Study On Cooperative Modulation Of Spin-valley Polarized Transport By External Fields In Graphene-like Materials

In the past more than ten years,two-dimensional?2D?materials,represented by graphene,have become a research hotspot in the fields of condensed matter physics and materials science.Following graphene,other 2D hexagonal crystal materials have been emerging one after another,such as silicene and monolayer MoS₂.Because such 2D materials have the lattice structure like graphene,they can be referred to as graphene-like materials.Compared with graphene,graphene-like materials have significant differences in nature of the constituent atoms,valence-bond structure of real space and symmetry,which leads to different electronic properties.Based on the previous works,in this thesis we mainly focus on the cooperative modulation of spin-valley polarized transport by external fields in graphene-like materials.The results indicated that?1?quantum tunneling effect of massive Dirac fermions in silicene can be substantially influenced by an externally applied perpendicular electric field;?2?spin-and valley-selective transports of electrons in a normal/ferromagnetic/normal silicene tunnel junction can be accomplished by using the combined effect of perpendicular electric field,exchang field and circularly polarized light;?3?with the assistance of off-resonant circularly polarized light and ferromagnetic proximity effect,Spin-and valley-selective transport of electrons in a normal/ferromagnetic/normal MoS₂ tunnel junction can be realized only by adjusting the gate voltage;?4?tunnel magnetoresistance?TMR?effects and spin-valley filtering effects in a full magnetic junction of monolayer MoS₂ can be simultaneously achieved by the cooperative effects of off-resonant circularly polarized light,ferromagnetic proximity effect,and gate voltage.We think that the obtained results in the thesis will provide a theoretical basis for designing new spintronics and valleytronics devices with specific functions.