Kagome-lattices of 3d-transition metals hosting Weyl/Dirac fermions and topological flat bands exhibit non-trivial topological characters and novel quantum phases, such as the anomalous Hall effect and fractional quantum Hall effect. With consideration of spin–orbit coupling and electron correlation, several instabilities could be induced. The typical characters of the electronic structure of a kagome lattice, i.e., the saddle point, Dirac-cone, and flat band, around the Fermi energy (EF) remain elusive in magnetic kagome materials. We present the experimental observation of the complete features in ferromagnetic kagome layers of YMn6Sn6 helically coupled along the c-axis, by using angle-resolved photoemission spectroscopy and band structure calculations. We demonstrate a Dirac dispersion near EF, which is predicted by spin-polarized theoretical calculations, carries an intrinsic Berry curvature and contributes to the anomalous Hall effect in transport measurements. In addition, a flat band and a saddle point with a high density of states near EF are observed. These multi-sets of kagome features are of orbital-selective origin and could cause multi-orbital magnetism. The Dirac fermion, flat band and saddle point in the vicinity of EF open an opportunity in manipulating the topological properties in magnetic materials.

2D materials have been widely applied in flexible electronics but only with limited stretchability, because the metal‐halide bonding is so strong that the materials’ electronic properties will be severely influenced upon tensile strain. Here, a strategy is proposed for the fabrication of ultrastretchable MoS2 photoreceptors based on chemical vapor deposition‐grown or manually stacked multilayer MoS2. Strain‐dependent spectroscopic comparisons of multilayer versus monolayer MoS2 indicate that the strain transfer is suppressed from bottom to top layers owing to interlayer sliding, which is consistent with the density functional theory and molecular dynamics simulations. Thus, the optoelectronic properties of multilayer MoS2 can withstand larger mechanical strain than monolayer MoS2. Leveraging this mechanical feature, ten‐layer MoS2 photodetector is fabricated on polystyrene‐b‐poly (ethylene‐co‐butylene)‐b‐polystyrene elastomer, withstanding ≈50% tensile strain and presenting 32 times higher photoresponsivity than that of monolayer MoS2 under the same stretching condition. Based on large‐area bilayer MoS2 film, 5 × 5 stretchable photodetector array is demonstrated and is capable of working as artificial photoreceptors to control a robotic hand under 16% tensile strain, showing great potential in applications for 2D material‐based electronic skin.

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Kagome-lattice of 3d-transition metals hosting Weyl/Dirac fermions and topological flat bands exhibit non-trivial topological characters and novel quantum phases, such as anomalous Hall effect and fractional quantum Hall effect. With consideration of spin-orbit coupling and electron correlation, several instabilities could be induced. The complete characters of the electronic structure of kagome lattice, i.e. the saddle point, Dirac-cone, and flat band, around the Fermi energy (EF) remain elusive in magnetic kagome materials. We present the first experimental observation of the complete features in ferromagnetic kagome layers of YMn6Sn6 helically coupled along the c-axis, by using angle-resolved photoemission spectroscopy and band structure calculations. We demonstrate a Dirac dispersion near EF arising from a spin-polarized orbital, which carries an intrinsic Berry curvature and contributes to the anomalous Hall effect in transport measurements. In addition, a flat band and a saddle point with a high density of states and with orbital-selective characters near EF are observed. These multi-orbital kagome features could cause multi-orbital magnetism. The Dirac fermion, flat band and saddle point in the vicinity of EF open an opportunity in manipulating the topological properties in magnetic materials.

A theoretical investigation on the structural stability, electronic, vibrational, and thermodynamic properties of the strontium apatites Sr10(PO4)6X2 (X = F, Cl, Br) is systematically conducted by the first-principles calculations.