Visualization of Tunable Weyl Line in A–A Stacking Kagome Magnets

Abstract

Kagome magnets provide a fascinating platform for a plethora of topological quantum phenomena, in which the delicate interplay between frustrated crystal structure, magnetization, and spin–orbit coupling (SOC) can engender highly tunable topological states. Here, utilizing angle‐resolved photoemission spectroscopy, the Weyl lines are directly visualized with strong out‐of‐plane dispersion in the A–A stacked kagome magnet GdMn6Sn6. Remarkably, the Weyl lines exhibit a strong magnetization‐direction‐tunable SOC gap and binding energy tunability after substituting Gd with Tb and Li, respectively. These results not only illustrate the magnetization direction and valence counting as efficient tuning knobs for realizing and controlling distinct 3D topological phases, but also demonstrate AMn6Sn6 (A = rare earth, or Li, Mg, or Ca) as a versatile material family for exploring diverse emergent topological quantum responses.

Quantum interactions in topological R166 kagome magnet

“…Due to the in-plane FM order of the Mn kagome lattice, the Chern gap in the parental GdMn 6 Sn 6 should vanish, which is verified in first-principle calculations [84,85,144,147] where the Dirac point formed by electronlike band 40 meV below the Fermi level possesses a neglecting SOC gap (<0.5 meV). It is suggested such a small SOC gap is due to the remarkable cooperative interplay between the Kane-Mele SOC, low site symmetry and in-plane magnetic order [144]. The ARPES experiments found that upon 20% substitutional Tb doping (Tb 0.2 Gd 0.8 Mn 6 Sn 6 ), a significant band gap (25 meV) opens at this Dirac cone (figure 5(c)) as long as the magnetic reorientation to the out-of-plane easy axis occurs [144].…”

“…The studies on RMn 6 Sn 6 unveiled that the R atoms play an important role in the topological band structures while the substitution of the R atoms can effectively tune the topological band. Substituting Gd with Tb in alloy Tb x Gd 1−x Mn 6 Sn 6 smoothly tunes the magnetic anisotropy from in-plane to outof-plane FiM without introducing impurity on Mn kagome layer [144,146]. Due to the in-plane FM order of the Mn kagome lattice, the Chern gap in the parental GdMn 6 Sn 6 should vanish, which is verified in first-principle calculations [84,85,144,147] where the Dirac point formed by electronlike band 40 meV below the Fermi level possesses a neglecting SOC gap (<0.5 meV).…”

“…Substituting Gd with Tb in alloy Tb x Gd 1−x Mn 6 Sn 6 smoothly tunes the magnetic anisotropy from in-plane to outof-plane FiM without introducing impurity on Mn kagome layer [144,146]. Due to the in-plane FM order of the Mn kagome lattice, the Chern gap in the parental GdMn 6 Sn 6 should vanish, which is verified in first-principle calculations [84,85,144,147] where the Dirac point formed by electronlike band 40 meV below the Fermi level possesses a neglecting SOC gap (<0.5 meV). It is suggested such a small SOC gap is due to the remarkable cooperative interplay between the Kane-Mele SOC, low site symmetry and in-plane magnetic order [144].…”

“…It is suggested such a small SOC gap is due to the remarkable cooperative interplay between the Kane-Mele SOC, low site symmetry and in-plane magnetic order [144]. The ARPES experiments found that upon 20% substitutional Tb doping (Tb 0.2 Gd 0.8 Mn 6 Sn 6 ), a significant band gap (25 meV) opens at this Dirac cone (figure 5(c)) as long as the magnetic reorientation to the out-of-plane easy axis occurs [144].…”

Observation of Kondo lattice and Kondo-enhanced anomalous Hall effect in an itinerant ferromagnet

“…. In weakly interacting systems, the nodal lines can serve as strong sources of the Berry curvature and lead to large intrinsic AHE when the crossings are close to E F [38][39][40][41][42] . Recent theories have shown that the same logic can also be applied in the presence of strong correlation [43][44][45] , as long as the Fermi-liquid theory and quasi-particle picture remain valid.…”