Study of Superconductor based Van Der Waals Heterostructures

Abstract

When two or more atomically thin, layered sheets (2D) of materials are placed on top of each other their properties change. These growing class of systems have strong in-plane covalent bonding and the atomically thin layers are attached to each other via weak Van Der Waals forces. Hence, they are referred to as Van Der Waals heterostructures. They have been explored quite a lot in recent years because of their experimental feasibility. One of the most common Van Der Waals heterostructures is graphite which is composed entirely of layered sheets of graphene. Graphene is formed of a 2D crystal of carbon atoms arranged in a honeycomb structure. Transition Metal Dichalcogenides (TMDs) also share the same type of honeycomb structure but in their monolayer, they are optically active (possess a direct band gap). In this report, we shall plot the energy dispersion for Graphene and TMDs by finding the Hamiltonian for them using mainly the Tight binding model. The second quantized formulation have been adopted throughout this calculation. Tight binding model have been briefly discussed in the first chapter itself. The Three band tight binding model used for the calculation of the effective Hamiltonian for the Transition metal Dichalcogenides have also been discussed very briefly. NbSe2 is a superconductor as the temperature is cooled below its Tc (critical temperature). As for the main objective of this dissertation, we shall find the energy band structure for Graphene+ NbSe2 system.