Composition-tuned Fermi level and anomalous Hall effect in epitaxial grown Mn(Bi1-xSbx)2Te4 thin films

Abstract

MnBi₂Te₄-based intrinsic magnetic topological insulators have attracted keen interest for many exotic quantum states, such as quantum anomalous Hall (QAH) insulator state and axion insulator state. Such intriguing quantum states have been extensively studied in the atomically thin flakes exfoliated from single crystals. Due to the advantages of thin film processes that facilitate large-scale fabrication and the control of film thickness, MnBi₂Te₄-based thin films could be indispensable for further pursuit of the QAH effect and for exploring other intriguing quantum states, but they urgently need further exploration. Here, we fabricate high-quality Mn(Bi_1-xSb_x)₂Te₄ (0 ≤ x ≤ 1) thin films by molecular beam epitaxy, and investigate the effect of Sb content on Fermi level, band topology and intrinsic magnetism. The angle-resolved photoemission spectroscopy and electrical transport measurements demonstrate a continuous transition from n-type to p-type can be realized by increasing Sb contents, while the Fermi level is close to the charge neutral point at x = 0.25. Mn(Bi_1-xSb_x)₂Te₄ films exhibit AH sign reversal and a transition of magnetic exchange interaction across x = 0.5, as a consequence of the topological phase transition induced by lifting Sb content. Furthermore, the promising MnBi_1.5Sb_0.5Te₄ film acquires the most remarkable AH signal among all films and presents robust spontaneous surface magnetization. Our results pave the way for exploring the QAH effect on the potential platform of MnBi_1.5Sb_0.5Te₄ films.