Spin Transport In Low-Dimensional Materials: A Study From First Principle Electronic Structure Calculations

Abstract

Conventional storage and processing devices based on the electrons’ charge trans- port mechanisms are insufficient to meet the needs of the future. Spintronics, in which the electron’s spin degree of freedom has also been exploited along with its charge, can be considered an alternative to charge-based technology. Storage and processing devices based on spin transport can overcome the limitations of charge-based transport devices and can provide many additional device function- alities. Two-dimensional (2D) materials are considered a suitable medium for spin transport. This thesis mainly focused on spin transport in 2D materials. Herein, the electronic structure and magnetic properties of various 2D materials have been thoroughly investigated using first-principle calculations. Magnetic metal-2D ma- terial interfaces are constructed and the possibility of spin injection/scattering has been carefully studied at the interface. Two probe magnetic junctions are modeled by combining different 2D materials and metals, where 2D materials are sandwiched between two magnetic electrodes. Spin-transport properties are investigated through magnetic junctions by performing a combined study of den- sity functional theory (DFT) and nonequilibrium Green’s function (NEGF) meth- ods. The transmission spectrum, current-voltage characteristics, spin injection efficiency, and magnetoresistance are calculated for different modeled devices at various bias voltages in the parallel and anti-parallel electrodes magnetic config- urations. Overall, this work provides a better understanding of spin injection at the metal-2D material interface. The reported results in this thesis could be suit- able guidelines for the development of future spintronic devices based on TMDC materials.