二维过渡金属硫化物中Rashba自旋轨道耦合效应的电场调控研究

摘要 本文采用基于密度泛函理论的第一性原理计算方法，对6种二维过渡金属硫化物MX2（M=Mo，W；X=S，Se，Te）中的Rashba自旋轨道耦合效应进行了系统研究.对6种MX2材料施加垂直方向电场，发现阴离子X对于电场诱导的Rashba自旋轨道耦合效应起主要作用：X原子序数越大，电场诱导的Rashba劈裂也越大；阳离子M被阴离子X覆盖，对电场诱导的Rashba自旋劈裂影响较弱.因此，6种MX2单层的Rashba自旋劈裂大小依次为：WTe2 > MoTe2 > WSe2 > MoSe2 > WS2 > MoS2.施加电场后，从布里渊区中心Γ点到布里渊区边界K/K'点，自旋方向二维平面内转向垂直方向，并且随着电场的增加，面内自旋成分逐渐增加.
Abstract：Using the first-principles density functional theory calculations, we investigate the Rashba spin-orbit coupling of the transition metal dichalcogenide (TMD) monolayers MX2(M=Mo, W; X=S, Se, Te) induced by the external electric field. It is found that the anions X play an important role on the Rashba spin-orbit coupling effect. With the increase of the atomic number of X, Rashba spin-orbit splitting around the Γ point increases more distinctively, and the external electric field can hardly influence the cations because of the coverage by the anions. Thus the strength of the Rashba spin-orbit coupling follows the sequence:WTe2 > MoTe2 > WSe2 > MoSe2 > WS2 > MoS2. Furthermore, the distribution of the spin polarization along the high symmetry line Γ-K/K' turns from the vertical direction to the two-dimensional plane under the external electric fields, and the in-plane spin polarization distribution rises with the increase of the external electric field.