

Twodimensional Materials  In 1946, the Canadian theoretical physicist P R Wallace predicted extraordinary electronic structure of the twodimensional hexagonal honeycomb lattice of graphite called graphene.[1]
However, it took many decades in 2004 for its experimental realization, when physicists A Geim and K Novoselov successfully exfoliated oneatomthick graphene by scotch tape method.[2,3]
Since then, researchers are fascinated by the quantum world of twodimensional materials to know and exploit how electrons behave and interact in reduced dimension as opposed to the conventional threedimensional world.
Many extraordinary twodimensional materials have been discovered since such as transitionmetal dichalcogenides, hexagonal boron nitride, phosphorene and oxides, to name a few.[4,5,6,7]





Strong electron correlation and band topology have led to the discovery of twodimensional topological insulators, Dirac and Weyl semimetals and superconductors.[8,9]
Further, easy tunability of their physical properties and enormous possibilities in van der Waals 'lego' heterostructures have led to the discovery of many emergent phenomena. If they live up to their applicable expectations, these twodimensional materials have potential for disruptive technologies.
Our group is focused on investigating and exploiting electron correlation and band topology to study edge states, magnetism, superconductivity and topological states in twodimension.[10,11,12,13,14,15,16,17,18]



Quantum Materials 
Quantum manybody interactions among electrons, orbitals, spins, and crystal lattice along with the manifestation and interplay between strong interaction, quantum fluctuation, entanglement, topology, and reduced dimensionality often lead to exotic and emergent quantum phenomena.[1,2,3,4] The schematic demonstrating various degrees of freedom that can be manipulated by external perturbation is adopted from Ref.[5] Such quantum phenomena in materials must be exploited in the future quantum devices and operando control of spin, charge, orbital, lattice and topology will require concerted and collaborative quantum materials research and development efforts. Much progress in quantum materials relies on accurate simulation using quantum mechanical methods. We apply firstprinciples quantum theories to account for manybody interactions realistically, and correctly understand, predict and manipulate the collective and emergent phenomena in quantum materials in close collaboration with the experimental colleagues.



Quantum Magnetism 
The magnetism in materials, that has impacted our everyday life, arises from the spin degree of freedom of electrons, which is a quantum concept derived from Dirac's relativistic theory. Further, magnetic moments on a lattice interact via exchange interactions with competing electronic kinetic energy and Coulomb interaction leads to various magnetic phases. However, miniaturization of bulk magnetism into twodimension was thought to be impossible following HohenbergMerminWagner theorem until recently.[1,2,3]
Since magnetic anisotropy and longrange interaction breaks the continuous rotational symmetry of Heisenberg spin Hamiltonian, magnetism in twodimension is possible at finite temperature, and indeed discovered very recently in Cr_{2}Ge_{2}Te_{6} and CrI_{3}.[4,5]
This brings enormous opportunities to explore 2D magnetic states and exploiting them to control magnetic properties with various external perturbations.[6]
The bottleneck for the practical application at the moment is these 2D magnetic states lives at a very low temperature, while any practical applications will require their availability at roomtemperature.
We are interested in the interplay of electronic kinetic energy, Coulomb interaction, and spinorbit coupling to understand magnetism in strongly correlated bulk systems, 2D magnets and heterostructures, and proximate quantum spin liquid systems.



Sustainable Energy Materials 
Discovery and concurrent property optimization are necessary to mitigate future energy demands in a cleaner way. However, these processes are expensive and timeconsuming, and it is recognized that the entire process would be more rapid and costeffective if predictive mathematical modelling and simulations shortcircuit the experimental efforts. We employ quantum chemical models with chemical accuracy to understand, predict and optimize materials, mainly for photocatalysis, energy conversion and storage. In these regards, we investigate phase stability, optical properties, excitons, and ionic diffusion; in close collaboration with experimental colleagues.[1,2,3,4,5,6,7,8]


