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Hidden Local Symmetry Breaking for Understanding the Peculiar Magnetism in Co3Sn2S2

January 31, 2023

Scientific Achievement

It is seen that the onset of ferromagnetic order in the Kagome-lattice magnetic Weyl semi-metal Co3Sn2S2 is accompanied by a broken local symmetry describable as a rhombohedral to monoclinic distortion.

(Left) Contour plot of the pair distribution functions patterns vs temperature. Co-emergence of the new peaks in marked by arrows and weak ferromagnetic peak (110) at TC. (Right) Anisotropic atomic displacements between Co1 and Co2 atoms of the kagome lattice.

Significance and Impact

Co3Sn2S2 exhibits global rhombohedral symmetry, but local distortions lead to the formation of a low temperature spin glass state despite the absence of lattice or site disorder; similar local symmetry breaking could be the key to understanding unusual magnetic and electronic ground states of other topological materials.

Research Details

  • Average ferromagnetic order and moment were identified with half-polarized neutron diffraction measurements.
  • Average and local crystal structures were determined by both conventional powder neutron diffraction and total scattering measurements.
  • Density functional theory calculations unveils the effect of the local symmetry breaking on the local ferromagnetic instability and Weyl physics.

Related Publication: Zhang, Q. et. al. (2022). Hidden Local Symmetry Breaking in a Kagome-Lattice Magnetic Weyl Semimetal. Journal of the American Chemical Society, 144, 14339-14350.