Single-Layer Magnet Phase in Intrinsic Magnetic Topological Insulators, [MnTe][Bi2Te3]n, Far beyond the Thermodynamic Limit

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Abstract
The intrinsic magnetic topological insulator (IMTI) family [MnTe][Bi2Te3]n has demonstrated magneto-topological properties dependent on n, making it a promising platform for advanced electronics and spintronics. However, due to technical barriers in sample synthesis, their properties in the large n limit remain unknown. To overcome this, we utilized the atomic layer-by-layer molecular beam epitaxy (ALL-MBE) technique and achieved IMTIs with n as large as 15, far beyond that previously reported in bulk crystals or thin films. Then, we discover that the "single-layer magnet (SLM)" phase, primarily determined by intralayer ferromagnetic coupling, emerges for n > ∼4 and remains little affected up to n = 15. Nonetheless, still, nonzero, interlayer ferromagnetic coupling is necessary to stabilize the SLM phase, suggesting that the SLM phase eventually disappears in the n → ∞ limit. This study uncovers the secrets of IMTIs beyond the thermodynamic limit and opens a door to diverse magneto-topological applications.
Funding Information
  • Multidisciplinary University Research Initiative (W911NF2020166)
  • Army Research Office (W911NF2010108)
  • Basic Energy Sciences (DE-SC0012704)

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