Mapping Dirac fermions in the intrinsic antiferromagnetic topological insulators 
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Liang, Zuowei; Luo, Aiyun; Shi, Mengzhu; Zhang, Qiang; Nie, Simin; Ying, Jianjun; He, Junfeng; Wu, Tao; Wang, Zhijun; Xu, Gang; Wang, Zhenyu; Chen, X.-H.

doi:10.1103/physrevb.102.161115

Cited by 35 publications

(14 citation statements)

References 55 publications

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“…Therefore the type A defects can be identified with the Bi Te antisites, similarly to what happens in Bi 2 Te 3 TI 63 , where they also appear as bright protrusions for both bias polarities. This conclusion is in line with previous STM studies of MnBi 2 Te 4 (0001) 13,61,62,64 .…”

Section: Figure 1dsupporting

confidence: 93%

“…Thus, we attribute the triangular-shaped depressions to the Mn Bi substitutions in the subsurface layer. Similar features have been previously observed in STM for magnetically doped Bi 2 Se 3 -family TIs [58][59][60] and, recently, for MnBi 2 Te 4 (0001) 13,61,62 . Besides, the existence of Mn Bi defects has also been claimed recently based on the electron energy loss spectroscopy and transmission electron microscopy analysis 55 .…”

Section: Figure 1dsupporting

confidence: 87%

“…The latter means that, apart from the second (subsurface) layer, Mn Bi atoms should also occur in the sixth layer counting from the surface, while Bi atoms, in turn, should occupy Mn positions (Bi Mn ) in the fourth layer. However, no clear signatures of the defects lying below the second atomic layer have been observed on the STM topographic images so far 13,61,62,64 . As far as the spectroscopic dI/dV imaging is concerned, apart from the above discussed deep-lying defects (Supplementary Fig.…”

Section: Figure 1dmentioning

confidence: 94%

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Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

Garnica¹,

Otrokov²,

Aguilar³

et al. 2021

Preprint

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The Dirac point gap at the surface of the antiferromagnetic topological insulator MnBi2Te4 is a highly debated issue. While the early photoemission measurements reported on large gaps in agreement with theoretical predictions, other experiments found vanishingly small splitting of the MnBi2Te4 Dirac cone. Here, we study the crystalline and electronic structure of MnBi2Te4(0001) using scanning tunneling microscopy/spectroscopy (STM/S), micro(µ)-laser angle resolved photoemission spectroscopy (ARPES), and density functional theory (DFT) calculations. Our topographic STM images clearly reveal features corresponding to point defects in the surface Te and subsurface Bi layers that we identify with the aid of STM simulations as BiTe antisites (Bi atoms at the Te sites) and MnBi substitutions (Mn atoms at the Bi sites), respectively. X-ray diffraction (XRD) experiments further evidence the presence of cation (Mn-Bi) intermixing. Altogether, this affects the distribution of the Mn atoms, which, inevitably, leads to a deviation of the MnBi2Te4 magnetic structure from that predicted for the ideal crystal structure. Our transport measurements suggest that the degree of this deviation varies from sample to sample. Consistently, the ARPES/STS experiments reveal that the Dirac point gap of the topological surface state is different for different samples/sample cleavages. Our DFT surface electronic structure calculations show that, due to the predominant localization of the topological surface state near the Bi layers, MnBi defects can cause a strong reduction of the MnBi2Te4 Dirac point gap, given the recently proved antiparallel alignment of the MnBi moments with respect to those of the Mn layer. Our results provide a key to puzzle out the MnBi2Te4 Dirac point gap mystery.

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Section: Figure 1dsupporting

confidence: 93%

Section: Figure 1dsupporting

confidence: 87%

Section: Figure 1dmentioning

confidence: 94%

See 1 more Smart Citation

Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

Garnica¹,

Otrokov²,

Aguilar³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…For φ = 0.5 and TG = 410 °C, the surface showed randomly oriented elongated structures, which might be due to the formation of a Mn-rich phase; its rms roughness was 3.85 nm. The STM result revealed that the hexagonal atomic structure on the surface is consistent with the imaging of the topmost Te layer [46,47]; the in-plane lattice parameter was 4.0 Å, as shown in Figure 2f. These structural features confirmed by the AFM and XRD reveal the high quality of the pure MnBi2Te4 films grown by the delicate MBE method.…”

Section: Surface Morphologysupporting

confidence: 71%

“…The layering step is distinguishable on the enlarged surface shown in Figure 2e. The step height is ~1.4 nm (inset of Figure 2e), which is the same as the height of a single SL of MnBi2Te4 [25,46]. For φ = 0.5 and TG = 410 °C, the surface showed randomly oriented elongated structures, which might be due to the formation of a Mn-rich phase; its rms roughness was 3.85 nm.…”

Section: Surface Morphologymentioning

confidence: 64%

Epitaxial Growth and Structural Characterizations of MnBi2Te4 Thin Films in Nanoscale

Chang

Chuang

et al. 2021

Nanomaterials

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The intrinsic magnetic topological insulator MnBi2Te4 has attracted much attention due to its special magnetic and topological properties. To date, most reports have focused on bulk or flake samples. For material integration and device applications, the epitaxial growth of MnBi2Te4 film in nanoscale is more important but challenging. Here, we report the growth of self-regulated MnBi2Te4 films by the molecular beam epitaxy. By tuning the substrate temperature to the optimal temperature for the growth surface, the stoichiometry of MnBi2Te4 becomes sensitive to the Mn/Bi flux ratio. Excessive and deficient Mn resulted in the formation of a MnTe and Bi2Te3 phase, respectively. The magnetic measurement of the 7 SL MnBi2Te4 film probed by the superconducting quantum interference device (SQUID) shows that the antiferromagnetic order occurring at the Néel temperature 22 K is accompanied by an anomalous magnetic hysteresis loop along the c-axis. The band structure measured by angle-resolved photoemission spectroscopy (ARPES) at 80 K reveals a Dirac-like surface state, which indicates that MnBi2Te4 has topological insulator properties in the paramagnetic phase. Our work demonstrates the key growth parameters for the design and optimization of the synthesis of nanoscale MnBi2Te4 films, which are of great significance for fundamental research and device applications involving antiferromagnetic topological insulators.

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Three-Dirac-fermion approach to unexpected universal gapless surface states in van der Waals magnetic topological insulators

Wang¹,

Wang²,

Xing³

et al. 2023

Sci. China Phys. Mech. Astron.

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Layered van der Waals (vdW) topological materials, especially the recently discovered MnBi2Te4-family magnetic topological insulators (TIs), have aroused great attention. However, there has been a serious debate about whether the surface states are gapped or gapless for antiferromagnetic (AFM) TI MnBi2Te4, which is crucial to the prospect of various magnetic topological phenomena. Here, a minimal three-Dirac-fermion approach is developed to generally describe topological surface states of nonmagnetic/magnetic vdW TIs under the modulation of the interlayer vdW gap. In particular, this approach is applied to address the controversial issues concerning the surface states of vdW AFM TIs. Remarkably, topologically protected gapless Dirac-cone surface states are found to arise due to a small expansion of the interlayer vdW gap on the surface, when the Chern number equals zero for the surface ferromagnetic layer; while the surface states remain gapped in all other cases. These results are further confirmed by our first-principles calculations on AFM TI MnBi2Te4. The theorectically discovered gapless Dirac-cone states provide a unique mechanism for understanding the puzzle of the experimentally observed gapless surface states in MnBi2Te4. This work also provides a promising way for experiments to realize the intrinsic magnetic quantum anomalous Hall effect in MnBi2Te4 films with a large energy gap.

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Mapping Dirac fermions in the intrinsic antiferromagnetic topological insulators (MnBi2Te4)(Bi2Te3

Cited by 35 publications

References 55 publications

Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

Native point defects and their implications for the Dirac point gap at MnBi$_2$Te$_4$(0001)

Epitaxial Growth and Structural Characterizations of MnBi2Te4 Thin Films in Nanoscale

Three-Dirac-fermion approach to unexpected universal gapless surface states in van der Waals magnetic topological insulators

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