Topological edge states in novel 2M phase WS
2
Very recently, Fang et al. discovered a new phase of WS2 - called the 2M phase - where 1T’ monolayers of WS2 crystallize in a monoclinic lattice very different from any previously observed TMDC phases. This new phase is found to be superconducting and at the same time theoretically predicted to be topologically non-trivial, potentially making it the first ever topological superconductor reported among the TMDC family.
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Research Highlights
Broad area of research interest is in studying various properties associated with layered two dimensional materials using Density Functional Theory (DFT).
Topological properties of Janus Monolayers of 1T' WTe
2
Transition metal dichalcogenides (TMDCs) are an interesting class of materials both due to the layered nature, marking their similarity to graphene, and due to the wide range of electronic properties depending on the composition and structure of the material. An interesting class of materials derived from TMDCs are Janus monolayers, where the usual MX2 sandwich structure of monolayer TMDCs (the metal M atom sandwiched between two chalcogen X atoms) is replaced by an MXY form, with two different chalcogen atom layers above and below the metal layer.The breaking of out of plane symmetry in Janus monolayers can potentially give rise to interesting properties (such as breaking of inversion symmetry and Rashba splitting) which can be completely different from the parent monolayers.
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Chirality-tunable BCD and non-linear Hall in chiral crystals
Chiral materials are characterized by their lack of improper symmetries such as inversion, mirror plane, and roto-inversion. Owing to this absence of symmetries, we propose chiral systems as ideal platforms to study the Berry curvature dipole-induced non-linear Hall effects. Using state-of-the-art first-principles computations, in conjunction with symmetry analyses, we explore a variety of chiral material classes -- metallic NbSi2, semiconducting elemental Te, insulating HgS, and topological multifold semimetal CoSi. We present the emergence and tunability of the Berry curvature dipole in these chiral materials. In particular, we demonstrate that the two enantiomeric pairs exhibit an exactly opposite sign of the Berry curvature dipole. Our predictions put forward chiral materials as an emerging class of materials to realize non-linear Hall phenomena and highlight an as-yet-unexplored aspect of these systems.
Non-stoichiometric KRhO
2
Experimental collaboration with Dr. Thirupathaiah Setti, SNBNCBS
KRhO2 and its derivatives are colossal thermoelectric materials -- these enable efficient conversion of temperature differences to electrical voltages.
We provided theoretical support in the study of low energy electronic structure of thermoelectric K0.65RhO2, giving more insight into the observed ARPES data and the band dispersion associated with the system. The key finding is the observation of a new high energy bosonic mode, which has important implications for explaining the unconventional properties of this system.
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Puckered layer geometry
Electrically tunable topological phase transition in Phosphorene
Black Phosphorus is a thermodynamically stable form of Phosphorus, having a layered structure similar to Graphene and TMDCs. With its unique puckered layer geometry, this material is gathering more interest in terms of nanoelectronic and nanophotonic applications. Phosphorene, the low dimensional analog of black P, have been predicted to display a normal insulator-to-topological insulator phase transition on the application of an electric field.