Synthesis, 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.

Emergent Phenomena in Magnetic Two-Dimensional Materials and van der Waals Heterostructures

“…Recently, MnBi 2 Se 4 thin films have been grown using molecular beam epitaxy . The theoretical calculations reveal that MnBi 2 Se 4 is a magnetic insulator, with FM septuple layers stacking in the AFM coupling approach, in agreement with the experimental observations below ∼10 K . Different from the predicted out-of-plane magnetic anisotropy, the experiment reports the in-plane magnetism of MnBi 2 Se 4 , which is caused by dipole–dipole interaction .…”

Formation of a Stable Surface Oxide in MnBi2Te4 Thin Films

“…Growth of MnBi 2 Te 4 on α-Al 2 O 3 (0001) utilizes a two-step growth method, by modifying a recipe for ultrathin Bi 2 Te 3 /Bi 2 Se 3 or MnBi 2 Se 4 grown on sapphire. 12 Atomically flat sapphire substrates (Shinkosha Japan) were annealed in UHV at 600 °C to outgas for an hour before annealing up to 800 °C for 20 min to produce the (1 × 1) surface reconstruction of clean sapphire. An initial seeding layer of 1quintuple layer (QL) of Bi 2 Te 3 was grown at 150 °C to aid nucleation.…”

Colloquium: Quantum anomalous Hall effect

“…12(a)]. As noted in Sec.II.B, MnBi 2 Te 4 is one member of the Mn(Bi/Sb) 2n (Se/Te) 3n+1 family of compounds, which includes MnBi 4 Te 7 (Ding et al, 2020;Hu et al, 2020b;Klimovskikh et al, 2020;Li et al, 2019a;Shi et al, 2019;Vidal et al, 2019b;Wu et al, 2019b;Xu et al, 2020a;Yan et al, 2020), MnBi 6 Te 10 (Jo et al, 2020; Klimovskikh et al, 2020;Li et al, 2019a;Shi et al, 2019;Tian et al, 2020;Yan et al, 2020), MnBi 8 Te 13 (Hu et al, 2020a), MnSb 2 Te 4 (Chen et al, 2020b;Ge et al, 2021;Liu et al, 2021c;Murakami et al, 2019;Wimmer et al, 2021;Yan et al, 2021cYan et al, , 2019a, MnSb 4 Te 7 (Huan et al, 2021), Mn(Bi,Sb) 2 Te 4 (Chen et al, 2019a(Chen et al, , 2020bJiang et al, 2021;Lee et al, 2021;Yan et al, 2019a), and MnBi 2 Se 4 (Zhu et al, 2021). Mn(Bi/Sb) 2n (Se/Te) 3n+1 can be viewed as (n-1) (Bi/Sb) 2 (Se/Te) 3 QLs stacked on a Mn(Bi/Sb) 2 (Se/Te) 4 parent to form one unit cell.…”