Weyl Electron-Mediated Spiral Spin Order in a Topological Magnet

August 28, 2023
Weyl Electron-Mediated Spiral Spin Order in a Topological Magnet
(left) Neutron diffraction along the (HH8) direction in SmAlSi, which reveals a temperature-dependent Bragg peak at Q = (1/3 - , 1/3 - , 8). (right) 3D rendition of one possible spin structure for SmAlSi.

Scientific Achievement

Exotic spiral magnetic order is discovered in the semimetal SmAlSi and is the result of strong coupling between topological Weyl electrons and nearly-isotropic Sm3+ local moments.

Significance and Impact

This work shows that topological quasiparticles, including Weyl fermions, can mediate magnetic interactions and help stabilize complex magnetic ordering and skyrmion phases that are in great demand for high-density and high-speed magnetic memory devices.

Research Details

  • Elastic neutron scattering, heat capacity, magnetization and hall effect measurements were combined with electronic structure calculations to understand Weyl electron-mediated spiral magnetism in SmAlSi.
  • The 3x flux increase from the recent upgrade of HB-1A enabled measurement of weak magnetic signals in a highly-absorbing SmAlSi single crystal with no isotope enrichment.

“Large Topological Hall Effect and Spiral Magnetic Order in the Weyl Semimetal SmAlSi”
Xiaohan Yao, Jonathan Gaudet, Rahul Verma, David Graf, Hung-Yu Yang, Faranak Bahrami, Ruiqi Zhang, Adam Aczel, Sujan Subedi, Darius Torchinsky, Jianwei Sun, Arun Bansil, Shin-Ming Huang, Bahadur Singh, Peter Blaha, Predrag Nikolić, and Fazel Tafti,
Physical Review X 13, 011035 (2023). DOI: https://doi.org/10.1103/PhysRevX.13.011035