Kagome metal

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Kagome metal is a ferromagnetic quantum material that is firstly used in literature in 2011 for a compound of Fe3Sn2.[1] However, this material have been created for several decades.[2] In this material, metal atoms are arranged in a lattice resembling the Japanese kagome basket weaving pattern. The same material has also been termed as "kagome magnet" since 2018.[3][4][5][6] Kagome metal (or magnets) refer to a new class of magnetic quantum materials hosting kagome lattice and topological band structure.[7] They include 3-1 materials (example: antiferromagnet Mn3Sn), 1-1 materials (example: paramagnet CoSn), 1-6-6 materials (example: ferrimagnet TbMn6Sn6), 3-2-2 materials (example: hard ferromagnet Co3Sn2S2), and 3-2 materials (example: soft ferromagnet Fe3Sn2), thus demonstrating a variety of crystal and magnetic structures. They generally feature a 3d transition metal based magnetic kagome lattice with an in-plane lattice constant ~5.5Å. Their 3d electrons dominate the low-energy electronic structure in these quantum materials, thus exhibiting electronic correlation. Crucially, the kagome lattice electrons generally feature Dirac band crossings and flat band, which are the source for nontrivial band topology. Moreover, they all contain the heavy element Sn, which can provide strong spin-orbit coupling to the system. Therefore, this is an ideal system to explore the rich interplay between geometry, correlation, and topology.

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".[8] 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.[8] Unlike superconductivity, this structure and behavior is stable at room temperature.[9] 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.[8] 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 Fe3Sn2 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.[9][10][11] These behaviors are promising for the development of technologies in quantum computing, spin superconductors, and low power electronics.[9][8] As of 2019, more Kagome materials displaying similar topology were being experimented with, such as in magnetically doped Weyl-Semimetals Co2MnGa and Co3Sn2S2.[12]

Development[]

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).[13]

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.[14] 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.[8]

The photo-electronic structure of this metal was mapped at Lawrence Berkeley National Lab's Advanced Light Source 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”.[9] A 30 meV gap between cones was shown, which is indicative of the Hall effect and massive Dirac fermions.[9]

The experiment was published in Nature on March 19, 2018.[8]

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.[11] 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.[15] This structure showed both massive Dirac fermions and electronic band structures where electrons do not occur.[15]

See also[]

Further reading[]

  • Ye, Linda; Kang, Mingu; Liu, Junwei; von Cube, Felix; Wicker, Christina R.; Suzuki, Takehito; Jozwiak, Chris; Bostwick, Aaron; Rotenberg, Eli; Bell, David C.; Fu, Liang; Comin, Riccardo; Checkelsky, Joseph G. (19 March 2018), "Massive Dirac fermions in a ferromagnetic kagome metal", Nature, 555 (7698): 638–642, arXiv:1709.10007, Bibcode:2018Natur.555..638Y, doi:10.1038/nature25987, PMID 29555992, S2CID 4470420

References[]

  1. ^ Kida, T (2011). "The giant anomalous Hall effect in the ferromagnet Fe3Sn2—a frustrated kagome metal". J. Phys.: Condens. Matter. 23 (11): 112205. arXiv:0911.0289. Bibcode:2011JPCM...23k2205K. doi:10.1088/0953-8984/23/11/112205. PMID 21358031.
  2. ^ Trumpy, G (1970). "Mössbauer-Effect Studies of Iron-Tin Alloys" (PDF). Physical Review B. 2 (9): 3477. Bibcode:1970PhRvB...2.3477T. doi:10.1103/PhysRevB.2.3477.
  3. ^ Yin, Jia-Xin (2018). "Giant and anisotropic many-body spin–orbit tunability in a strongly correlated kagome magnet". Nature. 562 (7725): 91–95. arXiv:1810.00218. Bibcode:2018Natur.562...91Y. doi:10.1038/s41586-018-0502-7. PMID 30209398. S2CID 205570556.
  4. ^ Li, Yangmu (2019). "Magnetic-Field Control of Topological Electronic Response near Room Temperature in Correlated Kagome Magnets". Physical Review Letters. 123 (19): 196604. arXiv:1907.04948. Bibcode:2019PhRvL.123s6604L. doi:10.1103/PhysRevLett.123.196604. PMID 31765205. S2CID 195886324.
  5. ^ Khadka, Durga (2020). "Anomalous Hall and Nernst effects in epitaxial films of topological kagome magnet Fe3Sn2". Physical Review Materials. 4 (8): 084203. arXiv:2008.02202. Bibcode:2020PhRvM...4h4203K. doi:10.1103/PhysRevMaterials.4.084203. S2CID 220968766.
  6. ^ Yin, Jia-Xin Yin (2021). "Probing topological quantum matter with scanning tunnelling microscopy". Nature Reviews Physics. 3 (4): 249–263. arXiv:2103.08646. Bibcode:2021NatRP...3..249Y. doi:10.1038/s42254-021-00293-7. S2CID 232240545.
  7. ^ Yin, Jia-Xin Yin (2021). "Probing topological quantum matter with scanning tunnelling microscopy". Nature Reviews Physics. 3 (4): 249–263. arXiv:2103.08646. Bibcode:2021NatRP...3..249Y. doi:10.1038/s42254-021-00293-7. S2CID 232240545.
  8. ^ Jump up to: a b c d e f Jennifer Chu (March 19, 2018), "Physicists discover new quantum electronic material", MIT News, Massachusetts Institute of Technology
  9. ^ Jump up to: a b c d e "The Electronic Structure of a "Kagome" Material". ALS. 2018-06-15. Retrieved 2020-04-17.
  10. ^ "A new 'spin' on kagome lattices". phys.org. Retrieved 2020-04-17.
  11. ^ Jump up to: a b Ye, Linda; Chan, Mun K.; McDonald, Ross D.; Graf, David; Kang, Mingu; Liu, Junwei; Suzuki, Takehito; Comin, Riccardo; Fu, Liang; Checkelsky, Joseph G. (2019-10-25). "de Haas-van Alphen effect of correlated Dirac states in kagome metal Fe 3 Sn 2". Nature Communications. 10 (1): 4870. arXiv:1809.11159. Bibcode:2019NatCo..10.4870Y. doi:10.1038/s41467-019-12822-1. ISSN 2041-1723. PMC 6814717. PMID 31653866.
  12. ^ "The best of two worlds: Magnetism and Weyl semimetals". phys.org. September 2019. Retrieved 2020-04-17.
  13. ^ Ye, Linda; Kang, Mingu; Liu, Junwei; von Cube, Felix; Wicker, Christina R.; Suzuki, Takehito; Jozwiak, Chris; Bostwick, Aaron; Rotenberg, Eli; Bell, David C.; Fu, Liang (19 March 2018). "Massive Dirac fermions in a ferromagnetic kagome metal". Nature. 555 (7698): 638–642. arXiv:1709.10007. Bibcode:2018Natur.555..638Y. doi:10.1038/nature25987. ISSN 1476-4687. PMID 29555992. S2CID 4470420.
  14. ^ Aristos Georgiou (March 20, 2018), "Kagome metal: new exotic quantum material developed by scientists", Newsweek
  15. ^ Jump up to: a b "MIT researchers realize "ideal" kagome metal electronic structure". MIT News. Retrieved 2020-04-17.
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