properties.
Weak topological insulators (WTIs) are new quantum state of matter which is topologically equivalent to a stack of 2D TI layers with even number of Dirac cones on the side surfaces. Hitherto, experimentally verified 3D WTIs are hosted by layered crystal structure with heavy constituent elements which enables WTIs to shine light on minimum lattice thermal conductivity and expected to be important candidates for thermoelectrics. Our group is interested in the investigation and optimization of thermoelectric properties of various weak topological insulators.