Role of intrinsic defects in the Dirac point gap of MnBi2Te4 antiferromagnetic topological insulator

The different degree of the defectness of the MnBi2Te4 crystals has been proposed to be behind the contradictory reports concerning the absence/presence of the Dirac point gap in the topological surface state. In this proposal, we aim at probing the magnetic properties of 2D layered MnBi2Te4. Specifically, by XAS-XMCD experiments at Mn-L2,3 edge we will check that the magnetic moment of Mn at surface will decrease linearly as the substitution number of Mn in the Bi layers increases. In addition, we will study and quantify the antiferromagnetic coupling between the Mn atoms in the Mn- and Bi-layers. The outcomes from the planned experiments will complement our laboratory STM and ARPES measurements pointing to a crucial role of the Mn’s substitutions
in determining the magnetic gap at Dirac point as function of the (Mn, Bi) concentration.