Fabricating a hexagonal FeTe monolayer with a moiré superlattice on topological insulator Bi2Te3

The growth of a hexagonal FeTe (alpha-FeTe) thin layer on three-dimensional topological insulator Bi2Te3 has been systematically investigated by combining scanning tunneling microscopy/spectroscopy (STM/STS) with density-functional theory (DFT) calculations. Through post-annealing at 560 K after room-temperature deposition of Fe onto Bi2Te3, alpha-FeTe has been fabricated with an atomic lattice constant of 4.0 +/- 0.1 & Aring;, which is much smaller than the 4.4 +/- 0.1 & Aring; of the Te-terminated Bi2Te3 surface. The lattice mismatch and a sufficiently large FeTe-Bi2Te3 distance give rise to a moir & eacute; pattern with a periodicity of 6.0 +/- 0.1 nm, corresponding to a p(15 x 15) superlattice. On the other hand, an enhanced projected density of states (PDOS) is found at about -0.8 eV and +1.4 eV of alpha-FeTe/Bi2Te3 in the tunneling spectra. These enhancements, as interpreted from the DFT calculation, arise from the contribution of the 3d out-of-plane orbitals in Fe. DFT calculations also reveal nonzero net magnetization and indicate ferromagnetic (FM) order in the system - contrasting the well-studied bicollinear antiferromagnetism in beta-FeTe/Bi2Te3. To summarize, our successful fabrication of alpha-FeTe/Bi2Te3 provides a distinct platform from beta-FeTe/Bi2Te3, enabling an exploration of the interplay between magnetism and interface-induced superconductivity.