Experimental and theoretical investigations On the undoped and doped bsts compounds and Gadolinium carbon co doped Gallium nitride

Abstract

Topological Insulators (TI), a fourth paradigm of matter apart from insulator, semiconductor and conductors, is being extensively investigated in the past few decades owing to their application in various fields. Their surface states are conducting while in the bulk state, they exhibit insulator behavior, hence the name topological insulator. They have unique properties in which electrons behaves like photons leading to enhancement in the property of semiconductor devices. The spin of the electrons on the surface states and internal insulation in bulk of TIs contributes to low power dissipation in TI devices. The surface electrons possess spin-polarized structure leading to the contribution of study of spintronics and magnetic devices. Furthermore, the surface states of TIs, are not affected by slight perturbations and therefore TIs are the best material for the application of quantum computation and artificial intelligence. To utilize TI materials for real applications, ease of synthesis of these materials, and the theoretical and experimental understanding of structural, electronic and magnetic properties are important. Electronic and optical properties of the bulk and primitive A2B3 (A = Bi and Sb and B = Se and Te) compound structure has been investigated using the density functional theory based on the full potential linear augmented plane wave method via inclusion of spin orbit coupling (SOC) with GGA-PBE Trans-Blaha modified Becke-Johnson (TB_mBJ) potential. The total energy calculations show the direct band nature of all the compounds which is confirmed by the presence of chalcogens p-states in the valence band maximum (VBM) and pnictogen p-states in the conduction band minimum (CBM) at and#915;-point. The fundamental electronic band gap values calculated are close to the experimental values. The inclusion of spin effects of electron by spin orbit coupling (SOC) has brought about band bending in the density of states (DOS) proving the topological nature of the compounds. newline newline newline