Research: Observation of a linked-loop quantumstate in a topological magnet

Various types of knots, links and windings are known in real objects that can have a fundamental explanation in knot theory in mathematics. On the other hand, new developing quantum topology also provides an insight powerful understanding of aforementioned geometries in term of topological invariants, which capture global information about the quantum state.  An international team of researchers directly visualized the mystery of linked loops of magnetic Co₂MnGa Heusler material by spectroscopic methods. They find that there are three loops belonging to three mirror planes, each linking with the other two exactly twice, giving the linking number (2, 2, 2) within knot theory. These findings motivate the application of knot theory as well as discover the unusual behaviour in many quantum magnets and superconductors.

I. Belopolski, G. Chang, T. A. Cochran, Z.-J. Cheng, X. P. Yang, C. Hugelmeyer, K. Manna, J.-X. Yin, G. Cheng, D. Multer, M. Litskevich, N. Shumiya, S. S. Zhang, C. Shekhar, N. B. M. Schröter, A. Chikina, C. Polley, B. Thiagarajan, M. Leandersson, J. Adell, S.-M. Huang, N. Yao, V. N. Strocov, C. Felser, M. Z. Hasan,
Observation of a linked-loop quantum state in a topological magnet,
Nature 604, 647–652 (2022) (arXiv)