Magnctism And Dynamics Of Spin Hole Current In Doped Molybdenum Disulphide Monolayer

The rapid development of computer technology endows us with unprecedented computing power.We can use numerical simulation to solve the complicated physical system problems which have no analytical solution.Therefore,besides theoretical and experimental physics,computational physics has become a research tool helping us to understand and predict the law of motion in the physical universe.In the first chapter,we introduce two first principle calculation methods to solve the Schrodinger equation of many electrons in condensed matter systems,Hartree-Fock self-consistent field and density functional theory.We emphatically introduce the application of density functional theory in the magnetic and periodic systems.In the second chapter,we introduce two frequently used nonadiabatic molecular dynamics simulation methods to solve the time-dependent Schrodinger equation in the mixed quantum-classical dynamics frame.We emphatically introduce the fewest-switches surface hopping and its procedure realization.We use the research methods in the first two chapters to predict the possibility of inducing magnetism and spin current in the molybdenum disulphide monolayer by doping with 3d transition metals.In the third chapter,we introduce the results of calculating the magnetic moments and magnetic orders of the impurity defects using the spin-polarized density functional theory.For the first time,we comprehensively investigate the underlying mechanism of the magnetism and discover that robust ferromagnetic order can be built in molybdenum disulphide monolayer doped with chromium and copper.With further consideration for the on-site Coulomb interaction,we find that a particular chromium superlattice holds the promise of a room temperature dilute magnetic semiconductor.In the fourth chapter,we for the first time predict that fully spin-polarized hole current can be generated in molybdenum disulphide monolayer doped with copper.We perform an ab initio nonadiabatic molecular dynamics investigation to study the dynamics of the spin hole current.Our results show that the initial hole generation and environmental temperature are two key factors determining the lifetime of the photo-generated spin hole current.A longer lifetime for the spin hole current can be obtained by generating holes on the lower edge of the impurity states,or by decreasing the temperature.Our results provide valuable insights into the design of materials and devices for spintronics.In the fifth chapter,we summarize the findings and limitations in this research,and we make prospects for the research developments in the future.