First principles investigation of the spin orbit coupling driven quantum phases in Iridates

Abstract

Spin-orbit coupling (SOC) is an important intrinsic energy scale in quantum materials. Despite enormous efforts, there is some ambiguity in comprehending the diversified impact of SOC at the microscopic scale. In this thesis, we discuss the effect of SOC from the electronic structure and magnetism perspective using state of art density functional theory. Owing to its relative position in the periodic table, Iridates are known to lie in the strong SOC regime. However, our work on Iridates depicts that a material-specific understanding is crucial as it encompasses a multitude of rich quantum phases. We study a Fe-Ir based double perovskite series, which is investigated to understand the evolution of electronic and magnetic properties. We analyze the reason behind the difference in the experimental magnetic transition temperature and the relative effect of SOC on the end compounds of this series. We also examine three members of the hexagonal Iridates family which differ only in the occupation of the non-magnetic site. Nevertheless, we obtain that the impact of SOC is significantly different which is due to the renormalization of various energy scales. Further, we report a unique Iridate oxide that occurs in an isolated and layered square planar environment. Our investigations are crucial to understanding the structure-property relationship of this material and the nature of magnetism. Our work on the half-Heusler system demonstrates how we can modulate the SOC strength via chemical doping of Iridium that directly impacts the intrinsic part of the anomalous hall conductivity. Finally, we construct heterostructures by layering double perovskites and study the evolution of the structural, electronic, magnetic, and transport properties and the impact of SOC in a heterostructure environment for Iridates. newline