Magnetic Properties and Electronic Structure of Magnetic Topological Insulator MnBi2Se4
Abstract
The intrinsic magnetic topological insulators MnBi2X4 (X = Se, Te) are promising candidates in realizing various novel topological states related to symmetry breaking by magnetic order. Although much progress had been made in MnBi2Te4, the study of MnBi2Se4 has been lacking due to the difficulty of material synthesis of the desired trigonal phase. Here, we report the synthesis of multilayer trigonal MnBi2Se4 with alternating-layer molecular beam epitaxy. Atomic-resolution scanning transmission electron microscopy (STEM) and scanning tunneling microscopy (STM) identify a well-ordered multilayer van der Waals (vdW) crystal with septuple-layer base units in agreement with the trigonal structure. Systematic thickness-dependent magnetometry studies illustrate the layered antiferromagnetic ordering as predicted by theory. Angle-resolved photoemission spectroscopy (ARPES) reveals the gapless Dirac-like surface state of MnBi2Se4, which demonstrates that MnBi2Se4 is a topological insulator above the magnetic ordering temperature. These systematic studies show that MnBi2Se4 is a promising candidate for exploring the rich topological phases of layered antiferromagnetic topological insulators.