User:ScooterR04/sandbox

Kagome metal is a ferromagnetic quantum material created in 2018. In the material, metal atoms are arranged in a lattice resembling the Japanese kagome basket weaving pattern. The material was announced in Nature in March 2018 by investigators from Massachusetts Institute of Technology, Harvard University, and Lawrence Berkeley National Laboratory, all in the United States.

In the Kagome structure, atoms are arranged into layered sets of overlapping triangles so that there exist large empty hexagonal spaces. Electrons in the metal experience a “three-dimensional cousin of the quantum Hall effect”. The inherent magnetism of the metal and the quantum-mechanical magnetism induce electrons to flow around the edges of the triangular crystals, akin to superconductivity. Unlike superconductivity, this structure and behavior is stable at room temperature. Other structures were shown to exhibit the quantum hall effect at very low temperatures with an external magnetic field as high as 1 million times the strength that of the earth. By building metal out of a ferromagnetic material, that exterior magnetic field was no longer necessary, and the quantum Hall effect persists into room temperature.

The Kagome alloy synthesized in 2018 displayed several exotic quantum electronic behaviors that add to its quantum topology. The lattice harbors massive Dirac Fermions, Berry curvature, band gaps, and spin-orbit activity, all of which are conducive to the Hall Effect and zero energy loss electric currents. These behaviors are promising for the development of technologies in quantum computing, spin superconductors, and low power electronics. Today, more Kagome materials are being experimented with that display similar topology, such as in magnetically doped Weyl-Semimetals Co2MnGa and Co3Sn2S2.

March 2018 Experiment
The experiment published in Nature was led by Linda Ye and Mingu Kang from the Massachusetts Institute of Technology Department of Physics. The other researches published in the article were: Junwei Liu (MIT), Felix von Cube (Harvard), Christina R. Wicker (MIT), Takehito Suzuki (MIT), Chris Jozwiak (Berkeley Labs), Aaron Bostwick (Berkeley Labs), Eli Rotenberg (Berkeley Labs), David C. Bell (Harvard), Liang Fu (MIT), Riccardo Comin (MIT), and Joseph G. Checkelsky (MIT).

The team constructed a Kagome lattice using an iron and tin alloy Fe3Sn2. When Fe3Sn2 is heated to about 750℃ (1380°F), the alloy naturally assumes a Kagome lattice structure. To maintain this structure at room temperature, the team cooled it in an ice bath. The resulting structure had iron atoms at the corners of each triangle surrounding tin atoms, the tin atoms stabilizing the large empty hexagonal space.

The photo-electronic structure of this metal was mapped at Berkeley ALS Beamlines 7.0.2 MAESTRO and 4.0.3 MERLIN. The measurements taken here mapped the band structures of the metal under a current and showed “the double-Dirac-cone structure corresponding to Dirac Fermions”. A 30 meV gap between cones was shown, which is indicative of the Hall effect and massive Dirac Fermions.

The experiment was published in Nature on March 19, 2018.

Expansions Upon the 2018 Experiment
Linda Ye and the rest of the MIT team continued working with the kagome metal, looking into more properties on Fe3Sn2 and other iron-tin alloys. According to an article published by the team on October 25, 2019 in Nature Communications, the lattice was shown to exhibit spin-orbit coupling de Haas van Alphen oscillations and Fermi surfaces. The team also continued to modify the structure of the metal, and in an article published in Nature Materials on December 9, 2019, they found that FeSn in a 1 to 1 ratio exhibited a more “ideal” lattice. The two-dimensional layers with iron and tin in the kagome shape were separated by a layer entirely of tin, allowing them to have separate band structures. This structure showed both massive Dirac fermions and electronic band structures where electrons do not occur.